Evaluation of epidemiological mapping strategies and diagnostic tool for onchocerciasis and lymphatic filariasis in hypo-endemic Amaya district, South-Western Ethiopia

Abstract

Abstract Onchocerciasis is a parasitic neglected tropical disease caused by a filarial nematode called Onchocerca volvulus. During the period of the onchocerciasis control program in Ethiopia, larger areas with onchocerciasis prevalence of less than 20% were classified as hypo-endemic. In 2012, the goal of the program has been shifted from control to elimination, which required the evaluation of mapping strategies and assessment of transmission status. However, there is no clear mapping strategy for onchocerciasis and lymphatic filariasis in the elimination context in these areas. Hence, the study evaluated the mapping strategies in first-line and randomly selected villages and matched school children to random villages. Methods A cross-sectional study involving a total of 2756 study participants; 1181 from four purposively selected first-line villages, 372 from random villages, and 1203 from matched schools children to random villages was conducted in 2019 at Amaya district South-western Shoa zone of Oromia region of Ethiopia. Approximately 175 µL finger prick blood was collected from each study participant. Oncho/LF IgG4 bi-plex rapid diagnostic test was conducted using 10 µL blood and dried blood spot were prepared using the remaining blood samples for further conformation by SD-ELISA. Data were captured using open data kit software programmed tablet, exported, and analyzed by SPSS version 23 software. The sensitivity and specificity of the Oncho/LF IgG4 bi-plex test were evaluated against SD-ELISA as the reference standard based on the manufacturer’s claims. Results The prevalence of onchocerciasis among first-line, randomly selected villages and matched-school children in random villages were 8.3%, 4.6%, and 0.33% respectively. The prevalence of lymphatic filariasis in first-line villages was 1.02%, while 1.1% in random villages. The co-endemicity of onchocerciasis with lymphatic filariasis was 0.42% in the first line and 1.08% in randomly selected villages. The sensitivity and specificity of the Oncho/LF IgG4 bi-plex test were 26.09 % and 99.93%. Conclusions The study indicated Amaya district qualifies for onchocerciasis mass drug administration threshold (>2%) average in both first-line and randomly selected villages. In both first and random villages, onchocerciasis and lymphatic filariasis were co-endemic indicating the need of integrating mapping strategies. First-line and random village-based mapping strategies are recommended for onchocerciasis in hypo-endemic areas.