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Langhorne C, Horsman S, Wood C, Clark R, Price R, Henning J, Grewar JD, Wood BJ, Ranjbar S, McGowan MR, Gibson JS. Bacterial culture and susceptibility test results for clinical mastitis samples from Australia's subtropical dairy region. J Dairy Sci 2024; 107:1151-1163. [PMID: 37769942 DOI: 10.3168/jds.2023-23838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023]
Abstract
This study aimed to identify the pathogens isolated from the milk of cows with clinical mastitis in the subtropical region of Australia and to determine the antimicrobial susceptibility of these bacteria. Thirty dairy herds in the subtropical dairy region were asked to submit milk samples for the first 5 cases of clinical mastitis each month for 12 mo. Samples underwent aerobic culture, and isolates were identified via MALDI-TOF mass spectrometry. Antimicrobial susceptibility was determined for Escherichia coli, Enterococcus spp., Streptococcus agalactiae, Streptococcus uberis, Streptococcus dysgalactiae, Staphylococcus aureus, and non-aureus staphylococci and mammaliicocci (NASM). Between March 2021 and July 2022, 1,230 milk samples were collected. A positive culture result was recorded for 812 (66%) of the milk samples; from these samples, 909 isolates were obtained, including 49 isolates where no identification was possible. The remaining samples were classified as having no growth (16.8%) or as being contaminated (17.2%). The most common isolates with a MALDI-TOF diagnosis (n = 909) were Strep. uberis (23.6%), followed by the NASM group (15.0%). Farms enrolled in the study were in 3 distinct locations within the subtropical dairy region: North Queensland, Southeast Queensland, and Northern New South Wales. Some variation in isolate prevalence occurred between these 3 locations. We found lower odds of a sample being positive for E. coli in North Queensland (odds ratio [OR]: 0.25; 95% confidence interval [CI]: 0.07-0.87) and higher odds in Southeast Queensland (OR: 4.01; 95% CI: 1.96-8.20) compared with the reference, Northern New South Wales. We further found higher odds of Strep. dysgalactiae in North Queensland (OR: 5.69; 95% CI: 1.85-17.54) and Southeast Queensland compared with Northern New South Wales (OR: 3.99; 95% CI: 1.73-9.22). Although some seasonal patterns were observed, season was not significant for any of the analyzed isolates. Farm-level differences in pathogen profiles were obvious. Overall, clinical mastitis pathogens had low levels of resistance to the antimicrobials tested. This research demonstrates that Strep. uberis and the NASM bacterial group are the most common pathogens causing clinical mastitis in the subtropical dairy region. It highlights the importance of understanding pathogenic causes of mastitis at the farm and regional level for targeted control and therapy.
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Affiliation(s)
- Charlotte Langhorne
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia.
| | - Sara Horsman
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Caitlin Wood
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Rachael Clark
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Rochelle Price
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Joerg Henning
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | | | - Benjamin J Wood
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Shahab Ranjbar
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Michael R McGowan
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
| | - Justine S Gibson
- School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia
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Schulman ML, Hayes NK, Wilson TA, Grewar JD. Immunocontraceptive Efficacy of Native Porcine Zona Pellucida (pZP) Treatment of Nevada's Virginia Range Free-Roaming Horse Population. Vaccines (Basel) 2024; 12:96. [PMID: 38250909 PMCID: PMC10820100 DOI: 10.3390/vaccines12010096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/07/2024] [Accepted: 01/16/2024] [Indexed: 01/23/2024] Open
Abstract
In North America, range constraints due to burgeoning development increasingly encroach on wild horse habitat and necessitate effective but humane reproductive management. The largest free-roaming wild horse fertility control program by population (>3500) and territory size (≈300,000 acres) is located within Nevada's Virginia Range. Data from a field study investigated porcine zona pellucida (pZP) immunocontraception via remote dart delivery to mares in this population. Analyses aimed to measure efficacy by treatment effects on annual birth rates and population demographics and to evaluate treatment frequency and season against these variables. Analyses included mares' monthly data (January 2019-December 2022; 48 months), characterized by cumulative vaccination numbers subset into four classifications considering the vaccine as having no loss of efficacy or a loss within a 6-, 12-, and 18-month period post vaccination; from foaling data, the likelihood of being in foal and of conceiving in that month; and from age, as mature or immature (<1 years-old). A downward foaling rate and trend in the numbers of mature mares, descriptively presented at monthly intervals, showed markedly declining annual seasonal breeding peaks, with no observed change in foaling season or duration. Within four years, population coverage surpassed 70% and was associated with a 58% reduction in foaling, with only a 10% conception rate. Vaccinated mares increased proportionally: assuming a 12-month decay rate, the system reached stability at an average ≈1.0 vaccination/mare/year, providing a robust recommendation for treatment frequency contributing to best management practices.
