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Bhowmick S, Fritz ML, Smith RL. Host-feeding preferences and temperature shape the dynamics of West Nile virus: A mathematical model to predict the impacts of vector-host interactions and vector management on R 0. Acta Trop 2024; 258:107346. [PMID: 39111645 DOI: 10.1016/j.actatropica.2024.107346] [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: 06/04/2024] [Revised: 07/23/2024] [Accepted: 07/30/2024] [Indexed: 08/22/2024]
Abstract
West Nile virus (WNV) is prevalent across the United States, but its transmission patterns and spatio-temporal intensity vary significantly, particularly in the Eastern United States. For instance, Chicago has long been a hotspot for WNV cases due to its high cumulative incidence of infection, with the number of cases varying considerably from year to year. The abilities of host species to maintain and disseminate WNV, along with eco-epidemiological factors that influence vector-host contact rates underlie WNV transmission potential. There is growing evidence that several vectors exhibit strong feeding preferences towards different host communities. In our research study, we construct a process based weather driven ordinary differential equation (ODE) model to understand the impact of one vector species (Culex pipiens), its preferred avian and non-preferred human hosts on the basic reproduction number (R0). In developing this WNV transmission model, we account for the feeding index, which is defined as the relative preference of the vectors for taking blood meals from a competent avian host versus a non-competent mammalian host. We also include continuous introduction of infected agents into the model during the simulations as the introduction of WNV is not a single event phenomenon. We derive an analytic form of R0 to predict the conditions under which there will be an outbreak of WNV and the relationship between the feeding index and the efficacy of adulticide is highly nonlinear. In our mechanistic model, we also demonstrate that adulticide treatments produced significant reductions in the Culex pipiens population. Sensitivity analysis demonstrates that feeding index and rate of introduction of infected agents are two important factors beside the efficacy of adulticide. We validate our model by comparing simulations to surveillance data collected for the Culex pipiens complex in Cook County, Illinois, USA. Our results reveal that the interaction between the feeding index and mosquito abatement strategy is intricate, especially considering the fluctuating temperature conditions. This induces heterogeneous transmission patterns that need to be incorporated when modelling multi-host, multi-vector transmission models.
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Affiliation(s)
- Suman Bhowmick
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
| | - Megan Lindsay Fritz
- Department of Entomology, Institute for Advanced Computer Studies, University of Maryland, USA
| | - Rebecca Lee Smith
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA; Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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2
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Baldon L, de Mendonça S, Santos E, Marçal B, de Freitas AC, Rezende F, Moreira R, Sousa V, Comini S, Lima M, Ferreira F, de Almeida JP, Silva E, Amadou S, Rocha M, Leite T, Todjro Y, de Carvalho C, Santos V, Giovanetti M, Alcantara L, Moreira LA, Ferreira A. Suitable Mouse Model to Study Dynamics of West Nile Virus Infection in Culex quinquefasciatus Mosquitoes. Trop Med Infect Dis 2024; 9:201. [PMID: 39330890 PMCID: PMC11435581 DOI: 10.3390/tropicalmed9090201] [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: 06/26/2024] [Revised: 08/21/2024] [Accepted: 08/25/2024] [Indexed: 09/28/2024] Open
Abstract
West Nile Virus (WNV) poses a significant global public health threat as a mosquito-borne pathogen. While laboratory mouse models have historically played a crucial role in understanding virus biology, recent research has focused on utilizing immunocompromised models to study arboviruses like dengue and Zika viruses, particularly their interactions with Aedes aegypti mosquitoes. However, there has been a shortage of suitable mouse models for investigating WNV and St. Louis encephalitis virus interactions with their primary vectors, Culex spp. mosquitoes. Here, we establish the AG129 mouse (IFN α/β/γ R-/-) as an effective vertebrate model for examining mosquito-WNV interactions. Following intraperitoneal injection, AG129 mice exhibited transient viremia lasting several days, peaking on the second or third day post-infection, which is sufficient to infect Culex quinquefasciatus mosquitoes during a blood meal. We also observed WNV replication in the midgut and dissemination to other tissues, including the fat body, in infected mosquitoes. Notably, infectious virions were present in the saliva of a viremic AG129 mouse 16 days post-exposure, indicating successful transmission capacity. These findings highlight the utility of AG129 mice for studying vector competence and WNV-mosquito interactions.
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Affiliation(s)
- Lívia Baldon
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Silvana de Mendonça
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Ellen Santos
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Bruno Marçal
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Amanda Cupertino de Freitas
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Fernanda Rezende
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Rafaela Moreira
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
- Laboratório de Ecologia do Adoecimento & Florestas NUPEB/ICEB, Universidade Federal de Ouro Preto, Ouro Preto 35402-163, Brazil
| | - Viviane Sousa
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Sara Comini
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Mariana Lima
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Flávia Ferreira
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - João Paulo de Almeida
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Emanuele Silva
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Siad Amadou
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Marcele Rocha
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Thiago Leite
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Yaovi Todjro
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 6627-Pampulha, Belo Horizonte 31270-901, Brazil
| | - Camila de Carvalho
- Plataforma de Microscopia e Microanálises de Imagens, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Viviane Santos
- Plataforma de PCR em Tempo Real, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Marta Giovanetti
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
- Department of Sciences and Technologies for Sustainable Development and One Health, University of Campus Bio-Medico, 00128 Rome, Italy
| | - Luiz Alcantara
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Luciano A Moreira
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
| | - Alvaro Ferreira
- Mosquitos Vetores: Endossimbiontes e Interação Patógeno-Vetor, Instituto René Rachou-Fiocruz, Belo Horizonte 30190-002, Brazil
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3
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Dimas Martins A, Roberts M, Ten Bosch Q, Heesterbeek H. Indirect interaction between an endemic and an invading pathogen: A case study of Plasmodium and Usutu virus dynamics in a shared bird host population. Theor Popul Biol 2024; 157:118-128. [PMID: 38626854 DOI: 10.1016/j.tpb.2024.04.002] [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: 03/08/2023] [Revised: 03/28/2024] [Accepted: 04/05/2024] [Indexed: 04/21/2024]
Abstract
Infectious disease agents can influence each other's dynamics in shared host populations. We consider such influence for two mosquito-borne infections where one pathogen is endemic at the time that a second pathogen invades. We regard a setting where the vector has a bias towards biting host individuals infected with the endemic pathogen and where there is a cost to co-infected hosts. As a motivating case study, we regard Plasmodium spp., that cause avian malaria, as the endemic pathogen, and Usutu virus (USUV) as the invading pathogen. Hosts with malaria attract more mosquitoes compared to susceptible hosts, a phenomenon named vector bias. The possible trade-off between the vector-bias effect and the co-infection mortality is studied using a compartmental epidemic model. We focus first on the basic reproduction number R0 for Usutu virus invading into a malaria-endemic population, and then explore the long-term dynamics of both pathogens once Usutu virus has become established. We find that the vector bias facilitates the introduction of malaria into a susceptible population, as well as the introduction of Usutu in a malaria-endemic population. In the long term, however, both a vector bias and co-infection mortality lead to a decrease in the number of individuals infected with either pathogen, suggesting that avian malaria is unlikely to be a promoter of Usutu invasion. This proposed approach is general and allows for new insights into other negative associations between endemic and invading vector-borne pathogens.
