Risk factors for lymphatic filariasis in two villages of the Democratic Republic of the Congo

BACKGROUND: Little is known regarding risk factors for lymphatic filariasis (LF) in Central Africa. To expand on what is known, we studied the epidemiology of LF in two endemic villages in the Democratic Republic of the Congo. METHODS: Dependent variables were Wuchereria bancrofti antigenaemia detected with filarial test strips (FTS) and microfilaraemia detected by night blood smears. The following factors were investigated: sex, age, the use of bednets, the use of latrines, hunting, fishing and agricultural activities, history of treatment with anthelmintic drugs, overnight stays in the bush, population density, the number of household members, and distance to rivers. Mixed multivariate logistic regression models were used. RESULTS: Two hundred and fifty nine out of 820 (31.6%) of subjects aged ≥ 5 years had W. bancrofti antigenaemia and 11.8% (97/820) had microfilaraemia. Multivariable analysis of risk factors for antigenaemia demonstrated increased risk for males (aOR = 1.75, 95% CI: 1.20-2.53, P = 0.003), for older individuals (aOR = 9.12 in those aged > 35 years, 95% CI: 4.47-18.61, P < 0.001), for people not using bednets (aOR = 1.57, 95% CI: 1.06-2.33, P = 0.023), for farmers (aOR = 2.21, 95% CI: 1.25-3.90, P = 0.006), and for those who live close to a river (aOR = 2.78, 95% CI: 1.14-6.74, P = 0.024). Significant risk factors for microfilaraemia included age, male gender, overnight stay in the bush, and residence close to a river (aOR = 1.86, 2.01, 2.73; P = 0.011, 0.010, 0.041; for the three latter variables, respectively). People who reported having taken levamisole (n = 117) during the prior year had a significantly decreased risk of having filarial antigenaemia (aOR = 0.40, 95% CI: 0.21-0.76, P = 0.005). CONCLUSIONS: Age, sex, not using bednets, and occupation-dependent exposure to mosquitoes were important risk factors for infection with W. bancrofti in this study. The association with levamisole use suggests that the drug may have prevented filarial infections. Other results suggest that transmission often occurs outside of the village. This study provides interesting clues regarding the epidemiology of LF in Central Africa.