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Affiliation(s)
- Martin L. Schulman
- Veterinary Population Management Laboratory, Faculty of Veterinary Science, University of Pretoria, Pretoria 0110, South Africa;
| | - Nicole K. Hayes
- American Wild Horse Campaign, Davis, CA 95617, USA; (N.K.H.); (T.A.W.)
| | - Tracy A. Wilson
- American Wild Horse Campaign, Davis, CA 95617, USA; (N.K.H.); (T.A.W.)
| | - John D. Grewar
- Veterinary Population Management Laboratory, Faculty of Veterinary Science, University of Pretoria, Pretoria 0110, South Africa;
- JDATA, Sandbaai 7200, South Africa
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de Klerk JN, Gorsich EE, Grewar JD, Atkins BD, Tennant WSD, Labuschagne K, Tildesley MJ. Modelling African horse sickness emergence and transmission in the South African control area using a deterministic metapopulation approach. PLoS Comput Biol 2023; 19:e1011448. [PMID: 37672554 PMCID: PMC10506717 DOI: 10.1371/journal.pcbi.1011448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 09/18/2023] [Accepted: 08/18/2023] [Indexed: 09/08/2023] Open
Abstract
African horse sickness is an equine orbivirus transmitted by Culicoides Latreille biting midges. In the last 80 years, it has caused several devastating outbreaks in the equine population in Europe, the Far and Middle East, North Africa, South-East Asia, and sub-Saharan Africa. The disease is endemic in South Africa; however, a unique control area has been set up in the Western Cape where increased surveillance and control measures have been put in place. A deterministic metapopulation model was developed to explore if an outbreak might occur, and how it might develop, if a latently infected horse was to be imported into the control area, by varying the geographical location and months of import. To do this, a previously published ordinary differential equation model was developed with a metapopulation approach and included a vaccinated horse population. Outbreak length, time to peak infection, number of infected horses at the peak, number of horses overall affected (recovered or dead), re-emergence, and Rv (the basic reproduction number in the presence of vaccination) were recorded and displayed using GIS mapping. The model predictions were compared to previous outbreak data to ensure validity. The warmer months (November to March) had longer outbreaks than the colder months (May to September), took more time to reach the peak, and had a greater total outbreak size with more horses infected at the peak. Rv appeared to be a poor predictor of outbreak dynamics for this simulation. A sensitivity analysis indicated that control measures such as vaccination and vector control are potentially effective to manage the spread of an outbreak, and shortening the vaccination window to July to September may reduce the risk of vaccine-associated outbreaks.