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Affiliation(s)
- Afonso Dimas Martins
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands.
| | - Mick Roberts
- New Zealand Institute for Advanced Study and the Infectious Disease Research Centre, Massey University, Auckland, New Zealand
| | - Quirine Ten Bosch
- Quantitative Veterinary Epidemiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Hans Heesterbeek
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands
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4
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de Wit MM, Dimas Martins A, Delecroix C, Heesterbeek H, ten Bosch QA. Mechanistic models for West Nile virus transmission: a systematic review of features, aims and parametrization. Proc Biol Sci 2024; 291:20232432. [PMID: 38471554 PMCID: PMC10932716 DOI: 10.1098/rspb.2023.2432] [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: 10/30/2023] [Accepted: 02/14/2024] [Indexed: 03/14/2024] Open
Abstract
Mathematical models within the Ross-Macdonald framework increasingly play a role in our understanding of vector-borne disease dynamics and as tools for assessing scenarios to respond to emerging threats. These threats are typically characterized by a high degree of heterogeneity, introducing a range of possible complexities in models and challenges to maintain the link with empirical evidence. We systematically identified and analysed a total of 77 published papers presenting compartmental West Nile virus (WNV) models that use parameter values derived from empirical studies. Using a set of 15 criteria, we measured the dissimilarity compared with the Ross-Macdonald framework. We also retrieved the purpose and type of models and traced the empirical sources of their parameters. Our review highlights the increasing refinements in WNV models. Models for prediction included the highest number of refinements. We found uneven distributions of refinements and of evidence for parameter values. We identified several challenges in parametrizing such increasingly complex models. For parameters common to most models, we also synthesize the empirical evidence for their values and ranges. The study highlights the potential to improve the quality of WNV models and their applicability for policy by establishing closer collaboration between mathematical modelling and empirical work.
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Affiliation(s)
- Mariken M. de Wit
- Quantitative Veterinary Epidemiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Afonso Dimas Martins
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands
| | - Clara Delecroix
- Quantitative Veterinary Epidemiology, Wageningen University and Research, Wageningen, The Netherlands
- Department of Environmental Sciences, Wageningen University and Research, Wageningen, The Netherlands
| | - Hans Heesterbeek
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands
| | - Quirine A. ten Bosch
- Quantitative Veterinary Epidemiology, Wageningen University and Research, Wageningen, The Netherlands
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5
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Lamas ZS, Krichton M, Ryabov EV, Hawthorne DJ, Evans JD. Susceptible and infectious states for both vector and host in a dynamic pathogen-vector-host system. Proc Biol Sci 2024; 291:20232293. [PMID: 38196351 PMCID: PMC10777147 DOI: 10.1098/rspb.2023.2293] [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: 10/11/2023] [Accepted: 12/01/2023] [Indexed: 01/11/2024] Open
Abstract
Deformed wing virus (DWV) is a resurgent insect pathogen of honeybees that is efficiently transmitted by vectors and through host social contact. Continual transmission of DWV between hosts and vectors is required to maintain the pathogen within the population, and this vector-host-pathogen system offers unique disease transmission dynamics for pathogen maintenance between vectors and a social host. In a series of experiments, we measured vector-vector, host-host and host-vector transmission routes and show how these maintain DWV in honeybee populations. We found co-infestations on shared hosts allowed for movement of DWV from mite to mite. Additionally, two social behaviours of the honeybee, trophallaxis and cannibalization of pupae, provide routes for horizontal transmission from bee to bee. Circulation of the virus solely among hosts through communicable modes provides a reservoir of DWV for naïve Varroa to acquire and subsequently vector the pathogen. Our findings illustrate the importance of community transmission between hosts and vector transmission. We use these results to highlight the key avenues used by DWV during maintenance and infection and point to similarities with a handful of other infectious diseases of zoonotic and medical importance.
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Affiliation(s)
- Zachary S. Lamas
- Bee Research Laboratory, United States Department of Agriculture—Agricultural Research Service, Beltsville 06415, MD, USA
- Department of Entomology, University of Maryland, College Park 20742-5031, MD, USA
| | - Maiya Krichton
- Bee Research Laboratory, United States Department of Agriculture—Agricultural Research Service, Beltsville 06415, MD, USA
- Department of Entomology, University of Maryland, College Park 20742-5031, MD, USA
| | - Eugene V. Ryabov
- Bee Research Laboratory, United States Department of Agriculture—Agricultural Research Service, Beltsville 06415, MD, USA
- Department of Entomology, University of Maryland, College Park 20742-5031, MD, USA
- The James Hutton Institute, Invergowrie, Dundee, UK
| | - David J. Hawthorne
- Department of Entomology, University of Maryland, College Park 20742-5031, MD, USA
| | - Jay D. Evans
- Bee Research Laboratory, United States Department of Agriculture—Agricultural Research Service, Beltsville 06415, MD, USA
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Blanquer A, Rivas F, Gérardy M, Sarlet M, Moula N, Ziegler U, Groschup MH, Desmecht D, Marichal T, Garigliany M. Evaluation of Non-Vector Transmission of Usutu Virus in Domestic Canaries ( Serinus canaria). Viruses 2024; 16:79. [PMID: 38257779 PMCID: PMC10819963 DOI: 10.3390/v16010079] [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: 11/10/2023] [Revised: 12/21/2023] [Accepted: 12/22/2023] [Indexed: 01/24/2024] Open
Abstract
Usutu virus (USUV) is a flavivirus transmitted to avian species through mosquito bites that causes mass mortalities in wild and captive bird populations. However, several cases of positive dead birds have been recorded during the winter, a vector-free period. To explain how USUV "overwinters", the main hypothesis is bird-to-bird transmission, as shown for the closely related West Nile virus. To address this question, we experimentally challenged canaries with intranasal inoculation of USUV, which led to systemic dissemination of the virus, provided the inoculated dose was sufficient (>102 TCID50). We also highlighted the oronasal excretion of infectious viral particles in infected birds. Next, we co-housed infected birds with naive sentinels, to determine whether onward transmission could be reproduced experimentally. We failed to detect such transmission but demonstrated horizontal transmission by transferring sputum from an infected to a naive canary. In addition, we evaluated the cellular tropism of respiratory mucosa to USUV in vitro using a canary tracheal explant and observed only limited evidence of viral replication. Further research is then needed to assess if and how comparable bird-to-bird transmission occurs in the wild.
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Affiliation(s)
- Aude Blanquer
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
| | - Felipe Rivas
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
| | - Mazarine Gérardy
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
| | - Michaël Sarlet
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
| | - Nassim Moula
- Animal Resources Veterinary Management Department, Faculty of Veterinary Medicine, GIGA Research (AFT), Sart Tilman B23B, B-4000 Liège, Belgium;
| | - Ute Ziegler
- Friedrich-Loeffler-Institut, Institute for Novel and Emerging Infectious Diseases, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (U.Z.); (M.H.G.)
| | - Martin H. Groschup
- Friedrich-Loeffler-Institut, Institute for Novel and Emerging Infectious Diseases, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (U.Z.); (M.H.G.)
| | - Daniel Desmecht
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
| | - Thomas Marichal
- Laboratory of Immunophysiology, GIGA Institute, University of Liège, B-4000 Liège, Belgium;
- Faculty of Veterinary Medicine, University of Liège, Sart Tilman B42, B-4000 Liège, Belgium
| | - Mutien Garigliany
- Fundamental and Applied Research for Animals & Health (FARAH), Laboratory of Pathology, Faculty of Veterinary Medicine, University of Liège, Sart Tilman B43, B-4000 Liège, Belgium; (A.B.); (F.R.); (M.G.); (M.S.); (D.D.)
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Ferraguti M, Dimas Martins A, Artzy-Randrup Y. Quantifying the invasion risk of West Nile virus: Insights from a multi-vector and multi-host SEIR model. One Health 2023; 17:100638. [PMID: 38024254 PMCID: PMC10665159 DOI: 10.1016/j.onehlt.2023.100638] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023] Open
Abstract
The invasion of vector-borne diseases depends on the type of specific features of the vector and hosts at play. Within the Culex pipiens complex, differences in ecology, biology, and vector competence can influence the risk of West Nile virus (WNV) outbreaks. To determine which life-history traits affect WNV invasion into susceptible communities the most, we constructed an epidemiological Susceptible-Exposed-Infectious-Recovered model with three vector (eco)types, Culex pipiens pipiens, Cx. pip. molestus, and their hybrids, and two vertebrate hosts, birds (as amplifying hosts) and humans (as dead-end hosts). We investigated how differences in feeding preferences and transmission rates influenced WNV transmission across different habitats and two seasons (Spring versus Summer), to investigate the impact of increasing mosquitoes on the WNV transmission risk. Our results showed that vector feeding preferences and the transmission rate between mosquitoes and birds were the parameters that most influenced WNV invasion risk. Even though our model did not predict WNV invasion across any of the studied environments, we found that natural habitats displayed the highest susceptibility to WNV invasion. Pipiens (eco)type acted as the primary vector in all habitats. Hybrids, contrary to common opinion, showed minimal involvement in WNV transmission. However, it is important to interpret our study results with caution due to the possibility of idealized spring and summer seasons being reflected in the field-collected data. Our study could be a tool to enhance current vector surveillance and control programs by targeting specific vector types in specific environments, especially in natural habitat, which are most responsive to environmental shifts. The joint approach based on epidemiological modelling based on field collected data can help to reduce wasted time and economic costs while maximizing the efficiency of local public health authorities.
