[Ecology of tick-borne arboviruses in the Central African Republic]

Ticks have been collected on cattle skins for seven consecutive years in Bangui, Berberati, Bangassou and Bouar. 150 strains of arboviruses have been isolated from the four following species: Amblyomma variegatum: Dugbe, Jos, Thogoto, Crimean-Congo Hemorragic Fever (CCHF), Yellow Fever, Bhanja and Pétévo; Boophilus annulatus: Dugbe, Jos and Thogoto; B. decoloratus: Dugbe, Jos, Thogoto and CCHF; Hyalomma nitidum: CCHF. Dugbe (112 isolated strains), Jos (19 isolates) and Thogoto (11 isolates) viruses represent more than 95% of all the strains. Dugbe virus was isolated mostly during the first half of the rainy season. Jos virus shows a maximum rate of infection during the dry season (february) and a second peak in october (2nd half of the rainy season). Most of the strains of Thogoto virus have been isolated during the dry season. These seasonal variations of infection rates follow the seasonal variation of vector population densities. Thus preimagines and imagines of A. variegatum, the main vector of the Dugbe virus in C. A. R. show peaks of abundance respectively during the dry season and during the first half of the rainy season. Adults of Boophilus show maximum densities from december to february (dry season) when the greater number of Jos and Thogoto viruses are isolated. CCHF virus ecology needs more studies in Central African Republic. The importance of ticks in the wild cycle of Yellow Fever virus is not yet understood. Bhanja virus has been isolated only one time in C. A. R. Pétévo is a lately described virus which belongs to a group thus far unknown in Africa (Palyam gr.).