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Affiliation(s)
- Joanna N. de Klerk
- The Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Erin E. Gorsich
- The Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - John D. Grewar
- South African Equine Health and Protocols NPC, Baker Square, Paardevlei, Cape Town, South Africa
| | - Benjamin D. Atkins
- The Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Warren S. D. Tennant
- The Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Karien Labuschagne
- Epidemiology, Parasites and Vectors, Agricultural Research Council, Onderstepoort Veterinary Research, Onderstepoort, South Africa
| | - Michael J. Tildesley
- The Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, School of Life Sciences and Mathematics Institute, University of Warwick, Coventry, United Kingdom
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Annand EJ, Horsburgh BA, Xu K, Reid PA, Poole B, de Kantzow MC, Brown N, Tweedie A, Michie M, Grewar JD, Jackson AE, Singanallur NB, Plain KM, Kim K, Tachedjian M, van der Heide B, Crameri S, Williams DT, Secombe C, Laing ED, Sterling S, Yan L, Jackson L, Jones C, Plowright RK, Peel AJ, Breed AC, Diallo I, Dhand NK, Britton PN, Broder CC, Smith I, Eden JS. Novel Hendra Virus Variant Detected by Sentinel Surveillance of Horses in Australia. Emerg Infect Dis 2022; 28:693-704. [PMID: 35202527 PMCID: PMC8888208 DOI: 10.3201/eid2803.211245] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We identified and isolated a novel Hendra virus (HeV) variant not detected by routine testing from a horse in Queensland, Australia, that died from acute illness with signs consistent with HeV infection. Using whole-genome sequencing and phylogenetic analysis, we determined the variant had ≈83% nt identity with prototypic HeV. In silico and in vitro comparisons of the receptor-binding protein with prototypic HeV support that the human monoclonal antibody m102.4 used for postexposure prophylaxis and current equine vaccine will be effective against this variant. An updated quantitative PCR developed for routine surveillance resulted in subsequent case detection. Genetic sequence consistency with virus detected in grey-headed flying foxes suggests the variant circulates at least among this species. Studies are needed to determine infection kinetics, pathogenicity, reservoir-species associations, viral-host coevolution, and spillover dynamics for this virus. Surveillance and biosecurity practices should be updated to acknowledge HeV spillover risk across all regions frequented by flying foxes.
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Grewar JD, Kotze JL, Parker BJ, van Helden LS, Weyer CT. An entry risk assessment of African horse sickness virus into the controlled area of South Africa through the legal movement of equids. PLoS One 2021; 16:e0252117. [PMID: 34038466 PMCID: PMC8153453 DOI: 10.1371/journal.pone.0252117] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/10/2021] [Indexed: 11/19/2022] Open
Abstract
South Africa is endemic for African horse sickness (AHS), an important health and trade-sensitive disease of equids. The country is zoned with movement control measures facilitating an AHS-free controlled area in the south-west. Our objective was to quantitatively establish the risk of entry of AHS virus into the AHS controlled area through the legal movement of horses. Outcomes were subcategorised to evaluate movement pathway, temporal, and spatial differences in risk. A 'no-control' scenario allowed for evaluation of the impact of control measures. Using 2019 movement and AHS case data, and country-wide census data, a stochastic model was developed establishing local municipality level entry risk of AHSV at monthly intervals. These were aggregated to annual probability of entry. Sensitivity analysis evaluated model variables on their impact on the conditional means of the probability of entry. The median monthly probability of entry of AHSV into the controlled area of South Africa ranged from 0.75% (June) to 5.73% (February), with the annual median probability of entry estimated at 20.21% (95% CI: 15.89%-28.89%). The annual risk of AHSV entry compared well with the annual probability of introduction of AHS into the controlled area, which is ~10% based on the last 20 years of outbreak data. Direct non-quarantine movements made up most movements and accounted for most of the risk of entry. Spatial analysis showed that, even though reported case totals were zero throughout 2019 in the Western Cape, horses originating from this province still pose a risk that should not be ignored. Control measures decrease risk by a factor of 2.8 on an annual basis. Not only do the outcomes of this study inform domestic control, they can also be used for scientifically justified trade decision making, since in-country movement control forms a key component of export protocols.
