LONGITUDINAL SURVEY OF LOA LOA FILARIASIS IN SOUTHERN CAMEROON - LONG-TERM STABILITY AND FACTORS INFLUENCING INDIVIDUAL MICROFILARIAL STATUS

A longitudinal, one-year survey of Loa loa infection was carried out i n an endemic area of southern Cameroon. Parasitologic samplings (calib rated thick blood smears) were performed every two months to study the evolution of loiasis infection at both the population and the individ ual level. The mean number of measurements by subject was 3.8 (range 1 -6). At the population level, prevalence of infection and microfilaria l load were found to be very stable over time. This observation is con sistent with the existence of an important reserve of parasitic materi al available for vectors and the maintenance of high levels of transmi ssion. At the individual level, both the microfilarial status (microfi laremic/nonmicrofilaremic) and the level of parasitemia showed a remar kable stability over time. Age was the relevant factor that influenced the individual microfilarial status in the whole population. When onl y microfilaremic individuals were taken into account, age did not infl uence the level of microfilaremia, suggesting that loiasis could be co nsidered as a noncumulative disease. The stability of individual micro filarial status and the pattern of infection variations observed with age support the view that genetic factors might be involved in host de fense mechanisms against loiasis infection.