1
|
Shaw C, McLure A, Glass K. Modelling African swine fever introduction in diverse Australian feral pig populations. Prev Vet Med 2024; 228:106212. [PMID: 38704921 DOI: 10.1016/j.prevetmed.2024.106212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/21/2023] [Accepted: 04/25/2024] [Indexed: 05/07/2024]
Abstract
African swine fever (ASF) is a viral disease that affects domestic and feral pigs. While not currently present in Australia, ASF outbreaks have been reported nearby in Indonesia, Timor-Leste, and Papua New Guinea. Feral pigs are found in all Australian states and territories and are distributed in a variety of habitats. To investigate the impacts of an ASF introduction event in Australia, we used a stochastic network-based metapopulation feral pig model to simulate ASF outbreaks in different regions of Australia. Outbreak intensity and persistence in feral pig populations was governed by local pig recruitment rates, population size, carcass decay period, and, if applicable, metapopulation topology. In Northern Australia, the carcass decay period was too short for prolonged persistence, while endemic transmission could possibly occur in cooler southern areas. Populations in Macquarie Marshes in New South Wales and in Namadgi National Park in the Australian Capital Territory had the highest rates of persistence. The regions had different modes of transmission that led to long-term persistence. Endemic Macquarie Marshes simulations were characterised by rapid transmission caused by high population density that required a fragmented metapopulation to act as a bottleneck to slow transmission. Endemic simulations in Namadgi, with low density and relatively slow transmission, relied on large, well-connected populations coupled with long carcass decay times. Despite the potential for endemic transmission, both settings required potentially unlikely population sizes and dynamics for prolonged disease survival.
Collapse
Affiliation(s)
- Callum Shaw
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia.
| | - Angus McLure
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia
| | - Kathryn Glass
- National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT, Australia
| |
Collapse
|
2
|
Matsumoto N, Ward MP, Halasa T, Schemann K, Khounsy S, Douangngeun B, Thepagna W, Phommachanh P, Siengsanan-Lamont J, Young JR, Toribio JALML, Bush RD, Blacksell SD. Novel estimation of African swine fever transmission parameters within smallholder villages in Lao P.D.R. Trop Anim Health Prod 2024; 56:166. [PMID: 38758410 PMCID: PMC11101325 DOI: 10.1007/s11250-024-04012-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 05/02/2024] [Indexed: 05/18/2024]
Abstract
African Swine Fever (ASF) disease transmission parameters are crucial for making response and control decisions when faced with an outbreak, yet they are poorly quantified for smallholder and village contexts within Southeast Asia. Whilst disease-specific factors - such as latent and infectious periods - should remain reasonably consistent, host, environmental and management factors are likely to affect the rate of disease spread. These differences are investigated using Approximate Bayesian Computation with Sequential Monte-Carlo methods to provide disease parameter estimates in four naïve pig populations in villages of Lao People's Democratic Republic. The villages represent smallholder pig farmers of the Northern province of Oudomxay and the Southern province of Savannakhet, and the model utilised field mortality data to validate the transmission parameter estimates over the course of multiple model generations. The basic reproductive number between-pigs was estimated to range from 3.08 to 7.80, whilst the latent and infectious periods were consistent with those published in the literature for similar genotypes in the region (4.72 to 6.19 days and 2.63 to 5.50 days, respectively). These findings demonstrate that smallholder village pigs interact similarly to commercial pigs, however the spread of disease may occur slightly slower than in commercial study groups. Furthermore, the findings demonstrated that despite diversity across the study groups, the disease behaved in a consistent manner. This data can be used in disease control programs or for future modelling of ASF in smallholder contexts.
Collapse
Affiliation(s)
- Nina Matsumoto
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia
| | - Michael P Ward
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia
| | - Tariq Halasa
- Section of Animal Welfare and Disease Control, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kathrin Schemann
- Sydney Informatics Hub, The University of Sydney, Camperdown, NSW, Australia
| | - Syseng Khounsy
- National Animal Health Laboratory, Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao People's Democratic Republic
| | - Bounlom Douangngeun
- National Animal Health Laboratory, Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao People's Democratic Republic
| | - Watthana Thepagna
- National Animal Health Laboratory, Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao People's Democratic Republic
| | - Phouvong Phommachanh
- National Animal Health Laboratory, Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao People's Democratic Republic
| | - Jarunee Siengsanan-Lamont
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - James R Young
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jenny-Ann L M L Toribio
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia
| | - Russell D Bush
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia
| | - Stuart D Blacksell
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, NSW, 2570, Australia.
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine & Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Mahosot Hospital, Vientiane, Lao People's Democratic Republic.
| |
Collapse
|
3
|
Gervasi V, Masiulis M, Bušauskas P, Bellini S, Guberti V. Optimizing Vaccination Strategies against African Swine Fever Using Spatial Data from Wild Boars in Lithuania. Viruses 2024; 16:153. [PMID: 38275963 PMCID: PMC10820490 DOI: 10.3390/v16010153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/09/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
African swine fever (ASF) is one of the most severe suid diseases, impacting the pig industry and wild suid populations. Once an ASF vaccine is available, identifying a sufficient density of vaccination fields will be crucial to achieve eradication success. In 2020-2023, we live-trapped and monitored 27 wild boars in different areas of Lithuania, in which the wild boars were fed at artificial stations. We built a simulation study to estimate the probability of a successful ASF vaccination as a function of different eco-epidemiological factors. The average 32-day home range size across all individuals was 16.2 km2 (SD = 16.9). The wild boars made frequent visits of short durations to the feeding sites rather than long visits interposed by long periods of absence. A feeding site density of 0.5/km2 corresponded to an expected vaccination rate of only 20%. The vaccination probability increased to about 75% when the feeding site density was 1.0/km2. Our results suggest that at least one vaccination field/km2 should be used when planning an ASF vaccination campaign to ensure that everyone in the population has at least 5-10 vaccination sites available inside the home range. Similar studies should be conducted in the other ecological contexts in which ASF is present today or will be present in the future, with the objective being to estimate a context-specific relationship between wild boar movement patterns and an optimal vaccination strategy.
Collapse
Affiliation(s)
- Vincenzo Gervasi
- Istituto Superiore per la Protezione e la Ricerca Ambientale, Via V. Brancati 60, 00144 Roma, Italy
| | - Marius Masiulis
- State Food and Veterinary Service of the Republic of Lithuania, Siesiku 19, 07170 Vilnius, Lithuania; (M.M.); (P.B.)
- Veterinary Academy, Lithuanian University of Health Sciences, Tilzes 18, 47181 Kaunas, Lithuania
| | - Paulius Bušauskas
- State Food and Veterinary Service of the Republic of Lithuania, Siesiku 19, 07170 Vilnius, Lithuania; (M.M.); (P.B.)
| | - Silvia Bellini
- Istituto Zooprofilattico della Lombardia ed Emilia-Romagna, Via A. Bianchi 7/9, 25124 Brescia, Italy;
| | - Vittorio Guberti
- Istituto Superiore per la Protezione e la Ricerca Ambientale, Via Cà Fornacetta 9, 40064 Ozzano dell’Emilia, Italy;
| |
Collapse
|
4
|
Schambow RA, Hussain S, Antognoli MC, Kreindel S, Reyes R, Perez AM. Epidemiological Assessment of African Swine Fever Spread in the Dominican Republic. Pathogens 2023; 12:1414. [PMID: 38133297 PMCID: PMC10746036 DOI: 10.3390/pathogens12121414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 11/16/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023] Open
Abstract
Since African Swine Fever (ASF) was detected in the Dominican Republic in July 2021, it has negatively impacted the country's swine industry. Assessing the epidemiological situation is crucial to helping local authorities and industry stakeholders control the disease. Here, data on 155 reported outbreaks in the Dominican Republic from November 2022 to June 2023 were evaluated. Descriptive spatiotemporal analysis was performed to characterize disease distribution and spread, and between-herd R0 was calculated for the study period. The Knox test and a space-time permutation model were used to evaluate clustering. Data on clinical presentation, biosecurity measures, and suspected reasons for introduction were categorized and summarized. The majority (78%) of outbreaks occurred on backyard farms which generally had low biosecurity. Across farm types, the majority of pigs were still alive at the time of depopulation. Spatiotemporal findings and R0 estimates suggest an endemic pattern of disease geographically located centrally within the country. Clustering was detected even at small temporal and spatial distances due to outbreaks amongst neighboring backyard farms. These results provide critical information on the current state of the ASF epidemic in the Dominican Republic and will aid government officials and swine industry leaders in developing effective ASF control strategies.
Collapse
Affiliation(s)
- Rachel A. Schambow
- Center for Animal Health and Food Safety, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA; (S.H.); (A.M.P.)
| | - Syed Hussain
- Center for Animal Health and Food Safety, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA; (S.H.); (A.M.P.)
| | - Maria C. Antognoli
- International Services Action Programs, Animal Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, CO 80526, USA; (M.C.A.); (S.K.)
| | - Silvia Kreindel
- International Services Action Programs, Animal Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, CO 80526, USA; (M.C.A.); (S.K.)
| | - Raysa Reyes
- Instituto del Estudio de las Enfermedades Zoonóticas, Universidad Autónoma de Santo Domingo, Santo Domingo 10904, Dominican Republic;
| | - Andres M. Perez
- Center for Animal Health and Food Safety, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA; (S.H.); (A.M.P.)
| |
Collapse
|
5
|
Gao Y, Boklund AE, Nielsen LH, Alban L, de Jong MCM. Estimating the impact of low temperature on African swine fever virus transmission through contaminated environments. Prev Vet Med 2023; 219:105991. [PMID: 37678000 DOI: 10.1016/j.prevetmed.2023.105991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 06/07/2023] [Accepted: 08/06/2023] [Indexed: 09/09/2023]
Abstract
African Swine Fever Virus (ASFV) is the cause of an infectious disease in pigs, which is difficult to control. Long viability of ASFV has been shown for several contaminated materials, especially under low temperature. Therefore, when pigs are exposed to a contaminated environment, new infections could occur without the presence of infectious individuals. For example, a contaminated, poorly washed, empty livestock vehicle poses a risk to the next load of pigs. A quantitative stochastic environmental transmission model was applied to simulate the change in environmental contamination levels over time and calculate the epidemic parameters through exposure-based estimation. Due to the lack of experimental data on environmental transmission at low temperatures, we performed a non-linear fit of the decay rate parameter with temperature based on a literature review. Eventually, 16 scenarios were constructed for different temperature (at 20 °C, 10 °C, 0 °C, or -10 °C) and duration of empty periods (1, 3, 5, or 7 days) after the environment had been contaminated. We quantified the variation in the contamination level of the environment over time and the probability of newly added recipients getting infected when exposed to the environment after the empty period. As a result, the transmission rate parameter for ASFV in pigs was estimated to be 1.53 (0.90, 2.45) day-1, the decay rate parameter to be 1.02 (0.73, 1.47) day-1 (at 21 °C), and the excretion rate parameter to be 2.70 (2.51, 3.02) day-1. Without washing and disinfecting, the environment required 9, 14, 24, 54 days to reach a low probability of causing at least one new case (<0.005) at 20 °C, 10 °C, 0 °C, -10 °C, respectively. In addition, the method proposed in this paper enables assessment of the effect of washing and disinfecting on ASFV environmental transmission. We conducted this study to better understand how the viability of ASFV at different temperatures could affect the infectivity in environmental transmission and to improve risk assessment and disease control strategies.
Collapse
Affiliation(s)
- Yuqi Gao
- Quantitative Veterinary Epidemiology group, Department of Animal Sciences, Wageningen University and Research, Wageningen, the Netherlands.
| | - Anette Ella Boklund
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lisbeth Harm Nielsen
- Department for Food Safety and Veterinary Issues, Danish Agriculture & Food Council, Copenhagen, Denmark
| | - Lis Alban
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department for Food Safety and Veterinary Issues, Danish Agriculture & Food Council, Copenhagen, Denmark
| | - Mart C M de Jong
- Quantitative Veterinary Epidemiology group, Department of Animal Sciences, Wageningen University and Research, Wageningen, the Netherlands
| |
Collapse
|
6
|
Pakotiprapha D, Kuhaudomlarp S, Tinikul R, Chanarat S. Bridging the Gap: Can COVID-19 Research Help Combat African Swine Fever? Viruses 2023; 15:1925. [PMID: 37766331 PMCID: PMC10536364 DOI: 10.3390/v15091925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/12/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
African swine fever (ASF) is a highly contagious and economically devastating disease affecting domestic pigs and wild boar, caused by African swine fever virus (ASFV). Despite being harmless to humans, ASF poses significant challenges to the swine industry, due to sudden losses and trade restrictions. The ongoing COVID-19 pandemic has spurred an unparalleled global research effort, yielding remarkable advancements across scientific disciplines. In this review, we explore the potential technological spillover from COVID-19 research into ASF. Specifically, we assess the applicability of the diagnostic tools, vaccine development strategies, and biosecurity measures developed for COVID-19 for combating ASF. Additionally, we discuss the lessons learned from the pandemic in terms of surveillance systems and their implications for managing ASF. By bridging the gap between COVID-19 and ASF research, we highlight the potential for interdisciplinary collaboration and technological spillovers in the battle against ASF.
Collapse
Affiliation(s)
| | | | | | - Sittinan Chanarat
- Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| |
Collapse
|
7
|
Martínez Avilés M, Bosch J, Ivorra B, Ramos ÁM, Ito S, Barasona JÁ, Sánchez-Vizcaíno JM. Epidemiological impacts of attenuated African swine fever virus circulating in wild boar populations. Res Vet Sci 2023; 162:104964. [PMID: 37531717 DOI: 10.1016/j.rvsc.2023.104964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 08/04/2023]
Abstract
African swine fever virus (ASFV) genotype II has been present in wild boar in the European Union since 2014. Control measures have reduced the incidence of the ASF, but highly virulent as well as attenuated ASFV strains continue to circulate. We present the intraherd epidemiological parameters of low and highly virulent ASFV in wild boar from experimental data, and for the first time, evaluate the impact of attenuated strain circulation through unique deterministic compartmental model simulations under various potential scenarios and hypotheses. Using an estimated PCR infectious threshold of TPCR = 36.4, we obtained several transmission parameters, like an Rx (experimental intraherd R0) value of 4.5. We also introduce two novel epidemiological parameters: infectious power and resistance power, which indicate the ability of animals to transmit the infection and the reduction in infectiousness after successive exposures to varying virulence strains, respectively. The presence of ASFV attenuated strains results in 4-17% of animals either remaining in a carrier state or becoming susceptible again when exposed to highly virulent ASFV for more than two years. The timing between exposures to viruses of different virulence also influences the percentage of animals that die or remain susceptible. The findings of this study can be utilized in epidemiological modelling and provide insight into important risk situations that should be considered for surveillance and future potential ASF vaccination strategies in wild boar.