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Affiliation(s)
- John D. Grewar
- Department of Production Animal Studies, University of Pretoria, Pretoria, Gauteng, South Africa
- South African Equine Health and Protocols NPC, Cape Town, Western Cape Province, South Africa
- * E-mail:
| | - Johann L. Kotze
- Department of Production Animal Studies, University of Pretoria, Pretoria, Gauteng, South Africa
| | - Beverly J. Parker
- South African Equine Health and Protocols NPC, Cape Town, Western Cape Province, South Africa
| | - Lesley S. van Helden
- Veterinary Services, Western Cape Department of Agriculture, Elsenburg, Western Cape Province, South Africa
| | - Camilla T. Weyer
- South African Equine Health and Protocols NPC, Cape Town, Western Cape Province, South Africa
- Department of Veterinary Tropical Diseases, University of Pretoria, Pretoria, Gauteng, South Africa
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6
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Boden LA, Auty HK, Delgado A, Grewar JD, Hagerman AD, Porphyre T, Russell GC. Editorial: Risk-Based Evidence for Animal Health Policy. Front Vet Sci 2020; 7:595. [PMID: 33088827 PMCID: PMC7498533 DOI: 10.3389/fvets.2020.00595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 07/27/2020] [Indexed: 11/21/2022] Open
Affiliation(s)
- Lisa A Boden
- The Global Academy of Agriculture and Food Security, The Royal (Dick) School of Veterinary Studies, The Roslin Institute, University of Edinburgh, Midlothian, United Kingdom
| | - Harriet K Auty
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Amy Delgado
- United States Department of Agriculture, Animal Plant and Health Inspection Service, Veterinary Services, Strategy and Policy, Center for Epidemiology and Animal Health, Fort Collins, CO, United States
| | - John D Grewar
- South African Equine Health and Protocols NPC, Cape Town, South Africa
| | - Amy D Hagerman
- Department of Agricultural Economics, Oklahoma State University, Stillwater, OK, United States
| | - Thibaud Porphyre
- The Royal (Dick) School of Veterinary Studies, The Roslin Institute, University of Edinburgh, Midlothian, United Kingdom
| | - George C Russell
- Moredun Research Institute, Pentlands Science Park, Midlothian, United Kingdom
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De Klerk JN, Quan M, Grewar JD. Socio-economic impacts of working horses in urban and peri-urban areas of the Cape Flats, South Africa. J S Afr Vet Assoc 2020; 91:e1-e11. [PMID: 32370530 PMCID: PMC7203185 DOI: 10.4102/jsava.v91i0.2009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 12/27/2019] [Accepted: 02/07/2020] [Indexed: 11/21/2022] Open
Abstract
In the Cape Flats townships, Cape Town, South Africa, there are more than 250 working cart horses. They serve the community with scrap metal and garden refuse removal, human transport and the selling of goods. A questionnaire was undertaken to understand the social and economic impacts of a horse and cart in the Cape Flats on individual owners and/or drivers, their households and the community. A mixture of classical quantitative questions combined with qualitative participatory technique questions were used. A total of 100 participants took part in the questionnaire, who cart with 163 horses between them. The majority (89%) identified the cart horse income as their primary income source. Apart from the participants, an additional 716 people were supported financially through this income, where the mean number of children supported was 2.9 (95% confidence interval [CI]: ±0.42) per interviewed participant. Scrap metal transportation was the most common work and the season (winter) had a negative impact on their ability to work. The spatial extent to which a cart horses work was determined and related back to the impact on the horse and participant of the survey. It was demonstrated that the cart horse industry had an impact not only on those who worked in the industry, but also on the surrounding residents, either through their work or through supporting others with their income. This study revealed that the concepts of ‘One Health’ and ‘Health in Social-Ecological Systems’, in action as horse and human health within the Cape Flats are closely intertwined.