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Affiliation(s)
- Martina Ferraguti
- Departamento de Biología de la Conservación y Cambio Global, Estación Biológica de Doñana (EBD), CSIC, C/Américo Vespucio, 26, E-41092 Seville, Spain
- Department of Theoretical and Computational Ecology (TCE), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands
- CIBER of Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - Afonso Dimas Martins
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 7, 3584 CL Utrecht, the Netherlands
| | - Yael Artzy-Randrup
- Department of Theoretical and Computational Ecology (TCE), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands
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8
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Flores-Ferrer A, Suzán G, Waleckx E, Gourbière S. Assessing the risk of West Nile Virus seasonal outbreaks and its vector control in an urbanizing bird community: An integrative R0-modelling study in the city of Merida, Mexico. PLoS Negl Trop Dis 2023; 17:e0011340. [PMID: 37253060 PMCID: PMC10256229 DOI: 10.1371/journal.pntd.0011340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 06/09/2023] [Accepted: 04/27/2023] [Indexed: 06/01/2023] Open
Abstract
Urbanization is a global trend associated with key socio-economic issues, one of them being to control the transmission of infectious diseases to a urban fraction of the world's population that shall reach 68% in 2050. While urban growth has been shown to favor mosquito species responsible for the transmission of the West Nile Virus (WNV), a major human arbovirosis, the effects of concomitant changes in the host bird communities remain hard to anticipate albeit essential to quantify disease risk and to plan control initiatives. We developed a R0 modelling of WNV transmission in a urban bird community to assess the risk of outbreak in Merida, one of the cities with the highest growth rate in Mexico. The model was parameterized using ecological and epidemiological data collected over the past 15-years on the local vector, Culex quinquefasciatus, and avian community. We identified a 3-weeks summer period during which the vector population strongly amplifies the WNV enzootic transmission and lead to a significant risk of outbreaks in humans. Extensive sensitivity analyses showed that urbanization induced changes in the bird community could lead to an up-to 6-fold increase in the duration of the risk period, while the daily risk could rise by 40%. Interestingly, the increase in Quiscalus mexicanus abundance had 4-5 times larger impact than any other change in the bird community. In such a context, annihilating the current and future risk of WNV outbreaks in Merida requires reducing the mosquito population by 13% and up to 56%, respectively. This study provides an integrative assessment of the current and future risks of WNV outbreak in the fast urbanizing city of Merida, and points toward the implementation of epidemiological monitoring combined with preemptive measures targeting both C. quinquefasciatus and Q. mexicanus populations, as they are expected to have synergistic effects.
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Affiliation(s)
- Alheli Flores-Ferrer
- Departamento de Etología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, México
- International Joint Laboratory ELDORADO, IRD/UNAM, Mérida, Yucatán, México
| | - Gerardo Suzán
- Departamento de Etología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, México
- International Joint Laboratory ELDORADO, IRD/UNAM, Mérida, Yucatán, México
| | - Etienne Waleckx
- Institut de Recherche pour le Développement, UMR INTERTRYP IRD, CIRAD, Université de Montpellier, Montpellier, France
- Laboratorio de Parasitología, Centro de Investigaciones Regionales ‘Dr. Hideyo Noguchi’, Universidad Autónoma deYucatán, Mérida, Yucatán, México
| | - Sébastien Gourbière
- UMR5096 ‘Laboratoire Génome et Développement des Plantes’, Université de Perpignan Via Domitia, Perpignan, France
- School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
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9
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Dimas Martins A, ten Bosch Q, Heesterbeek JAP. Exploring the influence of competition on arbovirus invasion risk in communities. PLoS One 2022; 17:e0275687. [PMID: 36223367 PMCID: PMC9555654 DOI: 10.1371/journal.pone.0275687] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 09/22/2022] [Indexed: 11/18/2022] Open
Abstract
Arbovirus outbreaks in communities are affected by how vectors, hosts and non-competent species interact. In this study, we investigate how ecological interactions between species and epidemiological processes influence the invasion potential of a vector-borne disease. We use an eco-epidemiological model to explore the basic reproduction number R0 for a range of interaction strengths in key processes, using West Nile virus infection to parameterize the model. We focus our analysis on intra and interspecific competition between vectors and between hosts, as well as competition with non-competent species. We show that such ecological competition has non-linear effects on R0 and can greatly impact invasion risk. The presence of multiple competing vector species results in lower values for R0 while host competition leads to the highest values of risk of disease invasion. These effects can be understood in terms of how the competitive pressures influence the vector-to-host ratio, which has a positive relationship with R0. We also show numerical examples of how vector feeding preferences become more relevant in high competition conditions between hosts. Under certain conditions, non-competent hosts, which can lead to a dilution effect for the pathogen, can have an amplification effect if they compete strongly with the competent hosts, hence facilitating pathogen invasion in the community.
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Affiliation(s)
- Afonso Dimas Martins
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands,* E-mail:
| | - Quirine ten Bosch
- Quantitative Veterinary Epidemiology, Wageningen University and Research, Wageningen, The Netherlands
| | - J. A. P. Heesterbeek
- Department of Population Health Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands
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10
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Abstract
West Nile virus (WNV) is a mosquito-borne flavivirus with a global distribution that is maintained in an enzootic cycle between Culex species mosquitoes and avian hosts. Human infection, which occurs as a result of spillover from this cycle, is generally subclinical or results in a self-limiting febrile illness. Central nervous system infection occurs in a minority of infections and can lead to long-term neurological complications and, rarely, death. WNV is the most prevalent arthropod-borne virus in the United States. Climate change can influence several aspects of WNV transmission including the vector, amplifying host, and virus. Climate change is broadly predicted to increase WNV distribution and risk across the globe, yet there will likely be significant regional variability and limitations to this effect. Increases in temperature can accelerate mosquito and pathogen development, drive increases in vector competence for WNV, and also alter mosquito life history traits including longevity, blood feeding behavior and fecundity. Precipitation, humidity and drought also impact WNV transmissibility. Alteration in avian distribution, diversity and phenology resulting from climate variation add additional complexity to these relationships. Here, we review WNV epidemiology, transmission, disease and genetics in the context of laboratory studies, field investigations, and infectious disease models under climate change. We summarize how mosquito genetics, microbial interactions, host dynamics, viral strain, population size, land use and climate account for distinct relationships that drive WNV activity and discuss how these dynamic and evolving interactions could shape WNV transmission and disease under climate change.
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Affiliation(s)
- Rachel L Fay
- The Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, Slingerlands, NY, United States; Department of Biomedical Sciences, State University of New York at Albany School of Public Health, Rensselaer, NY, United States
| | - Alexander C Keyel
- The Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, Slingerlands, NY, United States; Department of Atmospheric and Environmental Sciences, State University of New York at Albany, Albany, NY, United States
| | - Alexander T Ciota
- The Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, Slingerlands, NY, United States; Department of Biomedical Sciences, State University of New York at Albany School of Public Health, Rensselaer, NY, United States.