Collapse
Affiliation(s)
- Marta Martínez Avilés
- Centro de Investigación en Sanidad Animal (Animal Health Research Centre), CISA-INIA, CSIC. Madrid, 28130, Spain.
| | - Jaime Bosch
- Animal Health Health Surveillance Centre (VISAVET) and Animal Health Department, Veterinary School Complutense University of Madrid (UCM), 28040, Spain
| | - Benjamin Ivorra
- Interdisciplinary Mathematics Institute (IMI), Complutense University of Madrid (UCM), 28040, Spain
| | - Ángel Manuel Ramos
- Interdisciplinary Mathematics Institute (IMI), Complutense University of Madrid (UCM), 28040, Spain
| | - Satoshi Ito
- Animal Health Health Surveillance Centre (VISAVET) and Animal Health Department, Veterinary School Complutense University of Madrid (UCM), 28040, Spain
| | - José Ángel Barasona
- Animal Health Health Surveillance Centre (VISAVET) and Animal Health Department, Veterinary School Complutense University of Madrid (UCM), 28040, Spain
| | - José Manuel Sánchez-Vizcaíno
- Animal Health Health Surveillance Centre (VISAVET) and Animal Health Department, Veterinary School Complutense University of Madrid (UCM), 28040, Spain
| |
Collapse
|
8
|
Kosowska A, Barasona JA, Barroso-Arévalo S, Blondeau Leon L, Cadenas-Fernández E, Sánchez-Vizcaíno JM. Low transmission risk of African swine fever virus between wild boar infected by an attenuated isolate and susceptible domestic pigs. Front Vet Sci 2023; 10:1177246. [PMID: 37635760 PMCID: PMC10448392 DOI: 10.3389/fvets.2023.1177246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
African swine fever (ASF) is a lethal infectious disease that affects domestic and wild pigs. This complex virus has already affected five continents and more than 70 countries and is considered to be the main threat to the global swine industry. The disease can potentially be transmitted directly through contact with infectious animals, or indirectly by means of contaminated feed or environments. Nevertheless, the knowledge regarding the transmission patterns of different ASF virus isolates at the wildlife-livestock interface is still limited. We have, therefore, assessed the potential transmission of an attenuated ASF virus isolate between infectious wild boar and directly exposed domestic pig. We registered 3,369 interspecific interactions between animals, which were brief and mostly initiated by wild boar. The major patterns observed during the study were head-to-head contact owing to sniffing, thus suggesting a high probability of pathogen transmission. However, only one of the five domestic pigs had a short period of viremia and became serologically positive for ASF virus antibodies. It was additionally discovered that the wild boar did not transmit the virulent virus isolate to the domestic pigs, which suggests that the presence of attenuated ASF virus isolates in affected areas may control the spreading of other more virulent isolates. These outcomes may help make decisions related to large-scale targeted management actions against ASF in field conditions.
Collapse
Affiliation(s)
- Aleksandra Kosowska
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| | - Jose A. Barasona
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| | - Sandra Barroso-Arévalo
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| | - Luisa Blondeau Leon
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| | - Estefanía Cadenas-Fernández
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| | - Jose M. Sánchez-Vizcaíno
- VISAVET Health Surveillance Center, Complutense University of Madrid, Madrid, Spain
- Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain
| |
Collapse
|
9
|
Oh SI, Bui NA, Bui VN, Dao DT, Cho A, Lee HG, Jung YH, Do YJ, Kim E, Bok EY, Hur TY, Lee HS. Pathobiological analysis of african swine fever virus contact-exposed pigs and estimation of the basic reproduction number of the virus in Vietnam. Porcine Health Manag 2023; 9:30. [PMID: 37386526 PMCID: PMC10311738 DOI: 10.1186/s40813-023-00330-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/26/2023] [Indexed: 07/01/2023] Open
Abstract
BACKGROUND African swine fever (ASF), caused by African swine fever virus (ASFV), is a fatal disease affecting wild and domestic pigs. Since China reported the first ASF outbreak in August 2018, ASFV has swept over the neighbouring Asian countries. However, studies involving experimental pig-to-pig ASFV transmission in Vietnam are lacking. The main objective of this experimental study was to demonstrate the pathobiological characteristics of ASFV contact-exposed pigs and estimate their basic reproduction number (R0) in Vietnam. Fifteen pigs were randomly divided into two groups: experimental (n = 10) and negative control (n = 5) groups. One pig in the experimental group was intramuscularly inoculated with ASFV strain from Vietnam in 2020 and housed with the uninoculated pigs during the study period (28 days). RESULTS The inoculated pig died 6 days post-inoculation, and the final survival rate was 90.0%. We started observing viremia and excretion of ASFV 10 days post-exposure in contact-exposed pigs. Unlike the surviving and negative control pigs, all necropsied pigs showed severe congestive splenomegaly and moderate-to-severe haemorrhagic lesions in the lymph nodes. The surviving pig presented with mild haemorrhagic lesions in the spleen and kidneys. We used Susceptible-Infectious-Removed models for estimating R0. The R0 values for exponential growth (EG) and maximum likelihood (ML) were calculated to be 2.916 and 4.015, respectively. In addition, the transmission rates (β) were estimated to be 0.729 (95% confidence interval [CI]: 0.379-1.765) for EG and 1.004 (95% CI: 0.283-2.450) for ML. CONCLUSIONS This study revealed pathobiological and epidemiological information in about pig-to-pig ASFV transmission. Our findings suggested that culling infected herds within a brief period of time may mitigate the spread of ASF outbreaks.
Collapse
Affiliation(s)
- Sang-Ik Oh
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
- Bio-Safety Research Institute and Laboratory of Veterinary Pathology, College of Veterinary Medicine, Jeonbuk National University, Iksan, 54596, Republic of Korea
| | - Ngoc Anh Bui
- Virology Department, National Institute of Veterinary Research, Hanoi, Vietnam
| | - Vuong Nghia Bui
- Virology Department, National Institute of Veterinary Research, Hanoi, Vietnam
| | - Duy Tung Dao
- Virology Department, National Institute of Veterinary Research, Hanoi, Vietnam
| | - Ara Cho
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Han Gyu Lee
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Young-Hun Jung
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Yoon Jung Do
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Eunju Kim
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Eun-Yeong Bok
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Tai-Young Hur
- Division of Animal Diseases & Health, Rural Development Administration, National Institute of Animal Science, Wanju, 55365, Republic of Korea
| | - Hu Suk Lee
- International Livestock Research Institute, Hanoi, Vietnam.
- College of Veterinary Medicine, Chungnam National University, Daejeon, 34134, Republic of Korea.
| |
Collapse
|
10
|
Buragohain L, Barman NN, Sen S, Bharali A, Dutta B, Choudhury B, Suresh KP, Gaurav S, Kumar R, Ali S, Kumar S, Singh Malik Y. Transmission of African Swine Fever Virus to the Wild Boars of Northeast India. Vet Q 2023; 43:1-10. [PMID: 36786106 PMCID: PMC10124978 DOI: 10.1080/01652176.2023.2178689] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
BACKGROUND India recorded the first outbreak of African swine fever (ASF) in North-eastern region (NER) in the year 2020. AIM The current study was undertaken to investigate the transmission of African swine fever virus (ASFV) in the wild boars of Northeast India, particularly of Assam. MATERIAL AND METHODS ASF suspected mortal tissue remains and blood samples of wild boars collected from different locations of Assam were screened for molecular detection of swine viruses which includes Classical swine fever virus, Porcine Circovirus 2, Porcine reproductive and respiratory syndrome virus and ASFV. RESULTS One sample each from Manas and Nameri National Parks were detected positive for ASFV. Besides this, one of the samples was positive for CSFV and one of the ASFV positive samples was also positive for PCV2. Several striking gross and microscopic alterations were noticed in different organs of ASFV infected animals. Sequencing and phylogenetic analysis of B646L gene confirmed the presence of ASFV genotype-II in wild boars. Circulation of similar genotype in domestic pigs of NER in the contemporary period as well as locations near to the aforementioned national parks indicates the transmission of ASFV from domestic to wild boars. CLINICAL RELEVANCE The detection of ASFV in the wild boars of Assam is alarming as it is an impending threat to pig population and other endangered species (particularly Pygmy hog), making it increasingly daunting to control the disease. CONCLUSION Chances are high for ASFV to become endemic in Assam region if stringent measures are not taken at proper time.
Collapse
Affiliation(s)
- Lukumoni Buragohain
- College of Veterinary Science, Assam Agricultural University, Guwahati, Assam, India
| | - Nagendra Nath Barman
- College of Veterinary Science, Assam Agricultural University, Guwahati, Assam, India
| | - Suparna Sen
- College of Veterinary Science, Assam Agricultural University, Guwahati, Assam, India
| | - Arpita Bharali
- College of Veterinary Science, Assam Agricultural University, Guwahati, Assam, India
| | - Biswajit Dutta
- College of Veterinary Science, Assam Agricultural University, Guwahati, Assam, India
| | | | | | | | - Rakesh Kumar
- Indian Institute of Technology, Guwahati, Assam, India
| | - Samsul Ali
- Wildlife Trust of India, CWRC, Kaziranga, Assam, India
| | - Sachin Kumar
- Indian Institute of Technology, Guwahati, Assam, India
| | - Yashpal Singh Malik
- College of Animal Biotechnology, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab, India
| |
Collapse
|
11
|
Le VP, Lan NT, Canevari JT, Villanueva-Cabezas JP, Padungtod P, Trinh TBN, Nguyen VT, Pfeiffer CN, Oberin MV, Firestone SM, Stevenson MA. Estimation of a Within-Herd Transmission Rate for African Swine Fever in Vietnam. Animals (Basel) 2023; 13:ani13040571. [PMID: 36830359 PMCID: PMC9951655 DOI: 10.3390/ani13040571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/22/2022] [Accepted: 01/24/2023] [Indexed: 02/10/2023] Open
Abstract
We describe results from a panel study in which pigs from a 17-sow African swine fever (ASF) positive herd in Thái Bình province, Vietnam, were followed over time to record the date of onset of ASF signs and the date of death from ASF. Our objectives were to (1) fit a susceptible-exposed-infectious-removed disease model to the data with transmission coefficients estimated using approximate Bayesian computation; (2) provide commentary on how a model of this type might be used to provide decision support for disease control authorities. For the outbreak in this herd, the median of the average latent period was 10 days (95% HPD (highest posterior density interval): 2 to 19 days), and the median of the average duration of infectiousness was 3 days (95% HPD: 2 to 4 days). The estimated median for the transmission coefficient was 3.3 (95% HPD: 0.4 to 8.9) infectious contacts per ASF-infectious pig per day. The estimated median for the basic reproductive number, R0, was 10 (95% HPD: 1.1 to 30). Our estimates of the basic reproductive number R0 were greater than estimates of R0 for ASF reported previously. The results presented in this study may be used to estimate the number of pigs expected to be showing clinical signs at a given number of days following an estimated incursion date. This will allow sample size calculations, with or without adjustment to account for less than perfect sensitivity of clinical examination, to be used to determine the appropriate number of pigs to examine to detect at least one with the disease. A second use of the results of this study would be to inform the equation-based within-herd spread components of stochastic agent-based and hybrid simulation models of ASF.
Collapse
Affiliation(s)
- Van Phan Le
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 10000, Vietnam
| | - Nguyen Thi Lan
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 10000, Vietnam
| | - Jose Tobias Canevari
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville 3010, Australia
| | - Juan Pablo Villanueva-Cabezas
- Department of Infectious Diseases, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Parkville 3000, Australia
- One Health Unit, The Nossal Institute for Global Health, The University of Melbourne, Parkville 3010, Australia
- Correspondence:
| | - Pawin Padungtod
- Food and Agriculture Organization of the United Nations, Hanoi 10000, Vietnam
| | | | - Van Tam Nguyen
- Institute of Veterinary Science and Technology, Hanoi 10000, Vietnam
| | - Caitlin N. Pfeiffer
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville 3010, Australia
| | - Madalene V. Oberin
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville 3010, Australia
| | - Simon M. Firestone
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville 3010, Australia
| | - Mark A. Stevenson
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville 3010, Australia
| |
Collapse
|
12
|
Poolkhet C, Kasemsuwan S, Thongratsakul S, Warrasuth N, Pamaranon N, Nuanualsuwan S. Prediction of the spread of African swine fever through pig and carcass movements in Thailand using a network analysis and diffusion model. PeerJ 2023; 11:e15359. [PMID: 37187529 PMCID: PMC10178211 DOI: 10.7717/peerj.15359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 04/16/2023] [Indexed: 05/17/2023] Open
Abstract
Background African swine fever (ASF) is a serious contagious viral disease of pigs that affects the pig industry. This study aimed to evaluate the possible African swine fever (ASF) distribution using network analysis and a diffusion model through live pig, carcass, and pig product movement data. Material and Methods Empirical movement data from Thailand for the year 2019 were used, and expert opinions were sought to evaluate network properties and the diffusion model. The networks were presented as live pig movement and carcass movement data at the provincial and district levels. For network analysis, a descriptive network analysis was performed using outdegree, indegree, betweenness, fragmentation, and power law distribution, and cutpoints were used to describe movement patterns. For the diffusion model, we simulated each network using spatially different infected locations, patterns, and initial infection sites. Based on expert opinions, the initial infection site, the probability of ASF occurrence, and the probability of the initial infected adopter were selected for the appropriated network. In this study, we also simulated networks under varying network parameters to predict the infection speed. Results and Conclusions The total number of movements recorded was 2,594,364. These were divided into 403,408 (403,408/2,594,364; 15.55%) for live pigs and 2,190,956 (2,190,956/2,594,364; 84.45%) for carcasses. We found that carcass movement at the provincial level showed the highest outdegree (mean = 342.554, standard deviation (SD) = 900.528) and indegree values (mean = 342.554, SD = 665.509). In addition, the outdegree and indegree presented similar mean values and the degree distributions of both district networks followed a power-law function. The network of live pigs at provincial level showed the highest value for betweenness (mean = 0.011, SD = 0.017), and the network of live pigs at provincial level showed the highest value for fragmentation (mean = 0.027, SD = 0.005). Our simulation data indicated that the disease occurred randomly due to live pig and carcass movements along the central and western regions of Thailand, causing the rapid spread of ASF. Without control measures, it could spread to all provinces within 5- and 3-time units and in all districts within 21- and 30-time units for the network of live pigs and carcasses, respectively. This study assists the authorities to plan control and preventive measures and limit economic losses caused by ASF.
