Modelling vaccination strategies against Rift Valley fever in livestock in Kenya
Background The impacts of vaccination on the transmission of Rift Valley fever virus (RVFV) have not been evaluated. We have developed a RVFV transmission model comprising two hosts—cattle as a separate host and sheep and goats as one combined host (herein after referred to as sheep)—and two vectors...
| Autores principales: | , , , |
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| Formato: | Journal Article |
| Lenguaje: | Inglés |
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Public Library of Science
2016
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| Materias: | |
| Acceso en línea: | https://hdl.handle.net/10568/78660 |
| _version_ | 1855543276683132928 |
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| author | Gachohi, John M. Njenga, M.K. Kitala, P. Bett, Bernard K. |
| author_browse | Bett, Bernard K. Gachohi, John M. Kitala, P. Njenga, M.K. |
| author_facet | Gachohi, John M. Njenga, M.K. Kitala, P. Bett, Bernard K. |
| author_sort | Gachohi, John M. |
| collection | Repository of Agricultural Research Outputs (CGSpace) |
| description | Background The impacts of vaccination on the transmission of Rift Valley fever virus (RVFV) have not been evaluated. We have developed a RVFV transmission model comprising two hosts—cattle as a separate host and sheep and goats as one combined host (herein after referred to as sheep)—and two vectors—Aedes species (spp) and Culex spp—and used it to predict the impacts of: (1) reactive vaccination implemented at various levels of coverage at pre-determined time points, (2) targeted vaccination involving either of the two host species, and (3) a periodic vaccination implemented biannually or annually before an outbreak. Methodology/Principal Findings The model comprises coupled vector and host modules where the dynamics of vectors and hosts are described using a system of difference equations. Vector populations are structured into egg, larva, pupa and adult stages and the latter stage is further categorized into three infection categories: susceptible, exposed and infectious mosquitoes. The survival rates of the immature stages (egg, larva and pupa) are dependent on rainfall densities extracted from the Tropical Rainfall Measuring Mission (TRMM) for a Rift Valley fever (RVF) endemic site in Kenya over a period of 1827 days. The host populations are structured into four age classes comprising young, weaners, yearlings and adults and four infection categories including susceptible, exposed, infectious, and immune categories. The model reproduces the 2006/2007 RVF outbreak reported in empirical surveys in the target area and other seasonal transmission events that are perceived to occur during the wet seasons. Mass reactive vaccination strategies greatly reduce the potential for a major outbreak. The results also suggest that the effectiveness of vaccination can be enhanced by increasing the vaccination coverage, targeting vaccination on cattle given that this species plays a major role in the transmission of the virus, and using both periodic and reactive vaccination strategies. Conclusion/Significance Reactive vaccination can be effective in mitigating the impacts of RVF outbreaks but practically, it is not always possible to have this measure implemented satisfactorily due to the rapid onset and evolution of RVF epidemics. This analysis demonstrates that both periodic and reactive vaccination ought to be used strategically to effectively control the disease. |
| format | Journal Article |
| id | CGSpace78660 |
| institution | CGIAR Consortium |
| language | Inglés |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Public Library of Science |
| publisherStr | Public Library of Science |
| record_format | dspace |
| spelling | CGSpace786602023-12-08T19:36:04Z Modelling vaccination strategies against Rift Valley fever in livestock in Kenya Gachohi, John M. Njenga, M.K. Kitala, P. Bett, Bernard K. animal diseases disease control livestock zoonoses Background The impacts of vaccination on the transmission of Rift Valley fever virus (RVFV) have not been evaluated. We have developed a RVFV transmission model comprising two hosts—cattle as a separate host and sheep and goats as one combined host (herein after referred to as sheep)—and two vectors—Aedes species (spp) and Culex spp—and used it to predict the impacts of: (1) reactive vaccination implemented at various levels of coverage at pre-determined time points, (2) targeted vaccination involving either of the two host species, and (3) a periodic vaccination implemented biannually or annually before an outbreak. Methodology/Principal Findings The model comprises coupled vector and host modules where the dynamics of vectors and hosts are described using a system of difference equations. Vector populations are structured into egg, larva, pupa and adult stages and the latter stage is further categorized into three infection categories: susceptible, exposed and infectious mosquitoes. The survival rates of the immature stages (egg, larva and pupa) are dependent on rainfall densities extracted from the Tropical Rainfall Measuring Mission (TRMM) for a Rift Valley fever (RVF) endemic site in Kenya over a period of 1827 days. The host populations are structured into four age classes comprising young, weaners, yearlings and adults and four infection categories including susceptible, exposed, infectious, and immune categories. The model reproduces the 2006/2007 RVF outbreak reported in empirical surveys in the target area and other seasonal transmission events that are perceived to occur during the wet seasons. Mass reactive vaccination strategies greatly reduce the potential for a major outbreak. The results also suggest that the effectiveness of vaccination can be enhanced by increasing the vaccination coverage, targeting vaccination on cattle given that this species plays a major role in the transmission of the virus, and using both periodic and reactive vaccination strategies. Conclusion/Significance Reactive vaccination can be effective in mitigating the impacts of RVF outbreaks but practically, it is not always possible to have this measure implemented satisfactorily due to the rapid onset and evolution of RVF epidemics. This analysis demonstrates that both periodic and reactive vaccination ought to be used strategically to effectively control the disease. 2016-12-14 2017-01-10T14:09:18Z 2017-01-10T14:09:18Z Journal Article https://hdl.handle.net/10568/78660 en Open Access Public Library of Science Gachohi, J.M., Njenga, M.K., Kitala, P. and Bett, B. 2016. Modelling vaccination strategies against Rift Valley fever in livestock in Kenya. PLOS Neglected Tropical Diseases 10(12): e0005049. |
| spellingShingle | animal diseases disease control livestock zoonoses Gachohi, John M. Njenga, M.K. Kitala, P. Bett, Bernard K. Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title | Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title_full | Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title_fullStr | Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title_full_unstemmed | Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title_short | Modelling vaccination strategies against Rift Valley fever in livestock in Kenya |
| title_sort | modelling vaccination strategies against rift valley fever in livestock in kenya |
| topic | animal diseases disease control livestock zoonoses |
| url | https://hdl.handle.net/10568/78660 |
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