An epidemiologic and serologic study of arboviruses in Lake Rudolf basin.

An epidemiologic and serologic study of arboviruses was done in 1972 in the basin of Lake Rudolf. The main object of this study was to demarcate the southern limit of the yellow fever epidemic which occurred from 1959 to 1962 in Southern Sudan and Ethiopia. Other purposes were to contribute to the inventory of arboviruses and their distribution in this region. The ethnic groups were studied: the Nyangatom and the Dassanetch in Ethiopia and the Turkana in northern Kenya. The results of tests on sera of the Nyangatom and the Dassanetch are practically identical: a high percentage of positive tests for group B. The Turkana on the other hand show a low percentage of positives. This is attributed to differences in the climatic characteristics of the two regions. The serological results suggest the presence of West Nile virus in the geographical areas inhabited by the three ethnic groups. The presence of Wesselsbron and probably Uganda S virus is suspected. Circulation of these viruses could be explained by the presence of Culex univittatus and other mosquitoes. As for yellow fever, the results suggest that the virus did not reach the areas studied, probably because of absence of efficient vectors.