Collapse
Affiliation(s)
- Chaithep Poolkhet
- Veterinary Public Health, Kasetsart University, Kamphaeng Saen, Nakhon Pathom, Thailand
| | - Suwicha Kasemsuwan
- Veterinary Public Health, Kasetsart University, Kamphaeng Saen, Nakhon Pathom, Thailand
| | - Sukanya Thongratsakul
- Veterinary Public Health, Kasetsart University, Kamphaeng Saen, Nakhon Pathom, Thailand
| | - Nattachai Warrasuth
- Department of Livestock Development, Ministry of Agriculture and Cooperatives, Bangkok, Thailand
| | - Nuttavadee Pamaranon
- Department of Livestock Development, Ministry of Agriculture and Cooperatives, Bangkok, Thailand
| | - Suphachai Nuanualsuwan
- Department of Veterinary Public Health, Chulalongkorn University, Bangkok, Thailand
- Center of Excellence for Food and Water Risk Analysis (FAWRA), Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
| |
Collapse
|
13
|
Mai NTA, Trinh TBN, Nguyen VT, Lai TNH, Le NP, Nguyen TTH, Nguyen TL, Ambagala A, Do DL, Le VP. Estimation of basic reproduction number (R0) of African swine fever (ASF) in mid-size commercial pig farms in Vietnam. Front Vet Sci 2022; 9:918438. [PMID: 36246317 PMCID: PMC9556723 DOI: 10.3389/fvets.2022.918438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 09/07/2022] [Indexed: 11/23/2022] Open
Abstract
African swine fever (ASF) is a devastating disease affecting the global swine industry. Recently, it has spread to many countries in Africa, Europe, Asia, and the Caribbean, leaving severe damage to local, regional, national, and global economies. Due to its highly complex molecular characteristics and pathogenesis, the development of a successful vaccine has been an unmet challenge. Therefore, ASF control relies solely on biosecurity, rapid detection, and elimination. Epidemiological information obtained from natural ASF outbreaks is critical for designing and implementing ASF control measures. Basic reproduction number (R0), an epidemiological metric used to describe the contagiousness or transmissibility of infectious agents, is an important epidemiological tool. In this study, we have calculated R0 for the in-farm spread of ASF among fattening pigs and sows in two midsize commercial pig farms, HY1 and HY2, that practice the spot removal approach in controlling ASF outbreaks in Vietnam. The R0 values for the sows and fattening pigs were 1.78 (1.35–2.35) and 4.76 (4.18–5.38) for HY1 and 1.55 (1.08–2.18) and 3.8 (3.33–4.28) for HY2. This is the first study to evaluate the transmission potential of ASF in midsize commercial pig farms in Vietnam. Based on the R0 values, we predict that the spot removal approach could be used to successfully control ASF outbreaks in midsize commercial sow barns but not in fattening pens.
Collapse
Affiliation(s)
- Nguyen Tuan Anh Mai
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Thi Bich Ngoc Trinh
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Van Tam Nguyen
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Thi Ngoc Ha Lai
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Nam Phuong Le
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Thi Thu Huyen Nguyen
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
- Animal Science and Veterinary Medicine Faculty, Bac Giang Agriculture and Forestry University, Bac Giang, Vietnam
| | - Thi Lan Nguyen
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Aruna Ambagala
- National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Winnipeg, MB, Canada
| | - Duc Luc Do
- College of Animal Sciences, Vietnam National University of Agriculture, Hanoi, Vietnam
| | - Van Phan Le
- College of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
| |
Collapse
|
14
|
Dankwa EA, Lambert S, Hayes S, Thompson RN, Donnelly CA. Stochastic modelling of African swine fever in wild boar and domestic pigs: Epidemic forecasting and comparison of disease management strategies. Epidemics 2022; 40:100622. [PMID: 36041286 DOI: 10.1016/j.epidem.2022.100622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 07/21/2022] [Accepted: 08/10/2022] [Indexed: 11/25/2022] Open
Abstract
African swine fever (ASF), caused by the African swine fever virus (ASFV), is highly virulent in domestic pigs and wild boar (Sus scrofa), causing up to 100% mortality. The recent epidemic of ASF in Europe has had a serious economic impact and poses a threat to global food security. Unfortunately, there is no effective treatment or vaccine against ASFV, limiting the available disease management strategies. Mathematical models allow us to further our understanding of infectious disease dynamics and evaluate the efficacy of disease management strategies. The ASF Challenge, organised by the French National Research Institute for Agriculture, Food, and the Environment, aimed to expand the development of ASF transmission models to inform policy makers in a timely manner. Here, we present the model and associated projections produced by our team during the challenge. We developed a stochastic model combining transmission between wild boar and domestic pigs, which was calibrated to synthetic data corresponding to different phases describing the epidemic progression. The model was then used to produce forward projections describing the likely temporal evolution of the epidemic under various disease management scenarios. Despite the interventions implemented, long-term projections forecasted persistence of ASFV in wild boar, and hence repeated outbreaks in domestic pigs. A key finding was that it is important to consider the timescale over which different measures are evaluated: interventions that have only limited effectiveness in the short term may yield substantial long-term benefits. Our model has several limitations, partly because it was developed in real-time. Nonetheless, it can inform understanding of the likely development of ASF epidemics and the efficacy of disease management strategies, should the virus continue its spread in Europe.
Collapse
Affiliation(s)
| | - Sébastien Lambert
- Centre for Emerging, Endemic and Exotic Diseases, Department of Pathobiology and Population Sciences, Royal Veterinary College, University of London, United Kingdom
| | - Sarah Hayes
- Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, United Kingdom
| | - Robin N Thompson
- Mathematics Institute, University of Warwick, Coventry, United Kingdom; Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - Christl A Donnelly
- Department of Statistics, University of Oxford, Oxford, United Kingdom; Department of Infectious Disease Epidemiology, Faculty of Medicine, School of Public Health, Imperial College London, United Kingdom.
| |
Collapse
|
15
|
Mai TN, Sekiguchi S, Huynh TML, Cao TBP, Le VP, Dong VH, Vu VA, Wiratsudakul A. Dynamic Models of Within-Herd Transmission and Recommendation for Vaccination Coverage Requirement in the Case of African Swine Fever in Vietnam. Vet Sci 2022; 9:vetsci9060292. [PMID: 35737344 PMCID: PMC9228824 DOI: 10.3390/vetsci9060292] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/05/2022] [Accepted: 06/12/2022] [Indexed: 01/09/2023] Open
Abstract
African swine fever (ASF) is a highly contagious disease that is caused by the ASF virus (ASFV) with a high fatality rate in domestic pigs resulting in a high socio-economic impact. The pig business in Vietnam was recently affected by ASF for the first time. This study thus aimed to develop a disease dynamic model to explain how ASFV spreads in Vietnamese pig populations and suggest a protective vaccine coverage level required to prevent future outbreaks. The outbreak data were collected from ten private small-scale farms within the first wave of ASF outbreaks in Vietnam. Three methods were used to estimate the basic reproduction number (R0), including the exponential growth method, maximum likelihood method, and attack rate method. The average R0 values were estimated at 1.49 (95%CI: 1.05–2.21), 1.58 (95%CI: 0.92–2.56), and 1.46 (95%CI: 1.38–1.57), respectively. Based on the worst-case scenario, all pigs in a herd would be infected and removed within 50 days. We suggest vaccinating at least 80% of pigs on each farm once a commercially approved ASF vaccine is available. However, an improvement in biosecurity levels in small-scale farms is still greatly encouraged to prevent the introduction of the virus.
Collapse
Affiliation(s)
- Thi Ngan Mai
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 100000, Vietnam; (T.N.M.); (T.M.L.H.); (T.B.P.C.); (V.P.L.); (V.H.D.)
| | - Satoshi Sekiguchi
- Department of Veterinary Science, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan;
- Center for Animal Disease Control, University of Miyazaki, Miyazaki 889-2192, Japan
| | - Thi My Le Huynh
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 100000, Vietnam; (T.N.M.); (T.M.L.H.); (T.B.P.C.); (V.P.L.); (V.H.D.)
| | - Thi Bich Phuong Cao
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 100000, Vietnam; (T.N.M.); (T.M.L.H.); (T.B.P.C.); (V.P.L.); (V.H.D.)
| | - Van Phan Le
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 100000, Vietnam; (T.N.M.); (T.M.L.H.); (T.B.P.C.); (V.P.L.); (V.H.D.)
| | - Van Hieu Dong
- Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 100000, Vietnam; (T.N.M.); (T.M.L.H.); (T.B.P.C.); (V.P.L.); (V.H.D.)
| | - Viet Anh Vu
- Faculty of Animal Science, Vietnam National University of Agriculture, Hanoi 100000, Vietnam;
| | - Anuwat Wiratsudakul
- Department of Clinical Sciences and Public Health, Faculty of Veterinary Science, Mahidol University, Nakhon Pathom 73170, Thailand
- The Monitoring and Surveillance Center for Zoonotic Diseases in Wildlife and Exotic Animals, Faculty of Veterinary Science, Mahidol University, Nakhon Pathom 73170, Thailand
- Correspondence: ; Tel.: +662-441-5242
| |
Collapse
|
16
|
Zhao H, Ren J, Wu S, Guo H, Du Y, Wan B, Ji P, Wu Y, Zhuang G, Zhang A, Zhang G. HRP-conjugated-nanobody-based cELISA for rapid and sensitive clinical detection of ASFV antibodies. Appl Microbiol Biotechnol 2022; 106:4269-4285. [PMID: 35612629 PMCID: PMC9130055 DOI: 10.1007/s00253-022-11981-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 05/09/2022] [Accepted: 05/13/2022] [Indexed: 11/26/2022]
Abstract
Abstract African swine fever (ASF), which is caused by the ASF virus (ASFV), is a highly contagious hemorrhagic disease that causes high mortality to domestic porcine and wild boars and brings huge economic losses to world swine industry. Due to the lack of an effective vaccine, the control of ASF must depend on early, efficient, and cost-effective detection and strict control and elimination strategies. Traditional serological testing methods are generally associated with high testing costs, complex operations, and high technical requirements. As a promising alternative diagnostic tool to traditional antibodies, nanobodies (Nb) have the advantages of simpler and faster generation, good stability and solubility, and high affinity and specificity, although the system is dependent on the immunization of Bactrian camels to obtain the specific VHH library of the target protein. The application of Nbs in the detection of ASFV antibodies has not yet been reported yet. Using a phage display technology, one Nb against the ASFV p54 protein that exhibited high specificity and affinity, Nb8, was successfully screened. A HEK293T cell line stably expressing Nb8-horseradish peroxidase (HRP) fusion protein was established using the lentiviral expression system. Following the optimization of the reaction conditions, the Nb8-HRP fusion protein was successfully used to establish a competitive enzyme-linked immunosorbent assay (cELISA) to detect ASFV-specific antibodies in pig serum, for the first time. There was no cross-reaction with healthy pig serum, porcine pseudorabies virus (PRV), porcine reproductive and respiratory syndrome virus (PRRSV), classical swine fever virus (CSFV), porcine epidemic diarrhea virus (PEDV), and classical swine fever virus (CSFV) positive sera. The optimal cut-off value for the cELISA by ROC analysis was 52.5%. A total of 209 serum samples were tested using the developed cELISA and a commercial ELISA kit. The results showed that the relative specificity of the cELISA was 98.97%, and the relative sensitivity of the cELISA was 93.3%, with the percent agreement between the two ELISA methods being 98.56%. In conclusion, a specific, sensitive, and repeatable cELISA was successfully developed based on the Nb8 as a probe, providing a promising method for the detection of anti-ASFV antibodies in clinical pig serum. Key points • We successfully screened a specific, high affinity nanobody against ASFV p54 protein. • We establish a method for continuous and stable expression of Nb-HRP fusion protein using a lentiviral packaging system. • We establish a nanobody cELISA detection method that can monitor an ASF infection. Supplementary Information The online version contains supplementary material available at 10.1007/s00253-022-11981-4.
Collapse
Affiliation(s)
- Huijun Zhao
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Jiahui Ren
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Shuya Wu
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Haoran Guo
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Yongkun Du
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Bo Wan
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Pengchao Ji
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Yanan Wu
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Guoqing Zhuang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China
| | - Angke Zhang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China.
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China.
| | - Gaiping Zhang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China.
- International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, Henan, China.
- Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Academy of Agricultural Sciences, Zhengzhou, 450002, Henan, China.
| |
Collapse
|
17
|
Malladi S, Ssematimba A, Bonney PJ, St Charles KM, Boyer T, Goldsmith T, Walz E, Cardona CJ, Culhane MR. Predicting the time to detect moderately virulent African swine fever virus in finisher swine herds using a stochastic disease transmission model. BMC Vet Res 2022; 18:84. [PMID: 35236347 PMCID: PMC8889644 DOI: 10.1186/s12917-022-03188-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 02/24/2022] [Indexed: 11/10/2022] Open
Abstract
Background African swine fever (ASF) is a highly contagious and devastating pig disease that has caused extensive global economic losses. Understanding ASF virus (ASFV) transmission dynamics within a herd is necessary in order to prepare for and respond to an outbreak in the United States. Although the transmission parameters for the highly virulent ASF strains have been estimated in several articles, there are relatively few studies focused on moderately virulent strains. Using an approximate Bayesian computation algorithm in conjunction with Monte Carlo simulation, we have estimated the adequate contact rate for moderately virulent ASFV strains and determined the statistical distributions for the durations of mild and severe clinical signs using individual, pig-level data. A discrete individual based disease transmission model was then used to estimate the time to detect ASF infection based on increased mild clinical signs, severe clinical signs, or daily mortality. Results Our results indicate that it may take two weeks or longer to detect ASF in a finisher swine herd via mild clinical signs or increased mortality beyond levels expected in routine production. A key factor contributing to the extended time to detect ASF in a herd is the fairly long latently infected period for an individual pig (mean 4.5, 95% P.I., 2.4 - 7.2 days). Conclusion These transmission model parameter estimates and estimated time to detection via clinical signs provide valuable information that can be used not only to support emergency preparedness but also to inform other simulation models of evaluating regional disease spread.