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Affiliation(s)
- Joanna N De Klerk
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium; and, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
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Porphyre T, Grewar JD. Assessing the potential of plains zebra to maintain African horse sickness in the Western Cape Province, South Africa. PLoS One 2019; 14:e0222366. [PMID: 31671099 PMCID: PMC6822716 DOI: 10.1371/journal.pone.0222366] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 10/16/2019] [Indexed: 11/18/2022] Open
Abstract
African horse sickness (AHS) is a disease of equids that results in a non-tariff barrier to the trade of live equids from affected countries. AHS is endemic in South Africa except for a controlled area in the Western Cape Province (WCP) where sporadic outbreaks have occurred in the past 2 decades. There is potential that the presence of zebra populations, thought to be the natural reservoir hosts for AHS, in the WCP could maintain AHS virus circulation in the area and act as a year-round source of infection for horses. However, it remains unclear whether the epidemiology or the ecological conditions present in the WCP would enable persistent circulation of AHS in the local zebra populations. Here we developed a hybrid deterministic-stochastic vector-host compartmental model of AHS transmission in plains zebra (Equus quagga), where host populations are age- and sex-structured and for which population and AHS transmission dynamics are modulated by rainfall and temperature conditions. Using this model, we showed that populations of plains zebra present in the WCP are not sufficiently large for AHS introduction events to become endemic and that coastal populations of zebra need to be >2500 individuals for AHS to persist >2 years, even if zebras are infectious for more than 50 days. AHS cannot become endemic in the coastal population of the WCP unless the zebra population involves at least 50,000 individuals. Finally, inland populations of plains zebra in the WCP may represent a risk for AHS to persist but would require populations of at least 500 zebras or show unrealistic duration of infectiousness for AHS introduction events to become endemic. Our results provide evidence that the risk of AHS persistence from a single introduction event in a given plains zebra population in the WCP is extremely low and it is unlikely to represent a long-term source of infection for local horses.
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Affiliation(s)
- Thibaud Porphyre
- The Roslin Institute, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- * E-mail:
| | - John D. Grewar
- South African Equine Health & Protocols NPC, Paardevlei, Cape Town, South Africa
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9
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Miller MA, Davey SC, Van Helden LS, Kettner F, May SM, Last R, Grewar JD, Botha L, Van Helden PD. Paratuberculosis in a domestic dog in South Africa. J S Afr Vet Assoc 2017; 88:e1-e5. [PMID: 28397513 PMCID: PMC6138219 DOI: 10.4102/jsava.v88i0.1441] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 01/24/2017] [Accepted: 01/13/2017] [Indexed: 11/01/2022] Open
Abstract
This case report shows that Mycobacterium avium subsp. paratuberculosis (MAP) infection can cause clinical disease in domestic dogs, and should be considered as a differential diagnosis for gastrointestinal inflammatory conditions. A male dachshund presented with lethargy and pain. Enlarged mesenteric lymph nodes were found on abdominal ultrasound examination. Cytological examination of lymph node aspirates was consistent with granulomatous inflammation, which was culture-confirmed as MAP. Although we were unable to confirm the source of infection, the dog's history included exposure to sheep in the Western Cape.
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Affiliation(s)
- Michele A Miller
- DST NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Stellenbosch University.
