Avian and equine surveillance for two flaviviruses in Burkina Faso: Usutu virus and West Nile virus

" Background and rationale: For several years, Burkina Faso has been facing the emergence and re-emergence of arboviruses, causing epidemics and deaths. Despite the existence of a surveillance system for these arboviruses, some, such as USUV and WNV, are not covered by it. West Nile virus (WNV) and Usutu virus (USUV) are phylogenetically related arboviruses transmitted mainly by mosquitoes of the Culex genus. Birds are the main amplifying hosts, and humans and horses are accidental hosts. It is difficult to predict when these pathogens can pass from animal to human, hence the importance of monitoring the animal reservoirs involved in the enzootic cycle of these virsus. Avian surveillance of USUV and WNV would make it possible to identify the species involved in the amplification and circulation of these viruses in Burkina Faso, and to anticipate the occurrence of human epidemics. Objective: The aim of this study is to conduct molecular and serological surveillance of USUV and WNV in domestic and wild birds and horses in urban and semi-urban areas of Burkina Faso, taking into account seasonal variations. Methods: This will be a descriptive, prospective, cross-sectional study conducted over 3 years in urban (Bobo-Dioulasso) and semi-urban (Banfora) areas. Samples will be collected taking into account seasonal variations, to see the dynamics of arbovirus circulation as a function of the seasons. Blood samples will be taken from horses. In birds, a blood drop will be taken on blotting paper, along with an oral or rectal swab. Organ samples will also beIn birds, a blood drop will be taken on blotting paper, along with an oral or rectal swab. Organ samples will also be taken from birds found dead. A total of 385 samples from domestic birds, wild birds and horses will be collected. All samples collected will be transported to the host laboratory in Montpellier for molecular and serological analysis. On the molecular level, all samples will be analyzed by RT-PCR for the detection of RNA of the viruses of interest, and positive samples will be sequenced and phylogenetically analyzed to identify circulating virus strains. On the serological front, samples will first be screened by a commercial Pan-Flavivirus ELISA, and positive samples will then be tested by serum neutralisation to detect virus-specific antibodies. Expected results: The results of our work will enable us to identify the avian species involved in maintaining the enzootic cycle of USUV and WNV in Burkina Faso, as well as the seasons of high circulation of these viruses. At the end of our work, we will have information on circulating viral strains. The study on horses will enable us to validate the relevance of using them as sentinels in the surveillance of these flaviviruses. We will then be able to make concrete proposals to the relevant authorities in Burkina Faso to improve the surveillance and control of these viruses. Schedule: Setting up and obtaining administrative authorizations and consents will take place during the first five months of the first year; sample acquisition from the sixth to the ninth month of the first year and the first nine months of the second year; Laboratory analysis from the tenth month of the first year until the end of the third year; data analysis from the first month of the second year until the end of the third year; data valorization from the seventh month of the second year until the end of the third year."