Collapse
Affiliation(s)
- Sasidhar Malladi
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| | - Amos Ssematimba
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA. .,Department of Mathematics, Faculty of Science, Gulu University, Gulu, Uganda.
| | - Peter J Bonney
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| | | | - Timothy Boyer
- Center for Epidemiology and Animal Health, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, Colorado, USA
| | - Timothy Goldsmith
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| | - Emily Walz
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| | - Carol J Cardona
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| | - Marie R Culhane
- Secure Food Systems Team, University of Minnesota, Saint Paul, MN, 55108, USA
| |
Collapse
|
18
|
Ewing DA, Pooley CM, Gamado KM, Porphyre T, Marion G. Exact Bayesian inference of epidemiological parameters from mortality data: application to African swine fever virus. J R Soc Interface 2022; 19:20220013. [PMID: 35259955 PMCID: PMC8905154 DOI: 10.1098/rsif.2022.0013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Pathogens such as African swine fever virus (ASFV) are an increasing threat to global livestock production with implications for economic well-being and food security. Quantification of epidemiological parameters, such as transmission rates and latent and infectious periods, is critical to inform efficient disease control. Parameter estimation for livestock disease systems is often reliant upon transmission experiments, which provide valuable insights in the epidemiology of disease but which may also be unrepresentative of at-risk populations and incur economic and animal welfare costs. Routinely collected mortality data are a potential source of readily available and representative information regarding disease transmission early in outbreaks. We develop methodology to conduct exact Bayesian parameter inference from mortality data using reversible jump Markov chain Monte Carlo incorporating multiple routes of transmission (e.g. within-farm secondary and background transmission from external sources). We use this methodology to infer epidemiological parameters for ASFV using data from outbreaks on nine farms in the Russian Federation. This approach improves inference on transmission rates in comparison with previous methods based on approximate Bayesian computation, allows better estimation of time of introduction and could readily be applied to other outbreaks or pathogens.
Collapse
Affiliation(s)
- David A Ewing
- Biomathematics and Statistics Scotland, James Clerk Maxwell Building, The King's Buildings, Edinburgh, UK
| | - Christopher M Pooley
- Biomathematics and Statistics Scotland, James Clerk Maxwell Building, The King's Buildings, Edinburgh, UK
| | - Kokouvi M Gamado
- Biomathematics and Statistics Scotland, James Clerk Maxwell Building, The King's Buildings, Edinburgh, UK
| | - Thibaud Porphyre
- The Epidemiology, Economics and Risk Assessment (EERA) Group, The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, UK.,Université de Lyon, Université Lyon 1, CNRS, VetAgro Sup, Laboratoire de Biométrie et Biologie Evolutive, Marcy l'Étoile, France
| | - Glenn Marion
- Biomathematics and Statistics Scotland, James Clerk Maxwell Building, The King's Buildings, Edinburgh, UK
| |
Collapse
|
19
|
Li J, Jin Z, Wang Y, Sun X, Xu Q, Kang J, Huang B, Zhu H. Data-driven dynamical modelling of the transmission of African swine fever in a few places in China. Transbound Emerg Dis 2021; 69:e646-e658. [PMID: 34655504 DOI: 10.1111/tbed.14345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 09/29/2021] [Indexed: 11/26/2022]
Abstract
Since the outbreak of African swine fever (ASF) in Shengyang, it has continued spreading in China. In the early stage of the epidemic, multi-point and concentrated outbreaks were mainly in the swill feeding areas. In this paper, we developed compartmental models to investigate the transmission of ASF in several raising units including Guquan, Jinba and Liancheng. Using the data collected from these three infected premises, we calibrated the models to estimate that the average incubation period was between 8 and 11 days, the onset period was about 2-3 days and the basic reproductive number was about 4.83-11.90. We also estimated the infection on the day before culling to be 45.24% (Guquan), 89.20% (Jinba) and 16.35% (Liancheng), respectively. The infection rate of Guquan could reach about 74.8% if culling were postponed by 2 days. We found that the infection was significantly higher than the morbidities (22.11% (Guquan), 49.35% (Jinba) and 12.94% (Liancheng)) calculated by actual statistical data. Besides, we simulated and compared the control effect of stopping transport, disinfecting, stopping swill and culling. Our findings suggest that any single measure was not enough to prevent the spread of ASF on a regional level but the combined measures is the key. Under the current situation, fully culling was recognized as most effective in controlling the epidemic, despite the culling of uninfected pigs.
Collapse
Affiliation(s)
- Juan Li
- Complex Systems Research Center, Shanxi University, Taiyuan, Shanxi, China.,China Animal Health and Epidemiology Center, Qingdao, China.,Laboratory of Mathematical Parallel Systems (LAMPS) and Canadian Centre for Diseases Modeling (CCDM), Department of Mathematics and Statistics, York University, Toronto, Canada
| | - Zhen Jin
- Complex Systems Research Center, Shanxi University, Taiyuan, Shanxi, China.,Shanxi Key Laboratory of Mathematical Techniques and Big Data Analysis on Disease Control and Prevention, Shanxi University, Taiyuan, Shanxi, China
| | - Youming Wang
- China Animal Health and Epidemiology Center, Qingdao, China
| | - Xiangdong Sun
- China Animal Health and Epidemiology Center, Qingdao, China
| | - Quangang Xu
- China Animal Health and Epidemiology Center, Qingdao, China
| | - Jingli Kang
- China Animal Health and Epidemiology Center, Qingdao, China
| | - Baoxu Huang
- China Animal Health and Epidemiology Center, Qingdao, China
| | - Huaiping Zhu
- Laboratory of Mathematical Parallel Systems (LAMPS) and Canadian Centre for Diseases Modeling (CCDM), Department of Mathematics and Statistics, York University, Toronto, Canada
| |
Collapse
|
20
|
Glazunova AA, Korennoy FI, Sevskikh TA, Lunina DA, Zakharova OI, Blokhin AA, Karaulov AK, Gogin AE. Risk Factors of African Swine Fever in Domestic Pigs of the Samara Region, Russian Federation. Front Vet Sci 2021; 8:723375. [PMID: 34504890 PMCID: PMC8421595 DOI: 10.3389/fvets.2021.723375] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/02/2021] [Indexed: 11/19/2022] Open
Abstract
African swine fever (ASF) is an incurable viral disease of domestic and wild pigs. A large-scale spread of ASF began in Eurasia in 2007 and has affected territories from Belgium to the Far East, occurring as both local- and regional-level epidemics. In 2020, a massive ASF epidemic emerged in the southeastern region of European Russia in the Samara Oblast and included 41 outbreaks of ASF in domestic pigs and 40 cases in wild boar. The Samara Oblast is characterized by a relatively low density of wild boar (0.04–0.05 head/km2) and domestic pigs (1.1–1.3 head/km2), with a high prevalence of small-scale productions (household farms). This study aims to understand the driving forces of the disease and perform a risk assessment for this region using complex epidemiological analyses. The socioeconomic and environmental factors of the ASF outbreak were explored using Generalized Linear Logistic Regression, where ASF infection status of the Samara Oblast districts was treated as a response variable. Presence of the virus in a district was found to be most significantly (p < 0.05) associated with the importation of live pigs from ASF-affected regions of Russia (OR = 371.52; 95% CI: 1.58–87290.57), less significantly (p < 0.1) associated with the density of smallholder farms (OR = 2.94; 0.82–10.59), volume of pork products' importation from ASF-affected regions of Russia (OR = 1.01; 1.00–1.02), summary pig population (OR = 1.01; 0.99–1.02), and insignificantly (p > 0.1) associated with presence of a common border with an ASF-affected region (OR = 89.2; 0.07–11208.64). No associations were found with the densities of pig and wild boar populations. The colocation analysis revealed no significant concentration of outbreaks in domestic pigs near cases in wild boar or vice versa. These results suggest that outbreaks notified in low biosecurity household farms were mainly associated with the transportation and trade of pigs and pork products from ASF-affected regions of Russia. The findings underline the importance of taking into account animal transportation data while conducting future studies to develop a risk map for the region and the rest of European Russia.
Collapse
Affiliation(s)
- Anastasia A Glazunova
- Federal Research Center for Virology and Microbiology, Branch in Samara, Samara, Russia
| | - Fedor I Korennoy
- Federal Center for Animal Health (FGBI ARRIAH), Vladimir, Russia.,Federal Research Center for Virology and Microbiology, Branch in Nizhny Novgorod, Nizhny Novgorod, Russia
| | | | - Daria A Lunina
- Federal Research Center for Virology and Microbiology, Branch in Samara, Samara, Russia
| | - Olga I Zakharova
- Federal Research Center for Virology and Microbiology, Branch in Nizhny Novgorod, Nizhny Novgorod, Russia
| | - Andrei A Blokhin
- Federal Research Center for Virology and Microbiology, Branch in Nizhny Novgorod, Nizhny Novgorod, Russia
| | - Anton K Karaulov
- Federal Center for Animal Health (FGBI ARRIAH), Vladimir, Russia
| | - Andrey E Gogin
- Federal Research Center for Virology and Microbiology, Pokrov, Russia
| |
Collapse
|
21
|
Rolesu S, Mandas D, Loi F, Oggiano A, Dei Giudici S, Franzoni G, Guberti V, Cappai S. African Swine Fever in Smallholder Sardinian Farms: Last 10 Years of Network Transmission Reconstruction and Analysis. Front Vet Sci 2021; 8:692448. [PMID: 34395576 PMCID: PMC8361751 DOI: 10.3389/fvets.2021.692448] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/30/2021] [Indexed: 12/20/2022] Open
Abstract
African swine fever (ASF) is a viral disease of suids that frequently leads to death. There are neither licensed vaccines nor treatments available, and even though humans are not susceptible to the disease, the serious socio-economic consequences associated with ASF have made it one of the most serious animal diseases of the last century. In this context, prevention and early detection play a key role in controlling the disease and avoiding losses in the pig value chain. Target biosecurity measures are a strong strategy against ASF virus (ASFV) incursions in farms nowadays, but to be efficient, these measures must be well-defined and easy to implement, both in commercial holdings and in the backyard sector. Furthermore, the backyard sector is of great importance in low-income settings, mainly for social and cultural practices that are highly specific to certain areas and communities. These contexts need to be addressed when authorities decide upon the provisions that should be applied in the case of infection or decide to combine them with strict preventive measures to mitigate the risk of virus spread. The need for a deeper understanding of the smallholder context is essential to prevent ASFV incursion and spread. Precise indications for pig breeding and risk estimation for ASFV introduction, spread and maintenance, taking into account the fact that these recommendations would be inapplicable in some contexts, are the keys for efficient target control measures. The aim of this work is to describe the 305 outbreaks that occurred in domestic pigs in Sardinia during the last epidemic season (2010-2018) in depth, providing essential features associated with intensive and backyard farms where the outbreaks occurred. In addition, the study estimates the average of secondary cases by kernel transmission network. Considering the current absence of ASF outbreaks in domestic pig farms in Sardinia since 2018, this work is a valid tool to specifically estimate the risk associated with different farm types and update our knowledge in this area.
Collapse
Affiliation(s)
- Sandro Rolesu
- Sardinian Regional Veterinary Epidemiological Observatory, Istituto Zooprofilattico Sperimentale della Sardegna “G. Pegreffi”, Cagliari, Italy
| | - Daniela Mandas
- Sardinian Regional Veterinary Epidemiological Observatory, Istituto Zooprofilattico Sperimentale della Sardegna “G. Pegreffi”, Cagliari, Italy
| | - Federica Loi
- Sardinian Regional Veterinary Epidemiological Observatory, Istituto Zooprofilattico Sperimentale della Sardegna “G. Pegreffi”, Cagliari, Italy
| | - Annalisa Oggiano
- Department of Animal Health, Istituto Zooprofilattico Sperimentale Della Sardegna, Sassari, Italy
| | - Silvia Dei Giudici
- Department of Animal Health, Istituto Zooprofilattico Sperimentale Della Sardegna, Sassari, Italy
| | - Giulia Franzoni
- Department of Animal Health, Istituto Zooprofilattico Sperimentale Della Sardegna, Sassari, Italy
| | - Vittorio Guberti
- ISPRA—Institute for Environmental Protection and Research, Rome, Italy
| | - Stefano Cappai
- Sardinian Regional Veterinary Epidemiological Observatory, Istituto Zooprofilattico Sperimentale della Sardegna “G. Pegreffi”, Cagliari, Italy
| |
Collapse
|
22
|
Gallardo C, Soler A, Nurmoja I, Cano-Gómez C, Cvetkova S, Frant M, Woźniakowski G, Simón A, Pérez C, Nieto R, Arias M. Dynamics of African swine fever virus (ASFV) infection in domestic pigs infected with virulent, moderate virulent and attenuated genotype II ASFV European isolates. Transbound Emerg Dis 2021; 68:2826-2841. [PMID: 34273247 DOI: 10.1111/tbed.14222] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 06/28/2021] [Accepted: 07/04/2021] [Indexed: 01/15/2023]
Abstract
This study aimed to compare the infection dynamics of three genotype II African swine fever viruses (ASFV) circulating in Europe. Eighteen domestic pigs divided into three groups were infected intramuscularly or by direct contact with two haemadsorbent ASFVs (HAD) from Poland (Pol16/DP/ OUT21) and Estonia (Est16/WB/Viru8), and with the Latvian non-HAD ASFV (Lv17/WB/Rie1). Parameters, such as symptoms, pathogenicity, and distribution of the virus in tissues, humoral immune response, and dissemination of the virus by blood, oropharyngeal and rectal routes, were investigated. The Polish ASFV caused a case of rapidly developing fatal acute disease, while the Estonian ASFV caused acute to sub-acute infections and two animals survived. In contrast, animals infected with the ASFV from Latvia developed a more subtle, mild, or even subclinical disease. Oral excretion was sporadic or even absent in the attenuated group, whereas in animals that developed an acute or sub-acute form of ASF, oral excretion began at the same time the ASFV was detected in the blood, or even 3 days earlier, and persisted up to 22 days. Regardless of virulence, blood was the main route of transmission of ASFV and infectious virus was isolated from persistently infected animals for at least 19 days in the attenuated group and up to 44 days in the group of moderate virulence. Rectal excretion was limited to the acute phase of infection. In terms of diagnostics, the ASFV genome was detected in contact pigs from oropharyngeal samples earlier than in blood, independently of virulence. Together with blood, both samples could allow to detect ASFV infection for a longer period. The results presented here provide quantitative data on the spread and excretion of ASFV strains of different virulence among domestic pigs that can help to better focus surveillance activities and, thus, increase the ability to detect ASF introductions earlier.
