Abstract
West Nile virus is an arthropod-borne zoonosis transmitted by a large number of mosquito species, and birds play a key role as reservoir of the virus. Its distribution is largely widespread over Africa, Asia, the Americas and Europe. Since 1978, it has frequently been reported in Madagascar. Studies described a high seroprevalence level of the virus in humans in different areas of the island and a human fatal case of WNV infection was reported in 2011. Despite these reports, the epidemiology of WNV in Madagascar, in particular, viral circulation remains unclear. To explore the transmission of WNV in two rural human populations of Madagascar, we investigated local mosquitoes and poultry for evidence of current infections, and determined seroprevalence of candidate sentinel species among the local poultry. These 2 areas are close to lakes where domestic birds, migratory wild birds and humans coexist. Serological analysis revealed WNV antibodies in domestic birds (duck, chicken, goose, turkey and guinea fowl) sampled in both districts (Antsalova 29.4% and Mitsinjo 16.7%). West Nile virus nucleic acid was detected in one chicken and in 8 pools of mosquitoes including 2 mosquito species (Aedeomyia madagascarica and Anopheles pauliani) that have not been previously described as candidate vectors for WNV. Molecular analysis of WNV isolates showed that all viruses detected were part of the lineage 2 that is mainly distributed in Africa, and were most closely matched by the previous Malagasy strains isolated in 1988. Our study showed that WNV circulates in Madagascar amongst domestic birds and mosquitoes, and highlights the utility of poultry as a surveillance tool to detect WNV transmission in a peri-domestic setting.
Highlights
West Nile virus (WNV) is a zoonotic arbovirus affecting humans, horses and wildlife
Our results confirm domestic poultry are exposed to WNV in Madagascar and describe two new mosquito species as potential vector for WNV
Viral RNA was identified in 4 mosquito species (Anopheles coustani, Anopheles pauliani, Mansonia uniformis, and Aedeomyia madagascarica)
Summary
West Nile virus (WNV) is a zoonotic arbovirus affecting humans, horses and wildlife. The virus is widely distributed in Africa, Asia and Europe and spread over the last 2 decades to North and South America [1]. Like American crow (Corvus brachyrhynchos) and house sparrow (Passer domesticus) develop a sufficient viremia titer to transmit the virus to mosquitoes, while others like the domestic rock pigeon (Columba livia) and the barn owl (Tyto alba) do not [7, 8]. These birds are considered as amplifiers with a key role in the epidemiology of the virus and can as act reservoirs. Poultry species have been used as surveillance sentinels in many geographic regions [9] but their role of WNV transmission and surveillance value has not been well-investigated at this time
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