Genetic epidemiology of host predisposition microfilaraemia in human loiasis

Evidence is accumulating from experimental and human studies that genetic f actors ate involved both in the control of infectious diseases and in the r egulation of infection levels and clinical presentation. So far few studies have investigated the role of these genetic factors in human infection by the filarial parasite Loa loa. We present a segregation analysis on 74 nucl ear families who live in the tropical rainforest of southern Cameroun and a re exposed to humogeneous loiasis transmission, The results indicate that t here is a generic predisposition to be microfilaraemic and that predisposed subjects might be genetically unable to mount an efficient immune response against loiasis antigens. This individual susceptibility could explain at least in part why the prevalence of infection (microfilaraemic individuals) does nor usually exceed 30% of the exposed population in hyperendemic regi ons. Further genetic studies, based on linkage analysis using both familial information and generic markers, will help to identify the nature of the g enetic factors predisposing to microfilaraemia.