Collapse
Affiliation(s)
- Carmina Gallardo
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Alejandro Soler
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Imbi Nurmoja
- Estonian Veterinary and Food Laboratory, Estonian ASF-National reference laboratory (NRL), Kreutzwaldi, Tartu, Estonia
| | - Cristina Cano-Gómez
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Svetlana Cvetkova
- Laboratory of Microbiology and Pathology Institute of Food Safety, Animal Health and Enviroment, BIOR, Latvian ASF-National reference laboratory, Lejupes, Riga, Latvia
| | - Maciej Frant
- National Veterinary Research Institute, Poland ASF-National reference laboratory, Partyzantow, Pulawy, Poland
| | - Grzegorz Woźniakowski
- National Veterinary Research Institute, Poland ASF-National reference laboratory, Partyzantow, Pulawy, Poland.,Department of Diagnostics and Clinical Sciences, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University in Toruń, Lwowska, Toruń, Poland
| | - Alicia Simón
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Covadonga Pérez
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Raquel Nieto
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| | - Marisa Arias
- Centro de Investigación en Sanidad Animal, CISA, INIA-CSIC, European Union Reference Laboratory for African Swine Fever (EURL), Valdeolmos, Madrid, Spain
| |
Collapse
|
23
|
Gervasi V, Guberti V. African swine fever endemic persistence in wild boar populations: Key mechanisms explored through modelling. Transbound Emerg Dis 2021; 68:2812-2825. [PMID: 34255414 PMCID: PMC9292501 DOI: 10.1111/tbed.14194] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/17/2021] [Accepted: 06/17/2021] [Indexed: 11/27/2022]
Abstract
African swine fever (ASF) is a serious global concern from an ecological and economic point of view. While it is well established that its main transmission routes comprise contact between infected and susceptible animals and transmission through contaminated carcasses, the specific mechanism leading to its long‐term persistence is still not clear. Among others, a proposed mechanism involves the potential role of convalescent individuals, which would be able to shed the virus after the end of the acute infection. Using a spatially explicit, stochastic, individual‐based model, we tested: (1) if ASF can persist when transmission occurs only through infected wild boars and infected carcasses; (2) if the animals that survive ASF can play a relevant role in increasing ASF persistence chances; (3) how hunting pressure can affect the ASF probability to persist. The scenario in which only direct and carcass‐mediated transmission were contemplated had 52% probability of virus persistence 10 years after the initial outbreak. The inclusion of survivor‐mediated transmission corresponded to slightly higher persistence probabilities (57%). ASF prevalence during the endemic phase was generally low, ranging 0.1–0.2%. The proportion of seropositive individuals gradually decreased with time and ranged 4.5–6.6%. Our results indicate that direct and carcass‐mediated infection routes are sufficient to explain and justify the long‐term persistence of ASF at low wild boar density and the ongoing geographic expansion of the disease front in the European continent. During the initial years of an ASF outbreak, hunting should be carefully evaluated as a management tool, in terms of potential benefits and negative side‐effects, and combined with an intensive effort for the detection and removal of wild boar carcasses. During the endemic phase, further increasing hunting effort should not be considered as an effective strategy. Additional effort should be dedicated to finding and removing as many wild boar carcasses as possible.
Collapse
Affiliation(s)
- Vincenzo Gervasi
- Department of Wildlife, Institute for Environmental Protection and Research (ISPRA), Ozzano Emilia (BO), Italy
| | - Vittorio Guberti
- Department of Wildlife, Institute for Environmental Protection and Research (ISPRA), Ozzano Emilia (BO), Italy
| |
Collapse
|
24
|
Modeling the outbreak and control of African swine fever virus in large-scale pig farms. J Theor Biol 2021; 526:110798. [PMID: 34097915 DOI: 10.1016/j.jtbi.2021.110798] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 05/12/2021] [Accepted: 06/01/2021] [Indexed: 10/21/2022]
Abstract
African swine fever virus (ASFV) leads to a highly contagious, lethal and economically devastating disease among pigs. Since no effective treatment for the disease, it is crucial to investigate its transmission mechanism and control strategies in large-scale pig farms. We first established a toy model to explore ASFV spread in one pig unit. Then a switching patch model was developed to capture its spread from one initial epidemic pig house consecutively to others, even the whole farm. Assessing innocent culling rates of three large-scale epidemic pig farms in Jiangsu Province showed that it is unnecessary to slaughter all pigs in the farms compulsively. Then we explored how the disinfection and fixation of employees impact ASFV spread in the farms. To control ASFV, we can block or slow down its spreading by improving the efficiency of disinfection and decreasing employee population to some extend. We can also shrink potential areas to be infected by properly improving the matching refinement degree among employees and houses. Some essential requirements for large-scale pig farms are presented to reduce their ASFV spreading risk, which can be helpful for animal health authorities in establishing regulation to standardize large-scale pig farms.
Collapse
|
25
|
Mighell E, Ward MP. African Swine Fever spread across Asia, 2018-2019. Transbound Emerg Dis 2021; 68:2722-2732. [PMID: 33599077 DOI: 10.1111/tbed.14039] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/12/2021] [Accepted: 02/15/2021] [Indexed: 11/30/2022]
Abstract
African Swine Fever Virus (ASFV) is a highly contagious pathogen that causes disease in pigs, commonly characterized by acute haemorrhagic fever. Prior to August 2018, African Swine Fever (ASF) had not been reported in Asia, but has since spread throughout China, Mongolia, Korea, Vietnam, Laos, Cambodia, Myanmar, the Philippines, Hong Kong, Indonesia, Timor-Leste and Papua New Guinea. Using data collated from reports of confirmed cases, we applied spatio-temporal analysis to describe ASFV spread throughout Asia during its early phase-from 1 August 2018 (reported start date) to 31 December 2019-to provide an overview and comparative analysis. Analysis revealed a propagating epidemic of ASFV throughout Asia, with peaks corresponding to increased reports from China, Vietnam and Laos. Two clusters of reported outbreaks were found. During the epidemic, ASFV primarily spread from the North-East to the South-East: A larger, secondary cluster in the North-East represented earlier reports, while the smaller, primary cluster in the South-East was characterized by later reports. Significant differences in country-specific epidemics, morbidity, mortality and unit types were discovered. The initial number of outbreaks and enterprise size are likely predictors of the speed of spread and the effectiveness of ASFV stamping out procedures. Biosecurity methods, wild boar populations and the transportation of pigs and movement of infected fomites are discussed as likely risk factors for facilitating ASFV spread across Asia.
Collapse
Affiliation(s)
- Ellen Mighell
- Sydney School of Veterinary Science, The University of Sydney, Camden, NSW, Australia
| | - Michael P Ward
- Sydney School of Veterinary Science, The University of Sydney, Camden, NSW, Australia
| |
Collapse
|
26
|
Hayes BH, Andraud M, Salazar LG, Rose N, Vergne T. Mechanistic modelling of African swine fever: A systematic review. Prev Vet Med 2021; 191:105358. [PMID: 33930624 DOI: 10.1016/j.prevetmed.2021.105358] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 04/06/2021] [Accepted: 04/13/2021] [Indexed: 12/11/2022]
Abstract
The spread of African swine fever (ASF) poses a grave threat to the global swine industry. Without an available vaccine, understanding transmission dynamics is essential for designing effective prevention, surveillance, and intervention strategies. These dynamics can often be unraveled through mechanistic modelling. To examine the assumptions on transmission and objectives of the mechanistic models of ASF, a systematic review of the scientific literature was conducted. Articles were examined across multiple epidemiological and model characteristics, with filiation between models determined through the creation of a neighbor-joined tree using phylogenetic software. Thirty-four articles qualified for inclusion, with four main modelling objectives identified: estimating transmission parameters (11 studies), assessing determinants of transmission (7), examining consequences of hypothetical outbreaks (5), assessing alternative control strategies (11). Population-based (17), metapopulation (5), and individual-based (12) model frameworks were represented, with population-based and metapopulation models predominantly used among domestic pigs, and individual-based models predominantly represented among wild boar. The majority of models (25) were parameterized to the genotype II isolates currently circulating in Europe and Asia. Estimated transmission parameters varied widely among ASFV strains, locations, and transmission scale. Similarly, parameter assumptions between models varied extensively. Uncertainties on epidemiological and ecological parameters were usually accounted for to assess the impact of parameter values on the modelled infection trajectory. To date, almost all models are host specific, being developed for either domestic pigs or wild boar despite the fact that spillover events between domestic pigs and wild boar are evidenced to play an important role in ASF outbreaks. Consequently, the development of more models incorporating such transmission routes is crucial. A variety of codified and hypothetical control strategies were compared however they were all a priori defined interventions. Future models, built to identify the optimal contributions across many control methods for achieving specific outcomes should provide more useful information for policy-makers. Further, control strategies were examined in competition with each other, which is opposed to how they would actually be synergistically implemented. While comparing strategies is beneficial for identifying a rank-order efficacy of control methods, this structure does not necessarily determine the most effective combination of all available strategies. In order for ASFV models to effectively support decision-making in controlling ASFV globally, these modelling limitations need to be addressed.
Collapse
Affiliation(s)
- Brandon H Hayes
- UMR ENVT-INRAE IHAP, National Veterinary School of Toulouse, 31000, Toulouse, France; Epidemiology Health and Welfare Department, Ploufragan-Plouzané-Niort Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 22440, Ploufragan, France.
| | - Mathieu Andraud
- Epidemiology Health and Welfare Department, Ploufragan-Plouzané-Niort Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 22440, Ploufragan, France
| | - Luis G Salazar
- Epidemiology Health and Welfare Department, Ploufragan-Plouzané-Niort Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 22440, Ploufragan, France
| | - Nicolas Rose
- Epidemiology Health and Welfare Department, Ploufragan-Plouzané-Niort Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 22440, Ploufragan, France
| | - Timothée Vergne
- UMR ENVT-INRAE IHAP, National Veterinary School of Toulouse, 31000, Toulouse, France
| |
Collapse
|
27
|
Nielsen SS, Alvarez J, Bicout DJ, Calistri P, Depner K, Drewe JA, Garin-Bastuji B, Gonzales Rojas JL, Gortázar Schmidt C, Herskin M, Michel V, Miranda Chueca MÁ, Pasquali P, Roberts HC, Sihvonen LH, Spoolder H, Ståhl K, Velarde A, Viltrop A, Winckler C, De Clercq K, Klement E, Stegeman JA, Gubbins S, Antoniou SE, Broglia A, Van der Stede Y, Zancanaro G, Aznar I. Scientific Opinion on the assessment of the control measures of the category A diseases of Animal Health Law: African Swine Fever. EFSA J 2021; 19:e06402. [PMID: 33552298 PMCID: PMC7848183 DOI: 10.2903/j.efsa.2021.6402] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
EFSA received a mandate from the European Commission to assess the effectiveness of some of the control measures against diseases included in the Category A list according to Regulation (EU) 2016/429 on transmissible animal diseases (‘Animal Health Law’). This opinion belongs to a series of opinions where these control measures will be assessed, with this opinion covering the assessment of control measures for African Swine Fever (ASF). In this opinion, EFSA and the AHAW Panel of experts reviewed the effectiveness of: (i) clinical and laboratory sampling procedures, (ii) monitoring period and (iii) the minimum radius of the protection and surveillance zone, and the minimum length of time the measures should be applied in these zones. The general methodology used for this series of opinions has been published elsewhere; nonetheless, specific details of the model used for the assessment of the laboratory sampling procedures for ASF are presented here. Here, also, the transmission kernels used for the assessment of the minimum radius of the protection and surveillance zones are shown. Several scenarios for which these control measures had to be assessed were designed and agreed prior to the start of the assessment. In summary, several sampling procedures as described in the diagnostic manual for ASF were considered ineffective and a suggestion to exclude, or to substitute with more effective procedures was made. The monitoring period was assessed as non‐effective for several scenarios and a longer monitoring period was suggested to ensure detection of potentially infected herds. It was demonstrated that the surveillance zone comprises 95% of the infections from an affected establishment, and therefore is considered effective. Recommendations provided for each of the scenarios assessed aim to support the European Commission in the drafting of further pieces of legislation, as well as for plausible ad hoc requests in relation to ASF.
Collapse
|
28
|
Kosowska A, Cadenas-Fernández E, Barroso S, Sánchez-Vizcaíno JM, Barasona JA. Distinct African Swine Fever Virus Shedding in Wild Boar Infected with Virulent and Attenuated Isolates. Vaccines (Basel) 2020; 8:vaccines8040767. [PMID: 33339147 PMCID: PMC7765575 DOI: 10.3390/vaccines8040767] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 12/13/2020] [Accepted: 12/14/2020] [Indexed: 11/16/2022] Open
Abstract
Since the reappearance of African swine fever virus (ASFV), the disease has spread in an unprecedented animal pandemic in Eurasia. ASF currently constitutes the greatest global problem for the swine industry. The wild boar (Sus scrofa) in which the pathogen has established wild self-sustaining cycles, is a key reservoir for ASFV, signifying that there is an urgent need to develop an effective vaccine against this virus. Current scientific debate addresses whether live attenuated vaccines (LAVs), which have shown promising results in cross-protection of susceptible hosts, may be feasible for vaccinations carried out owing to safety concerns. The objective of this study was, therefore, to compare the ASFV shedding in wild boar infected with virulent and attenuated (LAV) isolates. Different shedding routes (oral fluid and feces) and viremia rates were characterized in wild boar inoculated with Lv17/WB/Rie1 isolate (n = 12) when compared to those inoculated with the virulent Armenia07 isolate (n = 17). In general, fewer animals infected with the Lv17/WB/Rie1 isolate tested positive for ASFV in blood, oral fluid, and feces in comparison to animals infected with the virulent Armenia07 isolate. The shedding patterns were characterized in order to understand the transmission dynamics. This knowledge will help evaluate the shedding of new LAV candidates in wild boar populations, including the comparison with gene deletion mutant LAVs, whose current results are promising.
Collapse
Affiliation(s)
- Aleksandra Kosowska
- VISAVET Health Surveillance Center, Complutense University of Madrid, 28040 Madrid, Spain; (E.C.-F.); (S.B.); (J.M.S.-V.)
- Department of Animal Health, Faculty of Veterinary, Complutense University of Madrid, 28040 Madrid, Spain
- Correspondence: (A.K.); (J.A.B.)
| | - Estefanía Cadenas-Fernández
- VISAVET Health Surveillance Center, Complutense University of Madrid, 28040 Madrid, Spain; (E.C.-F.); (S.B.); (J.M.S.-V.)
- Department of Animal Health, Faculty of Veterinary, Complutense University of Madrid, 28040 Madrid, Spain
| | - Sandra Barroso
- VISAVET Health Surveillance Center, Complutense University of Madrid, 28040 Madrid, Spain; (E.C.-F.); (S.B.); (J.M.S.-V.)
- Department of Animal Health, Faculty of Veterinary, Complutense University of Madrid, 28040 Madrid, Spain
| | - Jose M. Sánchez-Vizcaíno
- VISAVET Health Surveillance Center, Complutense University of Madrid, 28040 Madrid, Spain; (E.C.-F.); (S.B.); (J.M.S.-V.)
- Department of Animal Health, Faculty of Veterinary, Complutense University of Madrid, 28040 Madrid, Spain
| | - Jose A. Barasona
- VISAVET Health Surveillance Center, Complutense University of Madrid, 28040 Madrid, Spain; (E.C.-F.); (S.B.); (J.M.S.-V.)
