DENGUE, ARBOVIRUSES AND MIGRATIONS IN THE INDIAN-OCEAN

An arbovirus requires a competent haematophagous arthropod for transmi ssion from one vertebrate to another susceptible host. Air transportat ions allow quick transfers from place to place and the diffusion of po tential vectors or infectious hosts. The merchandise transportation by containers allowed the diffusion of Ae. albopictus from Asia through Africa and America. Emerging arbovirosis may occur in zones where they do not exist Dengue which originally was located in southeastern Asia , is the most important arbovirosis in the world. The occurrence of de ngue haemorrhagic fever (DHF) in Asia and America, mostly in urban are as, increased the global concern about dengue. Likewise, cases of DHF are not reported in Africa and in the Indian Ocean southwestern island s. The principal vector of dengue, Aedes aegypti, was present during t he dengue 1 outbreak in Comoros, in 1993. In the other islands, only f ew specimens of Ae. aegypti are observed, and described mostly as none anthropophilic forms. The role of Ae. albopictus as vector of dengue was suspected and reported during outbreaks in Seychelles and Reunion island in 1977-1978. Yellow fever, present in Africa mostly in restric ted areas, is absent in Asia. Japanese encephalitis considered as an e merging disease in India could expand through the islands. Rift valley fever; with periodic epizootics in domestic ungulates in Africa, was described as a new disease in Madagascar in 1990-1991. Crimean-Congo h aemorrhagic fever is also present in Madagascar Humans can be infected by vector bite or by handling infectious animal products. The distrib ution of other viruses (West Nile, Sindbis, Wesselsbron or Chikungunya ) is discussed.