[Transmission cycles of the West-Nile virus in Madagascar, Indian Ocean].

Virological, serological and entomological research conducted in Madagascar since 1975, reveal the wide-spread presence of West-Nile virus on the island. This arbovirus has been isolated from humans, parrots and egrets. Vectors belong to the genus Culex (e.g. Cx. decens, Cx. quinquefasciatus, Cx. antennatus, Cx. univittatus), however the virus has also been isolated from Aedes and Anopheles. Serological tests carried out on over 1,600 human and almost 1,000 animal sera, revealed that human beings could be infected throughout the island. Other potential vertebrate hosts, apart from birds, are oxen and bats. Insectivores, rodents and lemurs are probably involved in the transmission cycles only to a very small extent.