- Department of Animal Health, Faculty of Veterinary, Complutense University of Madrid, 28040 Madrid, Spain
- Correspondence: (A.K.); (J.A.B.)
| |
Collapse
|
29
|
Abstract
African swine fever is a devastating disease that can result in death in almost all infected pigs. The continuing spread of African swine fever from Africa to Europe and recently to the high-pig production countries of China and others in Southeast Asia threatens global pork production and food security. The African swine fever virus is an unusual complex DNA virus and is not related to other viruses. This has presented challenges for vaccine development, and currently none is available. The virus is extremely well adapted to replicate in its hosts in the sylvatic cycle in East and South Africa. Its spread to other regions, with different wildlife hosts, climatic conditions, and pig production systems, has revealed unexpected epidemiological scenarios and different challenges for control. Here we review the epidemiology of African swine fever in these different scenarios and methods used for control. We also discuss progress toward vaccine development and research priorities to better understand this complex disease and improve control.
Collapse
Affiliation(s)
- Linda K Dixon
- The Pirbright Institute, Woking, Surrey GU24 0NF, United Kingdom;
| | - Karl Stahl
- Department of Disease Control and Epidemiology, National Veterinary Institute, SE-751 89 Uppsala, Sweden;
| | - Ferran Jori
- UMR CIRAD-INRA ASTRE (Animal, Health, Territories, Risks and Ecosystems) Department BIOS, Campus International de Baillarguet, 34398 Montpellier, Cedex 5, France; ,
| | - Laurence Vial
- UMR CIRAD-INRA ASTRE (Animal, Health, Territories, Risks and Ecosystems) Department BIOS, Campus International de Baillarguet, 34398 Montpellier, Cedex 5, France; ,
| | - Dirk U Pfeiffer
- Centre for Applied One Health Research and Policy Advice, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong SAR, PR China;
| |
Collapse
|
30
|
Faverjon C, Meyer A, Howden K, Long K, Peters L, Cameron A. Risk-based early detection system of African Swine Fever using mortality thresholds. Transbound Emerg Dis 2020; 68:1151-1161. [PMID: 32748561 DOI: 10.1111/tbed.13765] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/14/2020] [Accepted: 07/29/2020] [Indexed: 11/26/2022]
Abstract
African swine fever (ASF) is an infectious disease of swine causing major losses in the swine industry worldwide. Early detection of ASF is challenging because of the wide range of non-specific clinical signs produced and its relatively low contagiousness. Monitoring pig mortality is a promising approach for early detection of ASF, but such approach has been associated with delay in disease detection in large pig farms. The purpose of this study was to compare the effectiveness and suitability of early detection strategies for ASF in large commercial pig farms using mortality monitoring at the pen, room or barn level. The within-barn spread of the disease was modelled including the non-homogeneous probabilities of transmission within pens, between pens and between rooms. The performances of early detection surveillance based on mortality thresholds established for different epidemiological units were compared in terms of sensitivity, time to detection and number of false alarms per year. A barn with a capacity of 3,200 pigs divided into 8 rooms with 10 pens each containing 40 pigs per pen was used as an example. Our results show that using room- or pen-based mortality thresholds provided a time to detection of 8 days post-disease introduction. Similar detection performances could be achieved with barn-level mortality threshold but at the cost of an increased number of pigs to be tested each year. The different scenarios tested also show that barn characteristics such as baseline mortality rate and pen size had a limited impact on the pen-level mortality thresholds required for disease early detection. These results offer strong support for using mortality data for early detection of ASF not only in small pig herds but also in large commercial barns. Furthermore, the mortality thresholds defined in this study might be relevant to a wide range of pig production sites.
Collapse
Affiliation(s)
| | | | - Krista Howden
- One Health Scientific Solutions, Sherwood Park, Canada
| | | | | | | |
Collapse
|
31
|
Shi R, Li Y, Wang C. Stability analysis and optimal control of a fractional-order model for African swine fever. Virus Res 2020; 288:198111. [PMID: 32791169 DOI: 10.1016/j.virusres.2020.198111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 07/30/2020] [Accepted: 07/31/2020] [Indexed: 10/23/2022]
Abstract
In this paper, a basic fractional-order model is proposed to describe the transmission of African swine fever. Two cases are considered: constant control and optimal control. In the former case, the existence and uniqueness of positive solution is proved firstly; then the basic reproduction number and the sufficient conditions for the stability of two equilibriums are obtained by using the next generation matrix method and Lyapunov LaSalle's invariance principle. In the latter case, optimal control is considered. By using the Hamiltonian function and Pontryagin's maximum principle, the optimal control formula is obtained. In addition, some examples and numerical simulations (based on Adama-Bashforth-Moulton predictor-corrector method) are performed to verify the theoretical results. At last, we present some brief discussion and conclusion.
Collapse
Affiliation(s)
- Ruiqing Shi
- School of Mathematics and Computer Science, Shanxi Normal University, Linfen 041004, China.
| | - Yang Li
- School of Mathematics and Computer Science, Shanxi Normal University, Linfen 041004, China.
| | - Cuihong Wang
- School of Mathematics and Computer Science, Shanxi Normal University, Linfen 041004, China.
| |
Collapse
|
32
|
Meekins DA, Trujillo JD, Gaudreault NN, Morozov I, Pérez-Núñez D, Revilla Y, Richt JA. Long amplicon sequencing for improved genetic characterization of African swine fever virus. J Virol Methods 2020; 285:113946. [PMID: 32758620 DOI: 10.1016/j.jviromet.2020.113946] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 07/27/2020] [Accepted: 07/30/2020] [Indexed: 11/26/2022]
Abstract
African Swine Fever Virus (ASFV) causes a transmissible and fatal disease in pigs that is currently devastating global swine production. Efficient and economical collection of genetic data from ASFV field isolates is essential for bio-surveillance, to limit and control its spread, and to better understand ASF disease ecology. Standard genotyping and subtyping of ASFV field isolates is currently limited to a few variable regions within the ASFV genome. However, more extensive sequencing is necessary to better understand ASFV molecular evolution and identify regions relevant to genetic diversity. In this study, we developed a method for rapid and efficient next generation sequencing of approximately 40% of the ASFV genome using long PCR amplification of six different genomic regions. The amplified regions contain all segments currently used for genotyping and additional genes predicted to contribute to ASFV diversity. The primers used for amplification are broadly compatible with published ASFV genomes, permitting their use on relevant ASFV isolates. This methodology provides the enhanced depth of coverage of amplicon-based sequencing while mitigating complications associated with ASFV whole-genome sequencing. Implementation of this methodology could substantially increase the scale of ASFV genetic data collection, which is necessary to effectively monitor and combat this critical agricultural disease.
Collapse
Affiliation(s)
- David A Meekins
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Department of Diagnostic Medicine & Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Jessie D Trujillo
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Department of Diagnostic Medicine & Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Natasha N Gaudreault
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Department of Diagnostic Medicine & Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Igor Morozov
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Department of Diagnostic Medicine & Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Daniel Pérez-Núñez
- CBMSO-CSIC-UAM, C/Nicolás Cabrera 1, Campus de Cantoblanco, 28049, Madrid, Spain
| | - Yolanda Revilla
- CBMSO-CSIC-UAM, C/Nicolás Cabrera 1, Campus de Cantoblanco, 28049, Madrid, Spain
| | - Juergen A Richt
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Department of Diagnostic Medicine & Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA.
| |
Collapse
|
33
|
Schulz K, Conraths FJ, Blome S, Staubach C, Sauter-Louis C. African Swine Fever: Fast and Furious or Slow and Steady? Viruses 2019; 11:E866. [PMID: 31533266 PMCID: PMC6783890 DOI: 10.3390/v11090866] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/13/2019] [Accepted: 09/14/2019] [Indexed: 11/16/2022] Open
Abstract
Since the introduction of African swine fever (ASF) into Georgia in 2007, the disease has been spreading in an unprecedented way. Many countries that are still free from the disease fear the emergence of ASF in their territory either in domestic pigs or in wild boar. In the past, ASF was often described as being a highly contagious disease with mortality often up to 100%. However, the belief that the disease might enter a naïve population and rapidly affect the entire susceptible population needs to be critically reviewed. The current ASF epidemic in wild boar, but also the course of ASF within outbreaks in domestic pig holdings, suggest a constant, but relatively slow spread. Moreover, the results of several experimental and field studies support the impression that the spread of ASF is not always fast. ASF spread and its speed depend on various factors concerning the host, the virus, and also the environment. Many of these factors and their effects are not fully understood. For this review, we collated published information regarding the spreading speed of ASF and the factors that are deemed to influence the speed of ASF spread and tried to clarify some issues and open questions in this respect.
Collapse
Affiliation(s)
- Katja Schulz
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Franz Josef Conraths
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Sandra Blome
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Christoph Staubach
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Carola Sauter-Louis
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| |
Collapse
|
34
|
Lack of evidence for long term carriers of African swine fever virus - a systematic review. Virus Res 2019; 272:197725. [PMID: 31430503 DOI: 10.1016/j.virusres.2019.197725] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 08/15/2019] [Accepted: 08/16/2019] [Indexed: 11/23/2022]
Abstract
African swine fever (ASF) was first described in 1921 as a highly fatal and contagious disease which caused severe outbreaks among settlers' pigs in British East Africa. Since then the disease has expanded its geographical distribution and is currently present in large parts of Africa, Europe and Asia and considered a global threat. Although ASF is typically associated with very high case fatality rates, a certain proportion of infected animals will recover from the infection and survive. Early on it was speculated that such survivors may act as carriers of the virus, and the importance of such carries for disease persistence and spread has since then almost become an established truth. However, the scientific basis for such a role of carriers may be questioned. With this in mind, the objective of this study was to review the available literature in a systematic way and to evaluate the available scientific evidence. The selection of publications for the review was based on a database search, followed by a stepwise screening process in order to exclude duplicates and non-relevant publications based on pre-defined exclusion criteria. By this process the number of publications finally included was reduced from the 3664 hits identified in the initial database search to 39 publications, from which data was then extracted and analysed. Based on this it was clear that a definition of an ASF virus carrier is lacking, and that in general any survivor or seropositive animal has been referred to as carrier. It was also clear that evidence of any significant role of such a carrier is absent. Two types of "survivors" could be defined: 1) pigs that do not die but develop a persistent infection, characterised by periodic viraemia and often but not always accompanied by some signs of subacute to chronic disease, and 2) pigs which clear the infection independently of virulence of the virus, and which are not persistently infected and will not present with prolonged virus excretion. There is no evidence that suggests that any of these categories of survivors can be considered as "healthy" carriers, i.e. pigs that show no sign of disease but can transmit the virus to in-contact pigs. However, localized virus persistence in lymphoid tissues may occur to some extent in any of the categories of survivors, which in theory may cause infection after oral uptake. To what extent this is relevant in reality, however, can be questioned given the virus dose generally needed for oral infection.
Collapse
|
35
|
Asambe A, Sackey AKB, Tekdek LB. Sanitary measures in piggeries, awareness, and risk factors of African swine fever in Benue State, Nigeria. Trop Anim Health Prod 2019; 51:997-1001. [PMID: 30569230 PMCID: PMC6469624 DOI: 10.1007/s11250-018-1764-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Accepted: 11/20/2018] [Indexed: 11/26/2022]
Abstract
The present study describes assessment of sanitary measures in piggeries of Benue State, Nigeria, to identify the risk factors of African swine fever. Questionnaires were distributed to 74 respondents consisting of piggery owners and attendants in different piggeries across 12 local government areas (LGAs) to collect data for this study. Sanitary measures in piggeries were observed to be generally very poor, though respondents admitted being aware of ASF. Piggeries located within 1-km radius of a slaughter slab (OR = 9.2, 95% CI 3.0-28.8; p < 0.0001) and piggeries near refuse dump sites (OR = 3.0, 95% CI 1.0-9.5; p < 0.05) showed higher chances of African swine fever virus (ASFV) infection, while piggeries where farm workers wear their work clothes outside of the piggery premises (OR = 0.2, 95% CI 0.1-0.7; p < 0.01) indicate less chances of infection but had a significantly associated p value thus were identified as potential risk factors. The study concluded that pigs in Benue State are still at risk of an ASF outbreak. Proper sanitary and hygienic practices are advocated and emphasized in piggeries, while routine surveillance for African swine fever virus antibodies in pigs in Benue State is strongly recommended to provide a reliable reference database to plan for the prevention of any devastating ASF outbreak.
Collapse
Affiliation(s)
- A Asambe
- Department of Animal Science, Faculty of Agriculture and Agricultural Technology, Federal University Dutsina, Dutsina, Katsina State, P.M.B 5001, Nigeria.
| | - A K B Sackey
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
| | - L B Tekdek
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
| |
Collapse
|
36
|
Golnar AJ, Martin E, Wormington JD, Kading RC, Teel PD, Hamer SA, Hamer GL. Reviewing the Potential Vectors and Hosts of African Swine Fever Virus Transmission in the United States. Vector Borne Zoonotic Dis 2019; 19:512-524. [PMID: 30785371 PMCID: PMC6602103 DOI: 10.1089/vbz.2018.2387] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
African swine fever virus (ASFV) continues to threaten global animal health and agricultural biosecurity. Mitigating the establishment of ASFV in the United States (U.S.) is contingent on (1) the identification of arthropod vectors and vertebrate hosts that are capable of viral maintenance and transmission in the U.S. and (2) knowledge of vector-host associations that may permit transmission. We aggregated data on vector competence, host competence and tick–host associations by systematic review of published articles and collection records to identify species that may support the invasion of ASFV in the U.S. Three species of competent soft ticks occur in the U.S., Ornithodoros coriaceus, Ornithodoros turicata, and Ornithodoros puertoricensis, however, vector competence for the majority of soft ticks in the U.S. remains unknown. Three species of competent vertebrate hosts currently occur in the U.S.: domestic pigs (Sus scrofa domesticus), feral hogs (Sus scrofa), and common warthogs (Phacochoerus africanus). Hierarchical hazard categories based on vector competence, tick–host contact rates, and vector abundance were used to semiquantitatively rank U.S. soft tick species by their relative risk for contributing to ASFV transmission to identify which soft tick species are a priority for future studies. High-risk vector and host species identified in this study can be used to focus ASFV risk assessments in the U.S., guide targeted surveillance and control strategies, and proactively prepare for an ASFV incursion event. Results indicate O. coriaceus, O. turicata, and O. puertoricensis demonstrate the highest relative risk for contributing to ASFV transmission in the U.S., however, many gaps in knowledge exist preventing the full evaluation of at least 30 soft tick species in the U.S. Further study is required to identify soft tick vectors that interact with feral swine populations, elucidate vector competence, and further understand the biology of soft tick species.