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11
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Di Pol G, Crotta M, Taylor RA. Modelling the temperature suitability for the risk of West Nile Virus establishment in European Culex pipiens populations. Transbound Emerg Dis 2022; 69:e1787-e1799. [PMID: 35304820 PMCID: PMC9790397 DOI: 10.1111/tbed.14513] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 03/02/2022] [Accepted: 03/13/2022] [Indexed: 12/31/2022]
Abstract
Increases in temperature and extreme weather events due to global warming can create an environment that is beneficial to mosquito populations, changing and possibly increasing the suitable geographical range for many vector-borne diseases. West Nile Virus (WNV) is a flavivirus, maintained in a mosquito-avian host cycle that is usually asymptomatic but can cause primarily flu-like symptoms in human and equid accidental hosts. In rare circumstances, serious disease and death are possible outcomes for both humans and horses. The main European vector of WNV is the Culex pipiens mosquito. This study examines the effect of environmental temperature on WNV establishment in Europe via Culex pipiens populations through use of a basic reproduction number ( R 0 ${R_0}$ ) model. A metric of thermal suitability derived from R 0 ${R_0}$ was developed by collating thermal responses of different Culex pipiens traits and combining them through use of a next-generation matrix. WNV establishment was determined to be possible between 14°C and 34.3°C, with the optimal temperature at 23.7°C. The suitability measure was plotted against monthly average temperatures in 2020 and the number of months with high suitability mapped across Europe. The average number of suitable months for each year from 2013 to 2019 was also calculated and validated with reported equine West Nile fever cases from 2013 to 2019. The widespread thermal suitability for WNV establishment highlights the importance of European surveillance for this disease and the need for increased research into mosquito and bird distribution.
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Affiliation(s)
- Gabriella Di Pol
- Veterinary Epidemiology, Economics and Public Health GroupDepartment of Pathobiology and Population SciencesRoyal Veterinary CollegeLondonUK
| | - Matteo Crotta
- Veterinary Epidemiology, Economics and Public Health GroupDepartment of Pathobiology and Population SciencesRoyal Veterinary CollegeLondonUK
| | - Rachel A. Taylor
- Department of Epidemiological SciencesAnimal and Plant Health AgencySurreyUK
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12
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Petrucciani A, Yu G, Ventresca M. Multi-season transmission model of Eastern Equine Encephalitis. PLoS One 2022; 17:e0272130. [PMID: 35976903 PMCID: PMC9385034 DOI: 10.1371/journal.pone.0272130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 07/12/2022] [Indexed: 12/03/2022] Open
Abstract
Eastern Equine Encephalitis (EEE) is an arbovirus that, while it has been known to exist since the 1930's, recently had a spike in cases. This increased prevalence is particularly concerning due to the severity of the disease with 1 in 3 symptomatic patients dying. The cause of this peak is currently unknown but could be due to changes in climate, the virus itself, or host behavior. In this paper we propose a novel multi-season deterministic model of EEE spread and its stochastic counterpart. Models were parameterized using a dataset from the Florida Department of Health with sixteen years of sentinel chicken seroconversion rates. The different roles of the enzootic and bridge mosquito vectors were explored. As expected, enzootic mosquitoes like Culiseta melanura were more important for EEE persistence, while bridge vectors were implicated in the disease burden in humans. These models were used to explore hypothetical viral mutations and host behavior changes, including increased infectivity, vertical transmission, and host feeding preferences. Results showed that changes in the enzootic vector transmission increased cases among birds more drastically than equivalent changes in the bridge vector. Additionally, a 5% difference in the bridge vector's bird feeding preference can increase cumulative dead-end host infections more than 20-fold. Taken together, this suggests changes in many parts of the transmission cycle can augment cases in birds, but the bridge vectors feeding preference acts as a valve limiting the enzootic circulation from its impact on dead-end hosts, such as humans. Our what-if scenario analysis reveals and measures possible threats regarding EEE and relevant environmental changes and hypothetically suggests how to prevent potential damage to public health and the equine economy.
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Affiliation(s)
- Alexa Petrucciani
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Geonsik Yu
- School of Industrial Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Mario Ventresca
- School of Industrial Engineering, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Institute for Inflammation, Immunology, and Infectious Diseases, Purdue University, West Lafayette, Indiana, United States of America
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13
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Bhowmick S, Gethmann J, Conraths FJ, Sokolov IM, Lentz HHK. Locally temperature - driven mathematical model of West Nile virus spread in Germany. J Theor Biol 2019; 488:110117. [PMID: 31866397 DOI: 10.1016/j.jtbi.2019.110117] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 11/22/2019] [Accepted: 12/12/2019] [Indexed: 01/06/2023]
Abstract
West Nile virus (WNV) is an arthropod-borne virus (arbovirus) transmitted by the bites of infected mosquitoes. WNV can also infect horses and humans, where it may cause serious illness and can be fatal. Birds are the natural reservoir, and humans, equines and probably other mammals are dead-end hosts. In 2018, WNV occurred for the first time in Germany, affecting birds and horses. Seroconversion of an exposed veterinarian has also been reported. It is therefore of importance to evaluate the circumstances, under which WNV may establish in Germany as a whole or in particular favourable regions. In our current work, we formulate a dynamic model to describe the spreading process of West Nile virus in the presence of migratory birds. To investigate the possible role of migratory birds in the dissemination of WNV in Germany, we include the recurring presence of migratory birds through a mechanistic ordinary differential equations (ODE) model system. We also perform a sensitivity analysis of the infection curves. Seasonal impacts are also taken into consideration. As result, we present an analytical expression for the basic reproduction number R0. We find that after introducing WNV into Germany, R0 will be above the critical value in many regions of the country. Furthermore, we observe that in the south of Germany, the disease reoccurs in the following season after the introduction. We include a potential distribution map associated with WNV cases in Germany to illustrate our findings in a spatial scale.
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Affiliation(s)
- Suman Bhowmick
- Friedrich-Loeffler-Institut, Institute of Epidemiology, Südufer 10, Greifswald 17493, Germany; Institute of Physics, Humboldt University of Berlin, Newtonstraße 15, Berlin 12489, Germany
| | - Jörn Gethmann
- Friedrich-Loeffler-Institut, Institute of Epidemiology, Südufer 10, Greifswald 17493, Germany
| | - Franz J Conraths
- Friedrich-Loeffler-Institut, Institute of Epidemiology, Südufer 10, Greifswald 17493, Germany
| | - Igor M Sokolov
- Institute of Physics, Humboldt University of Berlin, Newtonstraße 15, Berlin 12489, Germany
| | - Hartmut H K Lentz
- Friedrich-Loeffler-Institut, Institute of Epidemiology, Südufer 10, Greifswald 17493, Germany.
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14
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West Nile virus transmission and human infection risk in Veneto (Italy): a modelling analysis. Sci Rep 2018; 8:14005. [PMID: 30228340 PMCID: PMC6143586 DOI: 10.1038/s41598-018-32401-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 09/07/2018] [Indexed: 11/08/2022] Open
Abstract
An intensified and continuous West Nile virus (WNV) spread across northern Italy has been observed since 2008, which caused more than one hundred reported human infections until 2016. Veneto is one of the Italian regions where WNV is considered endemic, and the greatest intensity of circulation was observed during 2013 and 2016. By using entomological data collected across the region in those years, we calibrated a temperature-driven mathematical model through a Bayesian approach that simulates the WNV infection in an avian population with seasonal demography. We considered two alternative routes of life cycle re-activation of the virus at the beginning of each vector breeding season: in the first one the virus is maintained by infected birds, in the other by diapausing mosquitoes previously infected. Afterwards, we computed seasonal risk curves for human infection and quantified how they translate into reported symptomatic cases. According to our results, WNV is more likely to be re-activated each year via previously infected mosquitoes. The highest probability of human infection is expected to occur in August, consistently with observations. Our epidemiological estimates can be of particular interest for public health authorities, to support decisions in term of designing efficient surveillance plans and preventive measures.
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15
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Overwintering of West Nile virus in a bird community with a communal crow roost. Sci Rep 2018; 8:6088. [PMID: 29666401 PMCID: PMC5904116 DOI: 10.1038/s41598-018-24133-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/22/2018] [Indexed: 02/04/2023] Open
Abstract
In temperate climates, transmission of West Nile virus (WNV) is detectable rarely during the coldest months (late fall through early spring), yet the virus has reappeared consistently during the next warm season. Several mechanisms may contribute to WNV persistence through winter, including bird-to-bird transmission among highly viremic species. Here we consider whether, under realistic scenarios supported by field and laboratory evidence, a winter bird community could sustain WNV through the winter in the absence of mosquitoes. With this purpose we constructed a deterministic model for a community of susceptible birds consisting of communally roosting crows, raptors and other birds. We simulated WNV introduction and subsequent transmission dynamics during the winter under realistic initial conditions and model parameterizations, including plausible contact rates for roosting crows. Model results were used to determine whether the bird community could yield realistic outbreaks that would result in WNV infectious individuals at the end of the winter, which would set up the potential for onward horizontal transmission into summer. Our findings strongly suggest that winter crow roosts could allow for WNV persistence through the winter, and our model results provide synthesis to explain inconclusive results from field studies on WNV overwintering in crow roosts.