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Weyer CT, Grewar JD, Burger P, Joone C, Lourens C, MacLachlan NJ, Guthrie AJ. Dynamics of African horse sickness virus nucleic acid and antibody in horses following immunization with a commercial polyvalent live attenuated vaccine. Vaccine 2017; 35:2504-2510. [PMID: 28341113 DOI: 10.1016/j.vaccine.2017.03.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/24/2017] [Accepted: 03/03/2017] [Indexed: 10/19/2022]
Abstract
African horse sickness (AHS) is a fatal disease of equids relevant to the global equine industry. Detection of AHS virus (AHSV) during outbreaks has become more rapid and efficient with the advent of group specific reverse transcriptase quantitative polymerase chain reaction (GS RT-qPCR) assays to detect AHSV nucleic acid. Use of GS RT-qPCR together with recently described type specific (TS RT-qPCR) assays cannot only expedite diagnosis of AHS but also facilitate further evaluation of the dynamics of AHSV infection in the equine host. A potential limitation to the application of these assays is that they detect viral nucleic acid originating from any AHS live attenuated vaccine (LAV), which is the vaccine type routinely administered to horses in South Africa. The aim of this study was to contrast the dynamics and duration of the RNAaemia to the serological responses of horses following immunization with a commercial polyvalent AHSV-LAV using GS and TS RT-qPCR assays and serum neutralisation tests. The results of the study showed extended RNAemia in vaccinated horses, and that more horses tested positive on GS RT-qPCR with lower Cq values after receiving the AHSV-LAV containing types 1, 3 and 4 prior to the vaccine containing types 2, 6, 7 and 8, rather than when the vaccine combinations were reversed. Furthermore, lower Cq values were obtained when vaccines were administered 4weeks apart as compared with a longer interval or 12weeks apart. These findings are of particular relevance in regions where AHSV-LAVs are used as the use of these vaccines may complicate the accurate interpretation of diagnostic testing results.
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Affiliation(s)
- C T Weyer
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
| | - J D Grewar
- Western Cape Department of Agriculture, Veterinary Services, Elsenburg, South Africa
| | - P Burger
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - C Joone
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - C Lourens
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - N J MacLachlan
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa; Equine Viral Diseases Laboratory, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, United States
| | - A J Guthrie
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
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Weyer CT, Grewar JD, Burger P, Rossouw E, Lourens C, Joone C, le Grange M, Coetzee P, Venter E, Martin DP, MacLachlan NJ, Guthrie AJ. African Horse Sickness Caused by Genome Reassortment and Reversion to Virulence of Live, Attenuated Vaccine Viruses, South Africa, 2004-2014. Emerg Infect Dis 2016; 22:2087-2096. [PMID: 27442883 PMCID: PMC5189153 DOI: 10.3201/eid2212.160718] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Epidemiologic and phylogenetic analyses show repeated outbreaks derived from
vaccine viruses. African horse sickness (AHS) is a hemorrhagic viral fever of horses. It is the
only equine disease for which the World Organization for Animal Health has
introduced specific guidelines for member countries seeking official recognition
of disease-free status. Since 1997, South Africa has maintained an AHS
controlled area; however, sporadic outbreaks of AHS have occurred in this area.
We compared the whole genome sequences of 39 AHS viruses (AHSVs) from field AHS
cases to determine the source of 3 such outbreaks. Our analysis confirmed that
individual outbreaks were caused by virulent revertants of AHSV type 1 live,
attenuated vaccine (LAV) and reassortants with genome segments derived from AHSV
types 1, 3, and 4 from a LAV used in South Africa. These findings show that
despite effective protection of vaccinated horses, polyvalent LAV may,
paradoxically, place susceptible horses at risk for AHS.
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12
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van Helden LS, Sinclair M, Koen P, Grewar JD. Description of an outbreak of highly pathogenic avian influenza in domestic ostriches (Struthio camelus) in South Africa in 2011. Prev Vet Med 2016; 128:6-11. [PMID: 27237385 DOI: 10.1016/j.prevetmed.2016.03.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 03/11/2016] [Accepted: 03/31/2016] [Indexed: 10/22/2022]
Abstract
In 2011, the commercial ostrich production industry of South Africa experienced an outbreak of highly pathogenic avian influenza (HPAI), subtype H5N2. Surveillance using antibody and antigen detection revealed 42 infected farms with a between-farm prevalence in the affected area of 16%. The outbreak was controlled using depopulation of infected farms, resulting in the direct loss of 10% of the country's domestic ostrich population. Various factors in the ostrich production system were observed that could have contributed to the spread of the virus between farms, including the large number of legal movements of ostriches between farms, access of wild birds to ostrich camps and delays in depopulation of infected farms. Negative effects on the ostrich industry and the local economy of the ostrich-producing area were observed as a result of the outbreak and the disease control measures applied. Prevention and control measures applied as a result of avian influenza in South Africa were informed by this large outbreak and the insights into epidemiology of avian influenza in ostriches that it provided, resulting in stricter biosecurity measures required on every registered ostrich farm in the country.
