Abstract
.Plateau and Nasarawa states in central Nigeria were endemic for onchocerciasis. The rural populations of these two states received annual ivermectin mass drug administration (MDA) for a period of 8–26 years (1992–2017). Ivermectin combined with albendazole was given for 8–13 of these years for lymphatic filariasis (LF); the LF MDA program successfully concluded in 2012, but ivermectin MDA continued in areas known to have a baseline meso-/hyperendemic onchocerciasis. In 2017, serological and entomological assessments were undertaken to determine if MDA for onchocerciasis could be stopped in accordance with the current WHO guidelines. Surveys were conducted in 39 sites that included testing 5- to < 10-year-old resident children by using ELISA for OV16 IgG4 antibodies, and Onchocerca volvulus O150 pooled polymerase chain reaction (PCR) testing of Simulium damnosum s.l. vector heads. Only two of 6,262 children were OV16 positive, and none of 19,056 vector heads were positive for parasite DNA. Therefore, both states were able to meet WHO stop-MDA thresholds of an infection rate in children of < 0.1% and a rate of infective blackflies of <1/2,000, with 95% statistical confidence. Transmission of onchocerciasis was declared interrupted in Plateau and Nasarawa states by the Federal Ministry of Health, and 2.2 million ivermectin treatments/year were stopped in 2018. Post-treatment Surveillance was launched focusing on entomological monitoring on borders with neighboring onchocerciasis-endemic states. An apparent positive impact of the LF MDA program on eliminating hypo-endemic onchocerciasis was observed. This is the first stop-MDA decision for onchocerciasis in Nigeria and the largest single stop-MDA decision for onchocerciasis yet reported. This achievement, along with the process used in adapting and implementing the 2016 WHO stop-MDA guidelines, will be important as a potential model for decision makers and national onchocerciasis elimination committees in other African countries that are charged with advancing their programs.
Highlights
Human onchocerciasis (“river blindness”) is a parasitic infection caused by the filarial nematode Onchocerca volvulus.[1]
Ivermectin combined with albendazole was given for 8–13 of these years for lymphatic filariasis (LF); the LF mass drug administration (MDA) program successfully concluded in 2012, but ivermectin MDA continued in areas known to have a baseline meso-/hyperendemic onchocerciasis
Surveys were conducted in 39 sites that included testing 5- to < 10-year-old resident children by using ELISA for OV16 IgG4 antibodies, and Onchocerca volvulus O150 pooled polymerase chain reaction (PCR) testing of Simulium damnosum s.l. vector heads
Summary
Human onchocerciasis (“river blindness”) is a parasitic infection caused by the filarial nematode Onchocerca volvulus.[1]. The parasite is transmitted by certain species of Simulium blackflies, with the most common vector being Simulium damnosum sensu lato (s.l.).[2] In humans, the adult worms cluster in subcutaneous fibrous onchocercomas (commonly referred to as “nodules”) that are often visible and/or palpable. In these nodules, fertilized females release microfilariae (mf) that migrate in the sub dermis and eye, causing immune reactions that result in the major morbidities associated with the infection. The mf eventually develop into the third-stage larvae (L3) that are infectious to humans on subsequent blood meals. There are no known environmental or epidemiologically important animal reservoirs of O. volvulus.[3]
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