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16
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Tran A, L'Ambert G, Balança G, Pradier S, Grosbois V, Balenghien T, Baldet T, Lecollinet S, Leblond A, Gaidet-Drapier N. An Integrative Eco-Epidemiological Analysis of West Nile Virus Transmission. ECOHEALTH 2017; 14:474-489. [PMID: 28584951 PMCID: PMC5662683 DOI: 10.1007/s10393-017-1249-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Accepted: 04/26/2017] [Indexed: 06/07/2023]
Abstract
West Nile disease, caused by the West Nile virus (WNV), is a mosquito-borne zoonotic disease affecting humans and horses that involves wild birds as amplifying hosts. The mechanisms of WNV transmission remain unclear in Europe where the occurrence of outbreaks has dramatically increased in recent years. We used a dataset on the competence, distribution, abundance, diversity and dispersal of wild bird hosts and mosquito vectors to test alternative hypotheses concerning the transmission of WNV in Southern France. We modelled the successive processes of introduction, amplification, dispersal and spillover of WNV to incidental hosts based on host-vector contact rates on various land cover types and over four seasons. We evaluated the relative importance of the mechanisms tested using two independent serological datasets of WNV antibodies collected in wild birds and horses. We found that the same transmission processes (seasonal virus introduction by migratory birds, Culex modestus mosquitoes as amplifying vectors, heterogeneity in avian host competence, absence of 'dilution effect') best explain the spatial variations in WNV seroprevalence in the two serological datasets. Our results provide new insights on the pathways of WNV introduction, amplification and spillover and the contribution of bird and mosquito species to WNV transmission in Southern France.
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Affiliation(s)
- Annelise Tran
- CIRAD, UPR AGIRs, Montpellier, France.
- CIRAD, UPR TETIS, Montpellier, France.
- CYROI, Sainte-Clotilde, Reunion Island, France.
| | | | | | - Sophie Pradier
- Ecole Nationale Vétérinaire de Toulouse, Toulouse, France
| | | | | | | | | | - Agnès Leblond
- Université de Lyon, Marcy-l'Etoile, France
- INRA, Saint Genès Champanelle, France
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17
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Modelling West Nile virus transmission risk in Europe: effect of temperature and mosquito biotypes on the basic reproduction number. Sci Rep 2017; 7:5022. [PMID: 28694450 PMCID: PMC5504010 DOI: 10.1038/s41598-017-05185-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 05/25/2017] [Indexed: 12/31/2022] Open
Abstract
West Nile virus (WNV) is a mosquito-borne flavivirus which has caused repeated outbreaks in humans in southern and central Europe, but thus far not in northern Europe. The main mosquito vector for WNV, Culex pipiens, consists of two behaviourally distinct biotypes, pipiens and molestus, which can form hybrids. Differences between biotypes, such as vector competence and host preference, could be important in determining the risk of WNV outbreaks. Risks for WNV establishment can be modelled with basic reproduction number (R0) models. However, existing R0 models have not differentiated between biotypes. The aim of this study was, therefore, to explore the role of temperature-dependent and biotype-specific effects on the risk of WNV establishment in Europe. We developed an R0 model with temperature-dependent and biotype-specific parameters, and calculated R0 values using the next-generation matrix for several scenarios relevant for Europe. In addition, elasticity analysis was done to investigate the contribution of each biotype to R0. Global warming and increased mosquito-to-host ratios can possibly result in more intense WNV circulation in birds and spill-over to humans in northern Europe. Different contributions of the Cx. pipiens biotypes to R0 shows the importance of including biotype-specific parameters in models for reliable WNV risk assessments.
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18
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Marini G, Rosá R, Pugliese A, Heesterbeek H. Exploring vector-borne infection ecology in multi-host communities: A case study of West Nile virus. J Theor Biol 2016; 415:58-69. [PMID: 27986465 DOI: 10.1016/j.jtbi.2016.12.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 12/07/2016] [Accepted: 12/10/2016] [Indexed: 10/20/2022]
Abstract
In this study, we develop a model to investigate how ecological factors might affect the dynamics of a vector-borne pathogen in a population composed by different hosts which interact with each other. Specifically, we consider the case when different host species compete with each other, as they share the same habitat, and the vector might have different feeding preference, which can also be time dependent. As a prototypical example, we apply our model to study the invasion and spread, during a typical season, of West Nile virus in an ecosystem composed of two competent avian host species and possibly of dead-end host species. We found that competition and vector feeding preferences can profoundly influence pathogen invasion, influencing its probability to start an epidemic, and influencing transmission rates. Finally, when considering time-dependent feeding preferences, as observed in the field, we noted that the virus circulation could be amplified and that the timing of epidemic peaks could be changed. Our work highlights that ecological interactions between hosts can have a profound influence on the dynamics of the pathogen and that, when modeling vector-borne infections, vector feeding behavior should, for this reason, be carefully evaluated.
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Affiliation(s)
- Giovanni Marini
- Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 San Michele all'Adige, TN, Italy; Department of Mathematics, University of Trento, via Sommarive 14, 38123 Povo, Trento, Italy.
| | - Roberto Rosá
- Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 San Michele all'Adige, TN, Italy
| | - Andrea Pugliese
- Department of Mathematics, University of Trento, via Sommarive 14, 38123 Povo, Trento, Italy
| | - Hans Heesterbeek
- Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 7, 3584 CL Utrecht, The Netherlands
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19
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Hartemink N, Cianci D, Reiter P. R0 for vector-borne diseases: impact of the assumption for the duration of the extrinsic incubation period. Vector Borne Zoonotic Dis 2015; 15:215-7. [PMID: 25793478 DOI: 10.1089/vbz.2014.1684] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mathematical modeling and notably the basic reproduction number R0 have become popular tools for the description of vector-borne disease dynamics. We compare two widely used methods to calculate the probability of a vector to survive the extrinsic incubation period. The two methods are based on different assumptions for the duration of the extrinsic incubation period; one method assumes a fixed period and the other method assumes a fixed daily rate of becoming infectious. We conclude that the outcomes differ substantially between the methods when the average life span of the vector is short compared to the extrinsic incubation period.
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Affiliation(s)
- Nienke Hartemink
- 1 Faculty of Veterinary Medicine, Utrecht University , Utrecht, The Netherlands
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20
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Does host receptivity or host exposure drives dynamics of infectious diseases? The case of West Nile Virus in wild birds. INFECTION GENETICS AND EVOLUTION 2015; 33:11-9. [PMID: 25891281 DOI: 10.1016/j.meegid.2015.04.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 03/28/2015] [Accepted: 04/10/2015] [Indexed: 11/21/2022]
Abstract
Infection is a complex biological process involving reciprocally both the intensity of host exposure to a pathogen as well as the host intrinsic "receptivity", or permissiveness to infection. Disentangling their respective contributions is currently seen as a fundamental gap in our knowledge. Here, we take the advantage of a rare semi-natural experiment context provided by the emergence of the West Nile Virus (WNV) in North America. Focusing on the pathogen emergence period, we combine datasets from (i) wild birds exposed to WNV in an urban zoo to evaluate the species intrinsic receptivity to WNV infection in an environment where exposure to WNV vectors can be assumed to be relatively homogenous for all captive species, and (ii) from free-ranging birds in their natural habitat where species ecological traits is expected to influence their exposure to WNV vectors. We show that ecological trait and intrinsic receptivity to infection both contribute similarly to the species variation in WNV seroprevalence, but considering only one of them can lead to erroneous conclusions. We then argue that degree of pathogen host specialization could be a fundamental factor for the respective contribution of species exposure and receptivity for numerous pathogens.