Collapse
Affiliation(s)
- Andrew J Golnar
- 1 Texas A&M AgriLife Research, Department of Entomology, Texas A&M University, College Station, Texas
| | - Estelle Martin
- 1 Texas A&M AgriLife Research, Department of Entomology, Texas A&M University, College Station, Texas
| | - Jillian D Wormington
- 2 Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas
| | - Rebekah C Kading
- 3 Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, Colorado
| | - Pete D Teel
- 1 Texas A&M AgriLife Research, Department of Entomology, Texas A&M University, College Station, Texas
| | - Sarah A Hamer
- 2 Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas
| | - Gabriel L Hamer
- 1 Texas A&M AgriLife Research, Department of Entomology, Texas A&M University, College Station, Texas
| |
Collapse
|
37
|
Petrov A, Forth JH, Zani L, Beer M, Blome S. No evidence for long-term carrier status of pigs after African swine fever virus infection. Transbound Emerg Dis 2018; 65:1318-1328. [PMID: 29679458 DOI: 10.1111/tbed.12881] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Indexed: 11/29/2022]
Abstract
This study targeted the assessment of a potential African swine fever virus (ASFV) carrier state of 30 pigs in total which were allowed to recover from infection with ASFV "Netherlands'86" prior exposure to six healthy sentinel pigs for more than 2 months. Throughout the whole trial, blood and swab samples were subjected to routine virological and serological investigations. At the end of the trial, necropsy of all animals was performed and viral persistence and distribution were assessed. Upon infection, a wide range of clinical and pathomorphological signs were observed. After an initial acute phase in all experimentally inoculated pigs, 66.6% recovered completely and seroconverted. However, viral genome was detectable in blood samples for up to 91 days. Lethal outcomes were observed in 33.3% of the pigs with both acute and prolonged courses. No ASFV transmission occurred over the whole in-contact phase from survivors to sentinels. Similarly, infectious ASFV was not detected in any of the tissue samples from ASFV convalescent and in-contact pigs. These findings indicate that the suggested role of ASFV survivors is overestimated and has to be reconsidered thoroughly for future risk assessments.
Collapse
Affiliation(s)
- A Petrov
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Insel Riems, Germany
| | - J H Forth
- Institute of Infectology, Friedrich-Loeffler-Institut, Insel Riems, Germany
| | - L Zani
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Insel Riems, Germany
| | - M Beer
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Insel Riems, Germany
| | - S Blome
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Insel Riems, Germany
| |
Collapse
|
38
|
C G, I N, A S, V D, A S, E M, C P, R N, M A. Evolution in Europe of African swine fever genotype II viruses from highly to moderately virulent. Vet Microbiol 2018; 219:70-79. [PMID: 29778207 DOI: 10.1016/j.vetmic.2018.04.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/01/2018] [Accepted: 04/02/2018] [Indexed: 10/17/2022]
Abstract
Since its arrival in the Caucasus and Russia in 2007, African swine fever virus (ASFV) has spread widely and has now affected the EU countries of Estonia, Latvia, Lithuania, Poland and, more recently, the Czech Republic and Romania. The ever-increasing evidence of seropositive wild boar in certain areas suggests that some animals may be surviving for some time or could even be recovering from the disease. This could be due to acquired immunity after the primary infection and/or the presence of related viruses of reduced virulence. To assess these hypotheses, two ASFV field strains from Estonia were studied in vivo in two groups of domestic pigs. After an incubation period of 4 ± 1.6 days, the pigs inoculated intramuscularly with Es15/WB-Tartu 14 ASFV (group 2) developed clinical signs associated with acute disease and succumbed 7 and 11 days post infection (dpi). Pigs inoculated with Es15/WB-Valga-14 ASFV (group 1) had longer incubation times (8 days) than those in group 2 and developed variable clinical signs and lesions compatible with subacute and chronic forms of ASF; they succumbed at 11 and 25 dpi. The in-contact pigs in both groups became infected 7-14 days after exposure and exhibited variable clinical manifestations and pathological findings ranging from acute to chronic disease. Two animals per group recovered completely after infection and were protected against a subsequent homologous virus challenge-exposure performed at 78 dpi. Under experimental conditions, no transmission occurred from the survivors to susceptible sentinel pigs housed together with the survivors 137 days after the primary infection.
Collapse
Affiliation(s)
- Gallardo C
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain.
| | - Nurmoja I
- Estonian NRL: Estonian Veterinary and Food Laboratory, Kreutzwaldi 30, Tartu, 51006, Estonia
| | - Soler A
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Delicado V
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Simón A
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Martin E
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Perez C
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Nieto R
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| | - Arias M
- European Union Reference Laboratory for African Swine Fever (EURL), Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130, Madrid, Spain
| |
Collapse
|
39
|
Guinat C, Porphyre T, Gogin A, Dixon L, Pfeiffer DU, Gubbins S. Inferring within-herd transmission parameters for African swine fever virus using mortality data from outbreaks in the Russian Federation. Transbound Emerg Dis 2018; 65:e264-e271. [PMID: 29120101 PMCID: PMC5887875 DOI: 10.1111/tbed.12748] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Indexed: 11/28/2022]
Abstract
Mortality data are routinely collected for many livestock and poultry species, and they are often used for epidemiological purposes, including estimating transmission parameters. In this study, we infer transmission rates for African swine fever virus (ASFV), an important transboundary disease of swine, using mortality data collected from nine pig herds in the Russian Federation with confirmed outbreaks of ASFV. Parameters in a stochastic model for the transmission of ASFV within a herd were estimated using approximate Bayesian computation. Estimates for the basic reproduction number varied amongst herds, ranging from 4.4 to 17.3. This was primarily a consequence of differences in transmission rate (range: 0.7-2.2), but also differences in the mean infectious period (range: 4.5-8.3 days). We also found differences amongst herds in the mean latent period (range: 5.8-9.7 days). Furthermore, our results suggest that ASFV could be circulating in a herd for several weeks before a substantial increase in mortality is observed in a herd, limiting the usefulness of mortality data as a means of early detection of an outbreak. However, our results also show that mortality data are a potential source of data from which to infer transmission parameters, at least for diseases which cause high mortality.
Collapse
Affiliation(s)
- C Guinat
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, Hatfield, Hertfordshire, UK.,The Pirbright Institute, Pirbright, Surrey, UK
| | - T Porphyre
- The Roslin Institute, University of Edinburgh, Roslin, Midlothian, UK
| | - A Gogin
- European Food Safety Authority, Parma, Italy.,Federal Research Center for Virology and Microbiology, Pokrov, Russia
| | - L Dixon
- The Pirbright Institute, Pirbright, Surrey, UK
| | - D U Pfeiffer
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, Hatfield, Hertfordshire, UK.,College of Veterinary Medicine & Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - S Gubbins
- The Pirbright Institute, Pirbright, Surrey, UK
| |
Collapse
|
40
|
Bayesian inference of epidemiological parameters from transmission experiments. Sci Rep 2017; 7:16774. [PMID: 29196741 PMCID: PMC5711876 DOI: 10.1038/s41598-017-17174-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 11/21/2017] [Indexed: 01/18/2023] Open
Abstract
Epidemiological parameters for livestock diseases are often inferred from transmission experiments. However, there are several limitations inherent to the design of such experiments that limits the precision of parameter estimates. In particular, infection times and latent periods cannot be directly observed and infectious periods may also be censored. We present a Bayesian framework accounting for these features directly and employ Markov chain Monte Carlo techniques to provide robust inferences and quantify the uncertainty in our estimates. We describe the transmission dynamics using a susceptible-exposed-infectious-removed compartmental model, with gamma-distributed transition times. We then fit the model to published data from transmission experiments for foot-and-mouth disease virus (FMDV) and African swine fever virus (ASFV). Where the previous analyses of these data made various assumptions on the unobserved processes in order to draw inferences, our Bayesian approach includes the unobserved infection times and latent periods and quantifies them along with all other model parameters. Drawing inferences about infection times helps identify who infected whom and can also provide insights into transmission mechanisms. Furthermore, we are able to use our models to measure the difference between the latent periods of inoculated and contact-challenged animals and to quantify the effect vaccination has on transmission.
Collapse
|
41
|
Schulz K, Staubach C, Blome S. African and classical swine fever: similarities, differences and epidemiological consequences. Vet Res 2017; 48:84. [PMID: 29183365 PMCID: PMC5706370 DOI: 10.1186/s13567-017-0490-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 11/08/2017] [Indexed: 11/19/2022] Open
Abstract
For the global pig industry, classical (CSF) and African swine fever (ASF) outbreaks are a constantly feared threat. Except for Sardinia, ASF was eradicated in Europe in the late 1990s, which led to a research focus on CSF because this disease continued to be present. However, ASF remerged in eastern Europe in 2007 and the interest in the disease, its control and epidemiology increased tremendously. The similar names and the same susceptible species suggest a similarity of the two viral diseases, a related biological behaviour and, correspondingly, similar epidemiological features. However, there are several essential differences between both diseases, which need to be considered for the design of control or preventive measures. In the present review, we aimed to collate differences and similarities of the two diseases that impact epidemiology and thus the necessary control actions. Our objective was to discuss critically, if and to which extent the current knowledge can be transferred from one disease to the other and where new findings should lead to a critical review of measures relating to the prevention, control and surveillance of ASF and CSF. Another intention was to identify research gaps, which need to be closed to increase the chances of a successful eradication of ASF and therefore for a decrease of the economic threat for pig holdings and the international trade.
Collapse
Affiliation(s)
- Katja Schulz
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald, Insel Riems Germany
| | - Christoph Staubach
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493 Greifswald, Insel Riems Germany
| | - Sandra Blome
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Diagnostic Virology, Südufer 10, 17493 Greifswald, Insel Riems Germany
| |
Collapse
|
42
|
Abstract
African swine fever (ASF) is an acute and often fatal disease affecting domestic pigs and wild boar, with severe economic consequences for affected countries. ASF is endemic in sub-Saharan Africa and the island of Sardinia, Italy. Since 2007, the virus emerged in the republic of Georgia, and since then spread throughout the Caucasus region and Russia. Outbreaks have also been reported in Belarus, Ukraine, Lithuania, Latvia, Estonia, Romania, Moldova, Czech Republic, and Poland, threatening neighboring West European countries. The causative agent, the African swine fever virus (ASFV), is a large, enveloped, double-stranded DNA virus that enters the cell by macropinocytosis and a clathrin-dependent mechanism. African Swine Fever Virus is able to interfere with various cellular signaling pathways resulting in immunomodulation, thus making the development of an efficacious vaccine very challenging. Inactivated preparations of African Swine Fever Virus do not confer protection, and the role of antibodies in protection remains unclear. The use of live-attenuated vaccines, although rendering suitable levels of protection, presents difficulties due to safety and side effects in the vaccinated animals. Several African Swine Fever Virus proteins have been reported to induce neutralizing antibodies in immunized pigs, and vaccination strategies based on DNA vaccines and recombinant proteins have also been explored, however, without being very successful. The complexity of the virus particle and the ability of the virus to modulate host immune responses are most likely the reason for this failure. Furthermore, no permanent cell lines able to sustain productive virus infection by both virulent and naturally attenuated African Swine Fever Virus strains exist so far, thus impairing basic research and the commercial production of attenuated vaccine candidates.
Collapse
|
43
|
Arias M, de la Torre A, Dixon L, Gallardo C, Jori F, Laddomada A, Martins C, Parkhouse RM, Revilla Y, Rodriguez F, Sanchez-Vizcaino JM. Approaches and Perspectives for Development of African Swine Fever Virus Vaccines. Vaccines (Basel) 2017; 5:vaccines5040035. [PMID: 28991171 PMCID: PMC5748602 DOI: 10.3390/vaccines5040035] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/01/2017] [Accepted: 10/03/2017] [Indexed: 12/25/2022] Open
Abstract
African swine fever (ASF) is a complex disease of swine, caused by a large DNA virus belonging to the family Asfarviridae. The disease shows variable clinical signs, with high case fatality rates, up to 100%, in the acute forms. ASF is currently present in Africa and Europe where it circulates in different scenarios causing a high socio-economic impact. In most affected regions, control has not been effective in part due to lack of a vaccine. The availability of an effective and safe ASFV vaccines would support and enforce control-eradication strategies. Therefore, work leading to the rational development of protective ASF vaccines is a high priority. Several factors have hindered vaccine development, including the complexity of the ASF virus particle and the large number of proteins encoded by its genome. Many of these virus proteins inhibit the host's immune system thus facilitating virus replication and persistence. We review previous work aimed at understanding ASFV-host interactions, including mechanisms of protective immunity, and approaches for vaccine development. These include live attenuated vaccines, and "subunit" vaccines, based on DNA, proteins, or virus vectors. In the shorter to medium term, live attenuated vaccines are the most promising and best positioned candidates. Gaps and future research directions are evaluated.
Collapse
Affiliation(s)
- Marisa Arias
- European Union Reference Laboratory for ASF, Centro de Investigación en Sanidad Animal (INIA-CISA), 28015 Madrid, Spain; (A.D.L.T.); (C.G.)
