Elimination of human onchocerciasis: progress report, 2020

Overview

Onchocerciasis or river blindness is a parasitic disease caused by the filarial nematode Onchocerca volvulus. Onchocerciasis is called river blindness because the blackflies, of the genus Simulium, that transmit the infection, live and breed along rivers and streams in areas where there is fast-moving water and because infection with the parasite can result in vision loss and blindness. Onchocerciasis is set for elimination globally. Currently, more than 240 million people live in areas known to be endemic for onchocerciasis. However, the risk of onchocerciasis-related blindness or skin disease is reduced thanks to the continued mass drug administration (MDA) with ivermectin. Four countries (Colombia, Ecuador, Guatemala and Mexico) have completed the WHO recommended process for verification of the interruption of transmission of human onchocerciasis, and many others have stopped MDA, completed post-treatment surveillance (PTS) or both in at least one transmission area in their territory. Interruption of transmission allows countries to protect the gains made during many years of effective MDA with ivermectin and to stop MDA permanently, preventing the populations living in endemic areas from the risk of morbidity and infection. Elimination of human onchocerciasis would make a significant contribution to the attainment of Sustainable Development Goal (SDG) 3.3, which includes a call to end the epidemic of neglected tropical diseases (NTDs) by 2030.

All onchocerciasis-endemic countries have reported cases of COVID-19. The effect of the pandemic on NTD interventions has been summarized elsewhere. Efforts to mitigate the spread of SARS-CoV-2 in onchocerciasis endemic countries delayed planned MDA rounds in many countries. Compared to 2019, the number of people treated for onchocerciasis declined by 26.9%. MDA was implemented in fewer countries and implementation units (1096 in 2020 comparing to 1538 in 2019) resulting in a drop of 27.7% in global geographical coverage. Data reported by the countries is available in the WHO Global Health Observatory.