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21
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Al-Zoughool M, Cottrell D, Elsaadany S, Murray N, Oraby T, Smith R, Krewski D. Mathematical Models for Estimating the Risks of Bovine Spongiform Encephalopathy (BSE). JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2015; 18:71-104. [PMID: 26158300 DOI: 10.1080/10937404.2015.1036963] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
When the bovine spongiform encephalopathy (BSE) epidemic first emerged in the United Kingdom in the mid 1980s, the etiology of animal prion diseases was largely unknown. Risk management efforts to control the disease were also subject to uncertainties regarding the extent of BSE infections and future course of the epidemic. As understanding of BSE increased, mathematical models were developed to estimate risk of BSE infection and to predict reductions in risk in response to BSE control measures. Risk models of BSE-transmission dynamics determined disease persistence in cattle herds and relative infectivity of cattle prior to onset of clinical disease. These BSE models helped in understanding key epidemiological features of BSE transmission and dynamics, such as incubation period distribution and age-dependent infection susceptibility to infection with the BSE agent. This review summarizes different mathematical models and methods that have been used to estimate risk of BSE, and discusses how such risk projection models have informed risk assessment and management of BSE. This review also provides some general insights on how mathematical models of the type discussed here may be used to estimate risks of emerging zoonotic diseases when biological data on transmission of the etiological agent are limited.
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Affiliation(s)
- Mustafa Al-Zoughool
- a Department of Community and Environmental Health , King Saud Bin Abdulaziz University for Health Sciences , Riyadh , Saudi Arabia
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22
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Cordovez JM, Sanabria C. Environmental changes can produce shifts in chagas disease infection risk. ENVIRONMENTAL HEALTH INSIGHTS 2014; 8:43-48. [PMID: 25574142 PMCID: PMC4266202 DOI: 10.4137/ehi.s16002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 09/10/2014] [Accepted: 09/12/2014] [Indexed: 06/04/2023]
Abstract
An epidemiological network contains all the organisms involved (types) in the transmission of a parasite. The nodes of the network represent reservoirs, hosts, and vectors, while the links between the nodes represent the strength and direction of parasite movement. Networks that contain humans are of special interest because they are of concern to public health authorities. Under these circumstances, it is possible, in principle, to identify cycles (closed paths in the network) that include humans and select the ones that carry the maximum probability of human infection. The basic reproduction number R 0 in such a network gives the average number of new infections of any type after the introduction of one individual infected by any type. To obtain R 0 for complex networks, one can use the next-generation matrix (NGM) approach. Every entry in NGM will average the contribution of each link that connects two types. To tease the contribution of every cycle apart, we define the virulence as the geometric mean of the NGM entries corresponding to the links therein. This approach allows for the quantification of specific cycles of interest while it also makes the computation of the sensitivity and elasticity of the parameters easier. In this work, we compute the virulence for the transmission dynamics of Chagas disease for a typical rural area in Colombia incorporating the effect of environmental changes on the vector population size. We concluded that the highest contribution to human infection comes from humans themselves, which is a surprising and interesting result. In addition, sensitivity analysis revealed that increasing vector population size increases the risk of human infection.
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Affiliation(s)
- Juan M Cordovez
- Departamento de Ingeniería Biomédica, Universidad de los Andes, Bogotá D.C., Colombia
| | - Camilo Sanabria
- Departamento de Matemáticas, Universidad de los Andes, Bogotá D.C., Colombia
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23
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Cordovez JM, Rendon LM, Gonzalez C, Guhl F. Using the basic reproduction number to assess the effects of climate change in the risk of Chagas disease transmission in Colombia. Acta Trop 2014; 129:74-82. [PMID: 24416781 DOI: 10.1016/j.actatropica.2013.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The dynamics of vector-borne diseases has often been linked to climate change. However the commonly complex dynamics of vector-borne diseases make it very difficult to predict risk based on vector or host distributions. The basic reproduction number (R0) integrates all factors that determine whether a pathogen can establish or not. To obtain R0 for complex vector-borne diseases one can use the next-generation matrix (NGM) approach. We used the NGM to compute R0 for Chagas disease in Colombia incorporating the effect of temperature in some of the transmission routes of Trypanosoma cruzi. We used R0 to generate a risk map of present conditions and a forecast risk map at 20 years from now based on mean annual temperature (data obtained from Worldclim). In addition we used the model to compute elasticity and sensitivity indexes on all model parameters and routes of transmission. We present this work as an approach to indicate which transmission pathways are more critical for disease transmission but acknowledge the fact that results and projections strongly depend on better knowledge of entomological parameters and transmission routes. We concluded that the highest contribution to R0 comes from transmission of the parasites from humans to vectors, which is a surprising result. In addition,parameters related to contacts between human and vectors and the efficiency of parasite transmission between them also show a prominent effect on R0.
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Marka A, Diamantidis A, Papa A, Valiakos G, Chaintoutis SC, Doukas D, Tserkezou P, Giannakopoulos A, Papaspyropoulos K, Patsoula E, Badieritakis E, Baka A, Tseroni M, Pervanidou D, Papadopoulos NT, Koliopoulos G, Tontis D, Dovas CI, Billinis C, Tsakris A, Kremastinou J, Hadjichristodoulou C. West Nile virus state of the art report of MALWEST Project. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2013; 10:6534-610. [PMID: 24317379 PMCID: PMC3881129 DOI: 10.3390/ijerph10126534] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 11/11/2013] [Accepted: 11/12/2013] [Indexed: 11/16/2022]
Abstract
During the last three years Greece is experiencing the emergence of West Nile virus (WNV) epidemics. Within this framework, an integrated surveillance and control programme (MALWEST project) with thirteen associate partners was launched aiming to investigate the disease and suggest appropriate interventions. One out of seven work packages of the project is dedicated to the State of the Art report for WNV. Three expert working groups on humans, animals and mosquitoes were established. Medical databases (PubMed, Scopus) were searched together with websites: e.g., WHO, CDC, ECDC. In total, 1,092 relevant articles were initially identified and 258 of them were finally included as references regarding the current knowledge about WNV, along with 36 additional sources (conference papers, reports, book chapters). The review is divided in three sections according to the fields of interest: (1) WNV in humans (epidemiology, molecular characteristics, transmission, diagnosis, treatment, prevention, surveillance); (2) WNV in animals (epidemiological and transmission characteristics concerning birds, horses, reptiles and other animal species) and (3) WNV in mosquitoes (control, surveillance). Finally, some examples of integrated surveillance programmes are presented. The introduction and establishment of the disease in Greece and other European countries further emphasizes the need for thorough research and broadening of our knowledge on this viral pathogen.
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Affiliation(s)
- Andriani Marka
- Department of Microbiology, Faculty of Medicine, University of Athens, Athens 11527, Greece; E-mail:
| | - Alexandros Diamantidis
- Laboratory of Entomology and Agricultural Zoology, School of Agricultural Sciences, University of Thessaly, Volos 38446, Greece; E-mails: (A.D.); (N.T.P.)
| | - Anna Papa
- National Reference Center for Arboviruses, Department of Microbiology, School of Medicine, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece; E-mail:
| | - George Valiakos
- Laboratory of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (G.V); (A.G.); (K.P.); (C.B.)
| | - Serafeim C. Chaintoutis
- Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece; E-mails: (S.C.C.); (C.I.D.)
| | - Dimitrios Doukas
- Laboratory of Pathology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (D.D.); (D.T.)
| | - Persefoni Tserkezou
- Department of Microbiology, Faculty of Medicine, University of Athens, Athens 11527, Greece; E-mail:
| | - Alexios Giannakopoulos
- Laboratory of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (G.V); (A.G.); (K.P.); (C.B.)
| | - Konstantinos Papaspyropoulos
- Laboratory of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (G.V); (A.G.); (K.P.); (C.B.)
| | - Eleni Patsoula
- Department of Parasitology, Entomology and Tropical Diseases, National School of Public Health, Athens 11521, Greece; E-mail:
| | - Evangelos Badieritakis
- Laboratory of Biological Control of Pesticides, Benaki Phytopathological Institute, Athens 14561, Greece; E-mails: (E.B.); (G.K.)