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Affiliation(s)
- L S van Helden
- Western Cape Veterinary Services, Private Bag X1, Elsenburg 7607, South Africa.
| | - M Sinclair
- Western Cape Veterinary Services, Private Bag X1, Elsenburg 7607, South Africa
| | - P Koen
- Western Cape Veterinary Services, Private Bag X1, Elsenburg 7607, South Africa
| | - J D Grewar
- Western Cape Veterinary Services, Private Bag X1, Elsenburg 7607, South Africa
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Sergeant ES, Grewar JD, Weyer CT, Guthrie AJ. Quantitative Risk Assessment for African Horse Sickness in Live Horses Exported from South Africa. PLoS One 2016; 11:e0151757. [PMID: 26986002 PMCID: PMC4795756 DOI: 10.1371/journal.pone.0151757] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 03/03/2016] [Indexed: 11/30/2022] Open
Abstract
African horse sickness (AHS) is a severe, often fatal, arbovirus infection of horses, transmitted by Culicoides spp. midges. AHS occurs in most of sub-Saharan Africa and is a significant impediment to export of live horses from infected countries, such as South Africa. A stochastic risk model was developed to estimate the probability of exporting an undetected AHS-infected horse through a vector protected pre-export quarantine facility, in accordance with OIE recommendations for trade from an infected country. The model also allows for additional risk management measures, including multiple PCR tests prior to and during pre-export quarantine and optionally during post-arrival quarantine, as well as for comparison of risk associated with exports from a demonstrated low-risk area for AHS and an area where AHS is endemic. If 1 million horses were exported from the low-risk area with no post-arrival quarantine we estimate the median number of infected horses to be 5.4 (95% prediction interval 0.5 to 41). This equates to an annual probability of 0.0016 (95% PI: 0.00015 to 0.012) assuming 300 horses exported per year. An additional PCR test while in vector-protected post-arrival quarantine reduced these probabilities by approximately 12-fold. Probabilities for horses exported from an area where AHS is endemic were approximately 15 to 17 times higher than for horses exported from the low-risk area under comparable scenarios. The probability of undetected AHS infection in horses exported from an infected country can be minimised by appropriate risk management measures. The final choice of risk management measures depends on the level of risk acceptable to the importing country.
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Affiliation(s)
- Evan S. Sergeant
- AusVet Animal Health Services, Canberra, Australian Capital Territory, Australia
- * E-mail:
| | - John D. Grewar
- Veterinary Services, Western Cape Department of Agriculture, Elsenburg, South Africa
| | - Camilla T. Weyer
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Alan J. Guthrie
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
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Weyer CT, Joone C, Lourens CW, Monyai MS, Koekemoer O, Grewar JD, van Schalkwyk A, Majiwa PO, MacLachlan NJ, Guthrie AJ. Development of three triplex real-time reverse transcription PCR assays for the qualitative molecular typing of the nine serotypes of African horse sickness virus. J Virol Methods 2015; 223:69-74. [DOI: 10.1016/j.jviromet.2015.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 07/14/2015] [Accepted: 07/27/2015] [Indexed: 11/25/2022]
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Grewar JD, Thompson PN, Lourens CW, Guthrie AJ. Equine encephalosis in Thoroughbred foals on a South African stud farm. ACTA ACUST UNITED AC 2015; 82:966. [PMID: 26842364 PMCID: PMC6238798 DOI: 10.4102/ojvr.v82i1.966] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 08/11/2015] [Accepted: 08/18/2015] [Indexed: 11/01/2022]
Abstract
