Abstract
ABSTRACT.The lack of a WHO-recommended strategy for onchocerciasis treatment with ivermectin in hypo-endemic areas co-endemic with loiasis is an impediment to global onchocerciasis elimination. New loiasis diagnostics (LoaScope; Loa antibody rapid test) and risk prediction tools may enable safe mass treatment decisions in co-endemic areas. In 2017–2018, an integrated mapping strategy for onchocerciasis, lymphatic filariasis (LF), and loiasis, aimed at enabling safe ivermectin treatment decisions, was piloted in Gabon. Three ivermectin-naïve departments suspected to be hypo-endemic were selected and up to 100 adults per village across 30 villages in each of the three departments underwent testing for indicators of onchocerciasis, LF, and loiasis. An additional 67 communities in five adjoining departments were tested for loiasis to extend the prevalence and intensity predictions and possibly expand the boundaries of areas deemed safe for ivermectin treatment. Integrated testing in the three departments revealed within-department heterogeneity for all the three diseases, highlighting the value of a mapping approach that relies on cluster-based sampling rather than sentinel sites. These results suggest that safe mass treatment of onchocerciasis may be possible at the subdepartment level, even in departments where loiasis is present. Beyond valuable epidemiologic data, the study generated insight into the performance of various diagnostics and the feasibility of an integrated mapping approach utilizing new diagnostic and modeling tools. Further research should explore how programs can combine these diagnostic and risk prediction tools into a feasible programmatic strategy to enable safe treatment decisions where loiasis and onchocerciasis are co-endemic.
Highlights
There is no WHO-recommended strategy to eliminate onchocerciasis in countries endemic for Loa loa because of the concern about serious adverse events (SAEs) that may occur when ivermectin (IVM) is given as part of mass drug administration (MDA) to individuals with highintensity (. 20,000 mf/mL) L. loa infections.[1,2] This represents a substantial obstacle in the global effort to eliminate onchocerciasis.[3]
In BoumiLouetsi, one of the three departments selected for the joint mapping of lymphatic filariasis (LF), onchocerciasis, and loiasis, only 26 of the 30 selected villages were visited due to challenges with accessibility
Fifty-four percent of respondents were women, the proportion of females in the sample varied by department, ranging from 48.5% in Mongo to 60% in Boumi-Louetsi (Table 1)
Summary
There is no WHO-recommended strategy to eliminate onchocerciasis in countries endemic for Loa loa because of the concern about serious adverse events (SAEs) that may occur when ivermectin (IVM) is given as part of mass drug administration (MDA) to individuals with highintensity (. 20,000 mf/mL) L. loa infections.[1,2] This represents a substantial obstacle in the global effort to eliminate onchocerciasis.[3]. 20,000 mf/mL) L. loa infections.[1,2] This represents a substantial obstacle in the global effort to eliminate onchocerciasis.[3] In L. loa co-endemic areas where onchocerciasis is classified as “meso- “or “hyper-endemic” (nodule rate $ 20% and/or microfilaria prevalence $ 40%), IVM treatment was recommended despite the heightened risk of SAEs, due to the benefit of treatment in preventing blindness.[4] Strategies for areas where onchocerciasis is “hypoendemic” (nodule rate , 20% and/or microfilaria prevalence , 40%) and the risk of blindness is much less, require more care in making treatment decisions, given that the prevalence of loiasis (and high-intensity infections, in particular) may vary widely within countries or even within health districts. The test is useful given that it can be performed at any time of day, unlike the restrictions for using the ELLA AND OTHERS
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