| | - Agoritsa Baka
- Hellenic Centre for Disease Control and Prevention (KEELPNO), Athens 15123, Greece; E-mails: (A.B.); (M.T.); (D.P.); (J.K.)
| | - Maria Tseroni
- Hellenic Centre for Disease Control and Prevention (KEELPNO), Athens 15123, Greece; E-mails: (A.B.); (M.T.); (D.P.); (J.K.)
| | - Danai Pervanidou
- Hellenic Centre for Disease Control and Prevention (KEELPNO), Athens 15123, Greece; E-mails: (A.B.); (M.T.); (D.P.); (J.K.)
| | - Nikos T. Papadopoulos
- Laboratory of Entomology and Agricultural Zoology, School of Agricultural Sciences, University of Thessaly, Volos 38446, Greece; E-mails: (A.D.); (N.T.P.)
| | - George Koliopoulos
- Laboratory of Biological Control of Pesticides, Benaki Phytopathological Institute, Athens 14561, Greece; E-mails: (E.B.); (G.K.)
| | - Dimitrios Tontis
- Laboratory of Pathology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (D.D.); (D.T.)
| | - Chrysostomos I. Dovas
- Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece; E-mails: (S.C.C.); (C.I.D.)
| | - Charalambos Billinis
- Laboratory of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Thessaly, Karditsa 43100, Greece; E-mails: (G.V); (A.G.); (K.P.); (C.B.)
| | - Athanassios Tsakris
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +30-2410-565-007; Fax: +30-2410-565-051
| | - Jenny Kremastinou
- Hellenic Centre for Disease Control and Prevention (KEELPNO), Athens 15123, Greece; E-mails: (A.B.); (M.T.); (D.P.); (J.K.)
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Hartley DM, Barker CM, Le Menach A, Niu T, Gaff HD, Reisen WK. Effects of temperature on emergence and seasonality of West Nile virus in California. Am J Trop Med Hyg 2012; 86:884-94. [PMID: 22556092 PMCID: PMC3335698 DOI: 10.4269/ajtmh.2012.11-0342] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 02/04/2012] [Indexed: 11/07/2022] Open
Abstract
Temperature has played a critical role in the spatiotemporal dynamics of West Nile virus transmission throughout California from its introduction in 2003 through establishment by 2009. We compared two novel mechanistic measures of transmission risk, the temperature-dependent ratio of virus extrinsic incubation period to the mosquito gonotrophic period (BT), and the fundamental reproductive ratio (R(0)) based on a mathematical model, to analyze spatiotemporal patterns of receptivity to viral amplification. Maps of BT and R(0) were created at 20-km scale and compared throughout California to seroconversions in sentinel chicken flocks at half-month intervals. Overall, estimates of BT and R(0) agreed with intensity of transmission measured by the frequency of sentinel chicken seroconversions. Mechanistic measures such as these are important for understanding how temperature affects the spatiotemporal dynamics of West Nile virus transmission and for delineating risk estimates useful to inform vector control agency intervention decisions and communicate outbreak potential.
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Affiliation(s)
- David M Hartley
- Georgetown University Medical Center, Washington, District of Columbia 20057, USA.
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Pangloss revisited: a critique of the dilution effect and the biodiversity-buffers-disease paradigm. Parasitology 2012; 139:847-63. [PMID: 22336330 DOI: 10.1017/s0031182012000200] [Citation(s) in RCA: 254] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The twin concepts of zooprophylaxis and the dilution effect originated with vector-borne diseases (malaria), were driven forward by studies on Lyme borreliosis and have now developed into the mantra "biodiversity protects against disease". The basic idea is that by diluting the assemblage of transmission-competent hosts with non-competent hosts, the probability of vectors feeding on transmission-competent hosts is reduced and so the abundance of infected vectors is lowered. The same principle has recently been applied to other infectious disease systems--tick-borne, insect-borne, indirectly transmitted via intermediate hosts, directly transmitted. It is claimed that the presence of extra species of various sorts, acting through a variety of distinct mechanisms, causes the prevalence of infectious agents to decrease. Examination of the theoretical and empirical evidence for this hypothesis reveals that it applies only in certain circumstances even amongst tick-borne diseases, and even less often if considering the correct metric--abundance rather than prevalence of infected vectors. Whether dilution or amplification occurs depends more on specific community composition than on biodiversity per se. We warn against raising a straw man, an untenable argument easily dismantled and dismissed. The intrinsic value of protecting biodiversity and ecosystem function outweighs this questionable utilitarian justification.
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Chevalier V, Lecollinet S, Durand B. West Nile Virus in Europe: A Comparison of Surveillance System Designs in a Changing Epidemiological Context. Vector Borne Zoonotic Dis 2011; 11:1085-91. [DOI: 10.1089/vbz.2010.0234] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Veronique Chevalier
- International Centre of Research in Agronomy for Development (CIRAD), Montpellier, France
| | - Sylvie Lecollinet
- European Union Reference Laboratory for Equine Diseases, Virology Unit, Maisons-Alfort, France
- Agence Nationale de Sécurité Sanitaire (ANSES), Laboratoire de Santé Animale, Maisons-Alfort, France
| | - Benoit Durand
- Agence Nationale de Sécurité Sanitaire (ANSES), Laboratoire de Santé Animale, Maisons-Alfort, France
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Magori K, Bajwa WI, Bowden S, Drake JM. Decelerating spread of West Nile virus by percolation in a heterogeneous urban landscape. PLoS Comput Biol 2011; 7:e1002104. [PMID: 21829332 PMCID: PMC3145642 DOI: 10.1371/journal.pcbi.1002104] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 05/12/2011] [Indexed: 01/05/2023] Open
Abstract
Vector-borne diseases are emerging and re-emerging in urban environments throughout the world, presenting an increasing challenge to human health and a major obstacle to development. Currently, more than half of the global population is concentrated in urban environments, which are highly heterogeneous in the extent, degree, and distribution of environmental modifications. Because the prevalence of vector-borne pathogens is so closely coupled to the ecologies of vector and host species, this heterogeneity has the potential to significantly alter the dynamical systems through which pathogens propagate, and also thereby affect the epidemiological patterns of disease at multiple spatial scales. One such pattern is the speed of spread. Whereas standard models hold that pathogens spread as waves with constant or increasing speed, we hypothesized that heterogeneity in urban environments would cause decelerating travelling waves in incipient epidemics. To test this hypothesis, we analysed data on the spread of West Nile virus (WNV) in New York City (NYC), the 1999 epicentre of the North American pandemic, during annual epizootics from 2000–2008. These data show evidence of deceleration in all years studied, consistent with our hypothesis. To further explain these patterns, we developed a spatial model for vector-borne disease transmission in a heterogeneous environment. An emergent property of this model is that deceleration occurs only in the vicinity of a critical point. Geostatistical analysis suggests that NYC may be on the edge of this criticality. Together, these analyses provide the first evidence for the endogenous generation of decelerating travelling waves in an emerging infectious disease. Since the reported deceleration results from the heterogeneity of the environment through which the pathogen percolates, our findings suggest that targeting control at key sites could efficiently prevent pathogen spread to remote susceptible areas or even halt epidemics. Current theory of the spatial spread of pathogens predicts travelling waves at constant or increasing speed in homogeneous environments. However, in urban environments, increasing and often unregulated development produces a highly heterogeneous landscape. Such heterogeneity affects pathogens spread by insect vectors particularly, which typically have short dispersal distances. We hypothesized that high levels of heterogeneity can slow the spread of such pathogens, resulting in decelerating epidemic waves. We analysed the annual spread of West Nile virus (WNV) in New York City (NYC), using a dataset containing >1,000,000 records since the origin of the North American pandemic in 1999. Our analysis provides the first evidence of endogenous decelerating travelling waves in an emerging infectious disease. We found that WNV spread with decreasing speed in each season and rejected four alternative hypotheses to explain this deceleration. A mathematical model shows that high levels of heterogeneity can lead to such decelerating travelling waves. Interestingly, the level of heterogeneity in land-cover types associated with WNV-positive dead birds in NYC is of the order of magnitude required to produce decelerating travelling waves in the model. Consequently, we propose that control strategies targeting key sites may be effective at slowing WNV spread in NYC.
