What does the COVID-19 pandemic mean for the next decade of onchocerciasis control and elimination?

Hamley, Jonathan I. D.; Blok, David J.; Walker, Martin; Milton, Philip; Hopkins, Adrian D.; Hamill, Louise C.; Downs, Philip; Vlas, Sake J. de; Stolk, Wilma A.; Basanez, Maria-Gloria

BackgroundMass drug administration (MDA) of ivermectin for onchocerciasis has been disrupted by the SARS-CoV-2 (COVID-19) pandemic. Mathematical modelling can help predict how missed/delayed MDA will affect short-term epidemiological trends and elimination prospects by 2030. MethodsTwo onchocerciasis transmission models (EPIONCHO-IBM and ONCHOSIM) are used to simulate microfilarial prevalence trends, elimination probabilities, and age-profiles of Onchocerca volvulus microfilarial prevalence and intensity, for different treatment histories and transmission settings, assuming no interruption, a 1-year (2020) or 2-year (2020-2021) interruption. Biannual MDA or increased coverage upon MDA resumption are investigated as remedial strategies. ResultsProgrammes with shorter MDA histories and settings with high pre-intervention endemicity will be the most affected. Biannual MDA is more effective than increasing coverage for mitigating COVID-19s impact on MDA. Programmes which had already switched to biannual MDA should be minimally affected. In high transmission settings with short treatment history, a 2-year interruption could lead to increased microfilarial load in children (EPIONCHO-IBM) or adults (ONCHOSIM). ConclusionsProgrammes with shorter (annual MDA) treatment histories should be prioritised for remedial biannual MDA. Increases in microfilarial load could have short- and long-term morbidity and mortality repercussions. These results can guide decision-making to mitigate the impact of COVID-19 on onchocerciasis elimination.