Factors Associated with Wuchereria bancrofti Microfilaremia in an Endemic Area of Mali

Although Wuchereria bancrofti (Wb), the causative agent of lymphatic filariasis, is endemic throughout Mali, the prevalence of Wb 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 Wb, as assessed by Wb Cag (circulating antigen), was 50.3% among 373 participants, aged 14-65. Wb 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 Wb CAg, 117 (62.5%) had detectable Mansonella perstans microfilaremia (Mp Mf) and 64(34.2%) had detectable Wb microfilaremia. The prevalence of Mp microfilaremia was 73.4% in the Wb Mf-positive group (as compared to 56.9% in the Wb Mf-negative group; p=0.01), and median Wb Mf load was increased in co-infected subjects (267 Mf/ml vs 100 Mf/ml; p < 0.001). In multivariate analysis, village of residence, Mp Mf positivity and gender were significantly associated with Wb Mf positivity. After controlling for age, gender and village of residence, the odds of being Wb Mf positive was 2.67 times higher in Mp positive individuals (95% CI [1.42-5.01]). Given the geographical overlap between Mp and Wb in Africa, a better understanding of the distribution and prevalence of Mp could assist national LF control programs in predicting areas of high Wb mf prevalence that may require closer surveillance.