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Affiliation(s)
- Krisztian Magori
- Odum School of Ecology, University of Georgia, Athens, Georgia, United States of America.
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Brown CR, O'Brien VA. Are Wild Birds Important in the Transport of Arthropod-borne Viruses? ACTA ACUST UNITED AC 2011. [DOI: 10.1525/om.2011.71.1.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Fall AG, Diaïté A, Lancelot R, Tran A, Soti V, Etter E, Konaté L, Faye O, Bouyer J. Feeding behaviour of potential vectors of West Nile virus in Senegal. Parasit Vectors 2011; 4:99. [PMID: 21651763 PMCID: PMC3118230 DOI: 10.1186/1756-3305-4-99] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 06/08/2011] [Indexed: 11/10/2022] Open
Abstract
Background West Nile virus (WNV) is a widespread pathogen maintained in an enzootic cycle between mosquitoes and birds with occasional spill-over into dead-end hosts such as horses and humans. Migratory birds are believed to play an important role in its dissemination from and to the Palaearctic area, as well as its local dispersion between wintering sites. The Djoudj Park, located in Senegal, is a major wintering site for birds migrating from Europe during the study period (Sept. 2008- Jan. 2009). In this work, we studied the seasonal feeding behaviour dynamics of the potential WNV mosquito vectors at the border of the Djoudj Park, using a reference trapping method (CDC light CO2-baited traps) and two host-specific methods (horse- and pigeon-baited traps). Blood meals of engorged females were analysed to determine their origin. Results Results indicated that Culex tritaeniorhynchus and Cx. neavei may play a key role in the WNV transmission dynamics, the latter being the best candidate bridging-vector species between mammals and birds. Moreover, the attractiveness of pigeon- and horse-baited traps for Cx. neavei and Cx. tritaeniorhynchus varied with time. Finally, Cx. tritaeniorhynchus was only active when the night temperature was above 20°C, whereas Cx. neavei was active throughout the observation period. Conclusions Cx. neavei and Cx. tritaeniorhynchus are the main candidate vectors for the transmission of WNV in the area. The changes in host attractiveness might be related to variable densities of the migratory birds during the trapping period. We discuss the importance of these results on the risk of WNV transmission in horses and humans.
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Affiliation(s)
- Assane G Fall
- Institut Sénégalais de Recherches Agricoles/Laboratoire National de l'Elevage et de Recherches Vétérinaires, BP 2057 Dakar-Hann, Sénégal.
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31
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O'Brien VA, Meteyer CU, Reisen WK, Ip HS, Brown CR. Prevalence and pathology of West Nile virus in naturally infected house sparrows, western Nebraska, 2008. Am J Trop Med Hyg 2010; 82:937-44. [PMID: 20439979 DOI: 10.4269/ajtmh.2010.09-0515] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Nestling birds are rarely sampled in the field for most arboviruses, yet they may be important in arbovirus amplification cycles. We sampled both nestling and adult house sparrows (Passer domesticus) in western Nebraska for West Nile virus (WNV) or WNV-specific antibodies throughout the summer of 2008 and describe pathology in naturally infected nestlings. Across the summer, 4% of nestling house sparrows were WNV-positive; for the month of August alone, 12.3% were positive. Two WNV-positive nestlings exhibited encephalitis, splenomegaly, hepatic necrosis, nephrosis, and myocarditis. One nestling sparrow had large mural thrombi in the atria and ventricle and immunohistochemical staining of WNV antigen in multiple organs including the wall of the aorta and pulmonary artery; cardiac insufficiency thus may have been a cause of death. Adult house sparrows showed an overall seroprevalence of 13.8% that did not change significantly across the summer months. The WNV-positive nestlings and the majority of seropositive adults were detected within separate spatial clusters. Nestling birds, especially those reared late in the summer when WNV activity is typically greatest, may be important in virus amplification.
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Affiliation(s)
- Valerie A O'Brien
- Department of Biological Sciences, University of Tulsa, Tulsa, Oklahoma, USA.
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Ecological determinants of American crow mortality due to West Nile virus during its North American sweep. Oecologia 2010; 163:903-9. [PMID: 20425125 DOI: 10.1007/s00442-010-1627-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 03/26/2010] [Indexed: 11/27/2022]
Abstract
We examined the ecological factors influencing population declines in American crows (Corvus brachyrhynchos) as they were initially exposed to West Nile virus (WNV), a pathogen first detected in the US in 1999 that has since become one of North America's most prevalent vector-borne pathogens. The strongest effects were initial crow population density (denser populations were more likely to suffer declines), avian species diversity (populations in areas with high diversity were less likely to suffer a decline), human population density (populations were more likely to decline in more urban areas), and time since the pathogen's introduction to the US (populations exposed to the pathogen later in its North American sweep were less likely to suffer declines than those exposed earlier). Variables that played only a minor role included rainfall, mean maximum temperature, and total number of birds, used as a proxy for the overall reservoir competence of the community. These findings indicate that WNV declined in virulence during its rapid 5-year sweep and support the importance of the 'dilution effect' whereby a diverse host community dampens pathogen transmission and potentially slows its rate of spread. Results underscore the need for considering the entire community when trying to understand the factors shaping disease risk.
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Environmental risk factors of West Nile virus infection of horses in the Senegal River basin. Epidemiol Infect 2010; 138:1601-9. [PMID: 20175940 DOI: 10.1017/s095026881000035x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In 2005, a serological study was carried out on horses in five ecologically contrasted zones of the Senegal River basin (Senegal) to assess West Nile virus (WNV) transmission and investigate underlying environmental risk factors. In each study zone, horses were randomly selected and blood samples taken. A land-cover map of the five study areas was built using two satellite ETM+ images. Blood samples were screened by ELISA for anti-WNV IgM and IgG and positive samples were confirmed by seroneutralization. Environmental data were analysed using a principal components analysis. The overall IgG seroprevalence rate was 85% (n=367; 95% CI 0.81-0.89). The proximity to sea water, flooded banks and salted mudflats were identified as protective factors. These environmental components are unfavourable to the presence of Culex mosquitoes suggesting that in Senegal, the distribution of the vector species is more limiting for WNV transmission than for the hosts' distribution.
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Durand B, Balança G, Baldet T, Chevalier V. A metapopulation model to simulate West Nile virus circulation in Western Africa, Southern Europe and the Mediterranean basin. Vet Res 2010; 41:32. [PMID: 20167194 PMCID: PMC2826092 DOI: 10.1051/vetres/2010004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 01/13/2010] [Indexed: 11/14/2022] Open
Abstract
In Europe, virological and epidemiological data collected in wild birds and horses suggest that a recurrent circulation of West Nile virus (WNV) could exist in some areas. Whether this circulation is permanent (due to overwintering mechanisms) or not remains unknown. The current conception of WNV epidemiology suggests that it is not: this conception combines an enzootic WNV circulation in tropical Africa with seasonal introductions of the virus in Europe by migratory birds. The objectives of this work were to (i) model this conception of WNV global circulation; and (ii) evaluate whether the model could reproduce data and patterns observed in Europe and Africa in vectors, horses, and birds. The model was calibrated using published seroprevalence data obtained from African (Senegal) and European (Spain) wild birds, and validated using independent, published data: seroprevalence rates in migratory and resident wild birds, minimal infection rates in vectors, as well as seroprevalence and incidence rates in horses. According to this model, overwintering mechanisms are not needed to reproduce the observed data. However, the existence of such mechanisms cannot be ruled out.
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Affiliation(s)
- Benoit Durand
- Afssa LERPAZ, 23 Avenue du Général de Gaulle, 94706 Maisons-Alfort Cedex, France.
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35
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Smith A. Infection prevalence and vector-borne transmission: are vectors always to blame? Trends Parasitol 2008; 24:492-6. [DOI: 10.1016/j.pt.2008.07.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Revised: 07/29/2008] [Accepted: 07/31/2008] [Indexed: 10/21/2022]
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