District Mapping Onchocerciasis, Lymphatic Filariasis, and Loiasis in Cameroon

The goals of the study were to pilot a strategy for mapping and treating onchocerciasis and lymphatic flilariasis (LF) in Loa loa co-endemic areas; to validate the use of the LoaScope in community assessments; and to validate a statistical model calibrated to determine whether community-level prevalence of Loa infection of >20,000 mf/mL is less than 1% in a community by comparing results of the model to results of a community-level random sample prevalence assessment. A community-based cross sectional cluster survey was organized in the Garoua Boulai health district (East Region, Cameroon) where no ivermectin mass administration was ever performed. The prevalence of loiasis was 8.0% (95% CI: 7.2 – 9.0) and was quite different from one cluster to another (Minimum: 0.0%; Maximum: 43.5%). Onchocerciasis was found to be hypo-endemic (rate of exposure: 4.9%; 95% CI: 4.2 – 5.7), and the endemicity of LF was quite low (prevalence: 0.4%; 95% CI: 0.2 – 0.7). The likelihood of finding more than 1% of individuals harboring Loa mf densities higher than 20,000 mf/mL in a cluster was positively associated with the prevalence of loiasis, although a clear prevalence cut off is yet to be computed.