THE CULICOIDES VECTORS OF AFRICAN HORSE SICKNESS VIRUS IN MOROCCO - DISTRIBUTION AND EPIDEMIOLOGIC IMPLICATIONS

African horse sickness (AHS) is a vector-borne, infectious disease of equids caused by African horse sickness virus. The only proven field v ector of the virus is the biting midge Culicoides imicola, although C. obsoletus and C. pulicaris are suspected vectors. In 1994-5 a total o f 3887 light trap samples were collected from 22 sites distributed ove r most of Morocco. Culicoides imicola was found to be very widely dist ributed with the greatest catches in the low-lying north-western areas (between Tangier and Rabat) and at Marrakech. Culicoides imicola was absent at one site only, near Settat. In general, the catch of C. imic ola peaked in late summer and autumn, with a smaller peak in spring. C atches of C. obsoletus were greatest in the north-western provinces of Morocco and in the south, while catches of C. pulicaris were greatest in the north. Although both species were widely distributed, trap cat ches were much lower than those of C. imicola. Peak catches were in sp ring or late summer and autumn. In general, the findings for C. imicol a correspond well with the seasonal and spatial distribution of diseas e outbreaks during the 1989-1991 epizootic of AHS in Morocco. It is su ggested that C. obsoletus and C. pulicaris were probably of little sig nificance in the epidemiology of AHS in Morocco in 1989-91.