Thoroughbred foal body temperature data were collected from shortly after birth until shortly after weaning during the 2007/2008 season on a stud farm in the Western Cape Province of South Africa. Equine encephalosis (EE) caused by EE virus (EEV) serotype 4 (EEV-4) occurred in the foal group during the first autumn after their birth (March and April 2008). A descriptive study was undertaken to provide data on the EEV maternal antibody status, the association between pyrexia and EEV infection, and the incidence of infection amongst the foals prior to and during the episode. This included the frequent capturing of foal body temperature data and regular collection of serum and whole blood during pyretic episodes. Infection by EEV was determined using both virological and serological methods. A high EE incidence of at least 94% occurred amongst the foal cohort, despite the fact that 37% of foals had previously shown maternal antibody to EEV-4. Pyrexia in foals was not directly associated with EE infection and 41% of infected foals showed no detectable pyretic episode. Information obtained from this EE episode showed the high incidence of EEV infection in foals during the first autumn after their birth. Monitoring foal body temperature can alert farmers to outbreaks of infectious disease, such as EE. These results are relevant to the epidemiology of EE and facilitate greater understanding of it as a differential diagnosis of African horse sickness (AHS), given that EE and AHS have similar epidemiologic profiles.
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Affiliation(s)
- John D Grewar
- Western Cape Department of Agriculture: Veterinary Services, Elsenburg, South Africa; Department of Production Animal Studies, University of Pretoria, South Africa.
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Grewar JD, Weyer CT, Guthrie AJ, Koen P, Davey S, Quan M, Visser D, Russouw E, Bührmann G. The 2011 outbreak of African horse sickness in the African horse sickness controlled area in South Africa. J S Afr Vet Assoc 2013. [DOI: 10.4102/jsava.v84i1.973] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
African horse sickness (AHS) is a controlled animal disease in South Africa, and as a result of the high mortality rates experienced, outbreaks in the AHS controlled area in the Western Cape Province have a significant impact on affected properties as well as on the exportation of live horses from the AHS free zone in metropolitan Cape Town. An outbreak of AHS serotype 1 occurred in the surveillance zone of the AHS controlled area of the Western Cape during the summer of 2011. The epicentre of the outbreak was the town of Mamre in the magisterial district of Malmesbury and the outbreak was confined to a defined containment zone within this area by movement control of all equids and a blanket vaccination campaign. A total of 73 cases of AHS were confirmed during this outbreak, which included four confirmed subclinical cases. The morbidity rate for the outbreak was 16%with a mortality rate of 14%and a case fatality rate of 88%. Outbreak disease surveillance relied on agent identification using polymerase chain reaction (PCR)-based assays, which is novel for an AHS outbreak in South Africa. The source of this outbreak was never confirmed although it is believed to be associated with the illegal movement of an infected animal into the Mamre area. This detailed description of the outbreak provides a sound scientific basis to assist decision making in future AHS outbreaks in the AHS controlled area of South Africa and in countries where AHS is an exotic or emerging disease.
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Grewar JD, Allen JG, Guthrie AJ. Annual ryegrass toxicity in Thoroughbred horses in Ceres in the Western Cape Province, South Africa. J S Afr Vet Assoc 2010; 80:220-3. [PMID: 20458861 DOI: 10.4102/jsava.v80i4.211] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
An outbreak of annual ryegrass toxicity occurred on a Thoroughbred stud in Ceres in the Western Cape Province of South Africa. This is the 1st report of annual ryegrass toxicity in horses in South Africa, although the condition has been reported in cattle and sheep populations in the past. Annual ryegrass toxicity is characterised by a variety of neurological signs including tremors, convulsions, recumbency and in many cases death. The description of the outbreak includes the history, clinical presentation and treatment protocol administered during the outbreak. Various epidemiological variables and their influence in the outbreak are also considered.
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Affiliation(s)
- J D Grewar
- Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa
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