One Hundred Years After Its Discovery in Guatemala by Rodolfo Robles, Onchocerca volvulus Transmission Has Been Eliminated from the Central Endemic Zone

Abstract

Abstract. We report the elimination of Onchocerca volvulus transmission from the Central Endemic Zone (CEZ) of onchocerciasis in Guatemala, the largest focus of this disease in the Americas and the first to be discovered in this hemisphere by Rodolfo Robles Valverde in 1915. Mass drug administration (MDA) with ivermectin was launched in 1988, with semiannual MDA coverage reaching at least 85% of the eligible population in > 95% of treatment rounds during the 12-year period, 2000-2011. Serial parasitological testing to monitor MDA impact in sentinel villages showed a decrease in microfilaria skin prevalence from 70% to 0%, and polymerase chain reaction (PCR)-based entomological assessments of the principal vector Simulium ochraceum s.l. showed transmission interruption by 2007. These assessments, together with a 2010 serological survey in children 9-69 months of age that showed Ov16 IgG4 antibody prevalence to be < 0.1%, meeting World Health Organization (WHO) guidelines for stopping MDA, and treatment was halted after 2011. After 3 years an entomological assessment showed no evidence of vector infection or recrudescence of transmission. In 2015, 100 years after the discovery of its presence, the Ministry of Health of Guatemala declared onchocerciasis transmission as having been eliminated from the CEZ. INTRODUCTION Human onchocerciasis (river blindness) is caused byOnchocerca volvulus, a tissue-dwelling filarial nematode transmitted by certain species of the genus Simulium.1 Adult male and female worms form fibrous, often palpable, subcutaneous onchocercomas ("nodules"), in which fertilized female worms produce microfilariae (mf). The mf leave the nodule and reside in the dermis. They may also enter the eyes. Human disease results largely from death of the mf, which results in inflammation, itching, visual impairment, and blindness. The Simulium ("black fly") vectors breed in rapidly flowing rivers and streams and become infected when they ingest mf during a blood meal; in competent black fly species, mf develop into third stage larvae that can infect humans when the vector takes a subsequent blood meal. There are no important animal reservoirs of O. volvulus to maintain the transmission cycle independent of the human population itself. Human onchocerciasis is thought to have originated in Africa when Onchocerca species in ungulates adapted to man; the parasite is believed to have been brought to the Americas through the Atlantic slave trade.3 Transmission was only focally established in the Americas, in contrast to the extensive transmission zones that exist in Africa. In the Americas, due to a limited distribution of competent vectors, transmission zones ("foci") are small and sharply delimited geographically, and are generally maintained by high vector biting rates. Before control measures were implemented, there were 13 foci in six countries in Latin America (Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela), with an overall human population at risk in 2013 of just over 500,000 persons. 4Guatemala...

Elimination of onchocerciasis from Colombia: first proof of concept of river blindness elimination in the world

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Post-elimination surveillance in formerly onchocerciasis endemic focus in Southern Mexico

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Operational Performance of the Onchocerca volvulus “OEPA” Ov16 ELISA Serological Assay in Mapping, Guiding Decisions to Stop Mass Drug Administration, and Posttreatment Surveillance Surveys

“…The OEPA Ov16 ELISA, coupled with polymerase chain reaction (PCR) confirmation of skin biopsies (snips) to detect patent infections in Ov16-positive individuals, has been used for a decade as a tool in successful stop-MDA surveys in Latin America and Africa. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] To evaluate the specificity of the OEPA Ov16 ELISA, we collected and analyzed the raw data from all successful stop-MDA surveys conducted by Carter Centerassisted laboratories in Latin America and Africa where individuals positive in the Ov16 ELISA were subject to confirmation using skin snip PCR, following WHO recommendations. Data from one PTS study from Sudan, which included a serological component, was also included.…”