- Correspondence: ; Tel.: +34-916-202-300
| | - Ana de la Torre
- European Union Reference Laboratory for ASF, Centro de Investigación en Sanidad Animal (INIA-CISA), 28015 Madrid, Spain; (A.D.L.T.); (C.G.)
| | - Linda Dixon
- The Pirbright Institute (TPI), Surrey GU24 0NF, UK;
| | - Carmina Gallardo
- European Union Reference Laboratory for ASF, Centro de Investigación en Sanidad Animal (INIA-CISA), 28015 Madrid, Spain; (A.D.L.T.); (C.G.)
| | - Ferran Jori
- ASTRE, University of Montpellier, CIRAD, INRA, F-34398 Montpellier, France
| | - Alberto Laddomada
- Istituto Zooprofilattico Sperimentale della Sardegna (IZS-Sardegna), 07100 Sassari, Sardinia, Italy;
| | - Carlos Martins
- Faculdade de Medicina Veterinária (FMV-ULisboa), 1300-477 Lisbon, Portugal;
| | - R. Michael Parkhouse
- Instituto Gulbenkian de Ciência (IGC), Rua Quinta Grande 6, 2780-156 Oeiras, Portugal;
| | - Yolanda Revilla
- Centro de Biología Molecular Severo Ochoa (CBMSO-CSIC-UAM), C/ Nicolás Cabrera nº 1, Campus de Cantoblanco, 28049 Madrid, Spain;
| | - Fernando Rodriguez
- Institute for Research and Technology Food and Agriculture (IRTA), Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain;
| | - Jose-Manuel Sanchez-Vizcaino
- OIE Reference Laboratory for ASF, Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Universidad Complutense de Madrid, Avda. Puerta del Hierro, 28040 Madrid, Spain;
| |
Collapse
|
44
|
Herrera-Ibatá DM, Martínez-López B, Quijada D, Burton K, Mur L. Quantitative approach for the risk assessment of African swine fever and Classical swine fever introduction into the United States through legal imports of pigs and swine products. PLoS One 2017; 12:e0182850. [PMID: 28797058 PMCID: PMC5552331 DOI: 10.1371/journal.pone.0182850] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 07/25/2017] [Indexed: 11/18/2022] Open
Abstract
The US livestock safety strongly depends on its capacity to prevent the introduction of Transboundary Animal Diseases (TADs). Therefore, accurate and updated information on the location and origin of those potential TADs risks is essential, so preventive measures as market restrictions can be put on place. The objective of the present study was to evaluate the current risk of African swine fever (ASF) and Classical swine fever (CSF) introduction into the US through the legal importations of live pigs and swine products using a quantitative approach that could be later applied to other risks. Four quantitative stochastic risk assessment models were developed to estimate the monthly probabilities of ASF and CSF release into the US, and the exposure of susceptible populations (domestic and feral swine) to these introductions at state level. The results suggest a low annual probability of either ASF or CSF introduction into the US, by any of the analyzed pathways (5.5*10-3). Being the probability of introduction through legal imports of live pigs (1.8*10-3 for ASF, and 2.5*10-3 for CSF) higher than the risk of legally imported swine products (8.90*10-4 for ASF, and 1.56*10-3 for CSF). This could be caused due to the low probability of exposure associated with this type of commodity (products). The risk of feral pigs accessing to swine products discarded in landfills was slightly higher than the potential exposure of domestic pigs through swill feeding. The identification of the months at highest risk, the origin of the higher risk imports, and the location of the US states most vulnerable to those introductions (Iowa, Minnesota and Wisconsin for live swine and California, Florida and Texas for swine products), is valuable information that would help to design prevention, risk-mitigation and early-detection strategies that would help to minimize the catastrophic consequences of potential ASF/CSF introductions into the US.
Collapse
Affiliation(s)
- Diana María Herrera-Ibatá
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, United States of America
| | - Beatriz Martínez-López
- Center for Animal Disease Modelling and Surveillance (CADMS), University of California Davis, Davis, CA, United States of America
| | - Darla Quijada
- National Agricultural Biosecurity Center, Kansas State University, Manhattan, KS, United States of America
| | - Kenneth Burton
- National Agricultural Biosecurity Center, Kansas State University, Manhattan, KS, United States of America
| | - Lina Mur
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, United States of America
- * E-mail:
| |
Collapse
|
45
|
Estimation of the transmission dynamics of African swine fever virus within a swine house. Epidemiol Infect 2017; 145:2787-2796. [DOI: 10.1017/s0950268817001613] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
SUMMARYThe spread of African swine fever virus (ASFV) threatens to reach further parts of Europe. In countries with a large swine production, an outbreak of ASF may result in devastating economic consequences for the swine industry. Simulation models can assist decision makers setting up contingency plans. This creates a need for estimation of parameters. This study presents a new analysis of a previously published study. A full likelihood framework is presented including the impact of model assumptions on the estimated transmission parameters. As animals were only tested every other day, an interpretation was introduced to cover the weighted infectiousness on unobserved days for the individual animals (WIU). Based on our model and the set of assumptions, the within- and between-pen transmission parameters were estimated to βw = 1·05 (95% CI 0·62–1·72), βb = 0·46 (95% CI 0·17–1·00), respectively, and the WIU = 1·00 (95% CI 0–1). Furthermore, we simulated the spread of ASFV within a pig house using a modified SEIR-model to establish the time from infection of one animal until ASFV is detected in the herd. Based on a chosen detection limit of 2·55% equivalent to 10 dead pigs out of 360, the disease would be detected 13–19 days after introduction.
Collapse
|
46
|
Titov I, Burmakina G, Morgunov Y, Morgunov S, Koltsov A, Malogolovkin A, Kolbasov D. Virulent strain of African swine fever virus eclipses its attenuated derivative after challenge. Arch Virol 2017; 162:3081-3088. [PMID: 28691128 DOI: 10.1007/s00705-017-3471-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 06/01/2017] [Indexed: 11/28/2022]
Abstract
African swine fever (ASF) is one of the most devastating diseases affecting the swine industry worldwide. No effective vaccine is currently available for disease prevention and control. Although live attenuated vaccines (LAV) have demonstrated great potential for immunizing against homologous strains of African swine fever virus (ASFV), adverse reactions from LAV remain a concern. Here, by using a homologous ASFV Congo strain system, we show passage-attenuated Congo LAV to induce an efficient protective immune response against challenge with the virulent parental Congo strain. Notably, only the parental challenge Congo strain was identified in blood and organs of recovered pigs through B602L gene PCR, long-range PCR, nucleotide sequencing and virus isolation. Thus, despite the great protective potential of homologous attenuated ASFV strain, the challenge Congo strain can persist for weeks in recovered pigs and a recrudescence of virulent virus at late time post-challenge may occur.
Collapse
Affiliation(s)
- Ilya Titov
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| | - Galina Burmakina
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| | - Yuriy Morgunov
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| | - Sergey Morgunov
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| | - Andrey Koltsov
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| | - Alexander Malogolovkin
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia.
| | - Denis Kolbasov
- Molecular Virology Laboratory, National Research Institute of Veterinary Virology and Microbiology, Volginsky, Academician Bakoulova Street, bldg. 1, Petushki, Vladimir, 601125, Russia
| |
Collapse
|
47
|
Mur L, Sánchez-Vizcaíno JM, Fernández-Carrión E, Jurado C, Rolesu S, Feliziani F, Laddomada A, Martínez-López B. Understanding African Swine Fever infection dynamics in Sardinia using a spatially explicit transmission model in domestic pig farms. Transbound Emerg Dis 2017; 65:123-134. [PMID: 28296281 DOI: 10.1111/tbed.12636] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Indexed: 01/08/2023]
Abstract
African swine fever virus (ASFV) has been endemic in Sardinia since 1978, resulting in severe losses for local pig producers and creating important problems for the island's veterinary authorities. This study used a spatially explicit stochastic transmission model followed by two regression models to investigate the dynamics of ASFV spread amongst domestic pig farms, to identify geographic areas at highest risk and determine the role of different susceptible pig populations (registered domestic pigs, non-registered domestic pigs [brado] and wild boar) in ASF occurrence. We simulated transmission within and between farms using an adapted version of the previously described model known as Be-FAST. Results from the model revealed a generally low diffusion of ASF in Sardinia, with only 24% of the simulations resulting in disease spread, and for each simulated outbreak on average only four farms and 66 pigs were affected. Overall, local spread (indirect transmission between farms within a 2 km radius through fomites) was the most common route of transmission, being responsible for 98.6% of secondary cases. The risk of ASF occurrence for each domestic pig farm was estimated from the spread model results and integrated in two regression models together with available data for brado and wild boar populations. There was a significant association between the density of all three populations (domestic pigs, brado, and wild boar) and ASF occurrence in Sardinia. The most significant risk factors were the high densities of brado (OR = 2.2) and wild boar (OR = 2.1). The results of both analyses demonstrated that ASF epidemiology and infection dynamics in Sardinia create a complex and multifactorial disease situation, where all susceptible populations play an important role. To stop ASF transmission in Sardinia, three main factors (improving biosecurity on domestic pig farms, eliminating brado practices and better management of wild boars) need to be addressed.
Collapse
Affiliation(s)
- L Mur
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - J M Sánchez-Vizcaíno
- VISAVET Center and Animal Health Department, Veterinary School, Complutense University of Madrid, Madrid, Spain
| | - E Fernández-Carrión
- VISAVET Center and Animal Health Department, Veterinary School, Complutense University of Madrid, Madrid, Spain
| | - C Jurado
- VISAVET Center and Animal Health Department, Veterinary School, Complutense University of Madrid, Madrid, Spain
| | - S Rolesu
- IZS della Sardegna, Centro di Sorveglianza Epidemiologica, Cagliari, Italy
| | | | - A Laddomada
- IZS della Sardegna, Centro di Sorveglianza Epidemiologica, Cagliari, Italy
| | - B Martínez-López
- Center for Animal Disease Modeling and Surveillance (CADMS), University of California Davis, Davis, CA, USA
| |
Collapse
|
48
|
Korennoy FI, Gulenkin VM, Gogin AE, Vergne T, Karaulov AK. Estimating the Basic Reproductive Number for African Swine Fever Using the Ukrainian Historical Epidemic of 1977. Transbound Emerg Dis 2016; 64:1858-1866. [PMID: 27667658 DOI: 10.1111/tbed.12583] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Indexed: 11/30/2022]
Abstract
In 1977, Ukraine experienced a local epidemic of African swine fever (ASF) in the Odessa region. A total of 20 settlements were affected during the course of the epidemic, including both large farms and backyard households. Thanks to timely interventions, the virus circulation was successfully eradicated within 6 months, leading to no additional outbreaks. Detailed report of the outbreak's investigation has been publically available from 2014. The report contains some quantitative data that allow studying the ASF-spread dynamics in the course of the epidemic. In our study, we used this historical epidemic to estimate the basic reproductive number of the ASF virus both within and between farms. The basic reproductive number (R0 ) represents the average number of secondary infections caused by one infectious unit during its infectious period in a susceptible population. Calculations were made under assumption of an exponential initial growth by fitting the approximating curve to the initial segments of the epidemic curves. The R0 both within farm and between farms was estimated at 7.46 (95% confidence interval: 5.68-9.21) and 1.65 (1.42-1.88), respectively. Corresponding daily transmission rates were estimated at 1.07 (0.81-1.32) and 0.09 (0.07-0.10). These estimations based on historical data are consistent with those using data generated by the recent epidemic currently affecting eastern Europe. Such results contribute to the published knowledge on the ASF transmission dynamics under natural conditions and could be used to model and predict the spread of ASF in affected and non-affected regions and to evaluate the effectiveness of different control measures.
Collapse
Affiliation(s)
- F I Korennoy
- Federal Center for Animal Health (FGBI ARRIAH), Vladimir, Russia
| | - V M Gulenkin
- Federal Center for Animal Health (FGBI ARRIAH), Vladimir, Russia
| | - A E Gogin
- National Research Institute for Veterinary Virology and Microbiology of Russia (SSINRRIVV&M), Pokrov, Russia
| | - T Vergne
- Royal Veterinary College, University of London, London, UK
| | - A K Karaulov
- Federal Center for Animal Health (FGBI ARRIAH), Vladimir, Russia
| |
Collapse
|
49
|
Barongo MB, Bishop RP, Fèvre EM, Knobel DL, Ssematimba A. A Mathematical Model that Simulates Control Options for African Swine Fever Virus (ASFV). PLoS One 2016; 11:e0158658. [PMID: 27391689 PMCID: PMC4938631 DOI: 10.1371/journal.pone.0158658] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/20/2016] [Indexed: 01/27/2023] Open
Abstract
A stochastic model designed to simulate transmission dynamics of African swine fever virus (ASFV) in a free-ranging pig population under various intervention scenarios is presented. The model was used to assess the relative impact of the timing of the implementation of different control strategies on disease-related mortality. The implementation of biosecurity measures was simulated through incorporation of a decay function on the transmission rate. The model predicts that biosecurity measures implemented within 14 days of the onset of an epidemic can avert up to 74% of pig deaths due to ASF while hypothetical vaccines that confer 70% immunity when deployed prior to day 14 of the epidemic could avert 65% of pig deaths. When the two control measures are combined, the model predicts that 91% of the pigs that would have otherwise succumbed to the disease if no intervention was implemented would be saved. However, if the combined interventions are delayed (defined as implementation from > 60 days) only 30% of ASF-related deaths would be averted. In the absence of vaccines against ASF, we recommend early implementation of enhanced biosecurity measures. Active surveillance and use of pen-side diagnostic assays, preferably linked to rapid dissemination of this data to veterinary authorities through mobile phone technology platforms are essential for rapid detection and confirmation of ASF outbreaks. This prediction, although it may seem intuitive, rationally confirms the importance of early intervention in managing ASF epidemics. The modelling approach is particularly valuable in that it determines an optimal timing for implementation of interventions in controlling ASF outbreaks.
Collapse
Affiliation(s)
- Mike B. Barongo
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
| | - Richard P Bishop
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
| | - Eric M Fèvre
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
- Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, CH64 7TE, United Kingdom
| | - Darryn L Knobel
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Amos Ssematimba
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
- Department of Mathematics, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda
| |
Collapse
|
50
|
Guinat C, Gogin A, Blome S, Keil G, Pollin R, Pfeiffer DU, Dixon L. Transmission routes of African swine fever virus to domestic pigs: current knowledge and future research directions. Vet Rec 2016; 178:262-7. [PMID: 26966305 PMCID: PMC4819659 DOI: 10.1136/vr.103593] [Citation(s) in RCA: 191] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
African swine fever (ASF) is a major threat to the pig industry in Europe. Since 2007, ASF outbreaks have been ongoing in the Caucasus, Eastern Europe and the Baltic countries, causing severe economic losses for many pig farmers and pork producers. In addition, the number of ASF cases in wild boar populations has dramatically increased over the past few years. Evidence supports direct contact with infectious domestic pigs and wild boars, and consumption of contaminated feed, as the main transmission routes of ASF virus (ASFV) to domestic pigs. However, significant knowledge gaps highlight the urgent need for research to investigate the dynamics of indirect transmission via the environment, the minimal infective doses for contaminated feed ingestion, the probability of effective contacts between infectious wild boars and domestic pigs, the potential for recovered animals to become carriers and a reservoir for transmission, the potential virus persistence within wild boar populations and the influence of human behaviour for the spread of ASFV. This will provide an improved scientific basis to optimise current interventions and develop new tools and strategies to reduce the risk of ASFV transmission to domestic pigs.
Collapse
Affiliation(s)
- Claire Guinat
- Royal Veterinary College, Veterinary Epidemiology, Economics and Public Health Group, Hawkshead Lane, Hatfield, Hertfordshire AL9 7TA, UK
| | - Andrey Gogin
- European Food Safety Authority, Via Carlo Magno 1A, 43126 Parma, Italy
| | - Sandra Blome
- Friedrich-Loeffler Institut, Sudufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Guenther Keil
- Friedrich-Loeffler Institut, Sudufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Reiko Pollin
- Friedrich-Loeffler Institut, Sudufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Dirk U Pfeiffer
- Royal Veterinary College, Veterinary Epidemiology, Economics and Public Health Group, Hawkshead Lane, Hatfield, Hertfordshire AL9 7TA, UK
| | - Linda Dixon
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK
| |
Collapse
|