Factors Associated with Microfilaremia in an Endemic Area of Mali

Although (), the causative agent of lymphatic filariasis, is endemic throughout Mali, the prevalence of microfilaremia (Mf) can vary widely between villages despite similar prevalence of infection as assessed by circulating antigen. To examine this variation, cross-sectional data obtained during screening prior to an interventional study in two neighboring villages in Mali were analyzed. The overall prevalence of , as assessed by CAg (circulating antigen), was 50.3% among 373 participants, aged 14-65. Mf-positive and negative individuals appeared randomly distributed across the two villages (Moran's I spatial statistic = -0.01, Z score =0.1, P>0.05). Among the 187 subjects positive for CAg, 117 (62.5%) had detectable microfilaremia ( Mf) and 64 (34.2%) had detectable microfilaremia. The prevalence of microfilaremia was 73.4% in the Mf-positive group (as compared to 56.9% in the Mf-negative group; p=0.01), and median Mf load was increased in co-infected subjects (267Mf/ml vs 100 Mf/ml; p<0.001). In multivariate analysis, village of residence, Mf positivity and gender were significantly associated with Mf positivity. After controlling for age, gender, and village of residence, the odds of being Mf positive was 2.67 times higher in positive individuals (95% confidence interval [1.42-5.01]). Given the geographical overlap between and in Africa, a better understanding of the distribution and prevalence of could assist national lymphatic filariasis control programs in predicting areas of high Mf prevalence that may require closer surveillance.