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Transmission of Onchocerca volvulus Continues in Nyagak-Bondo Focus of Northwestern Uganda after 18 Years of a Single Dose of Annual Treatment with Ivermectin

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  • The Carter Center, Atlanta, Georgia; Vector Control Division, Ministry of Health, Kampala, Uganda; The Carter Center, Kampala, Uganda; Health Services, Kabarole District, FortPortal, Uganda; Health Services, Nebbi District, Nebbi, Uganda; Health Services, Zombo District, Zombo, Uganda; ENVISION, ENVISION/RTI International, Kampala, Uganda; National Disease Control, Ministry of Health, Kampala, Uganda; Entomology, Lythan St. Anne's, Lancashire, United Kingdom; Global Health, University of South Florida, Tampa, Florida

The objective of the study was to determine whether annual ivermectin treatment in the Nyagak-Bondo onchocerciasis focus could safely be withdrawn. Baseline skin snip microfilariae (mf) and nodule prevalence data from six communities were compared with data collected in the 2011 follow-up in seven communities. Follow-up mf data in 607 adults and 145 children were compared with baseline (300 adults and 58 children). Flies collected in 2011were dissected, and poolscreen analysis was applied to ascertain transmission. Nodule prevalence in adults dropped from 81.7% to 11.0% (P < 0.0001), and mf prevalence dropped from 97.0% to 23.2% (P < 0.0001). In children, mf prevalence decreased from 79.3% to 14.1% (P < 0.0001). Parous and infection rates of 401 flies that were dissected were 52.9% and 1.5%, respectively, whereas the infective rate on flies examination by polymerase chain reaction (PCR) was 1.92% and annual transmission potential was 26.9. Stopping ivermectin treatment may result in onchocerciasis recrudescence.

Author Notes

* Address correspondence to Moses N. Katabarwa, The Carter Center, One Copenhill, 453 Freedom Parkway Atlanta, GA 30307. E-mail: mkataba@emory.edu

Authors' addresses: Moses N. Katabarwa, The Carter Center, Atlanta, GA, E-mail: mkataba@emory.edu. Tom Lakwo, David Oguttu, and Edridah M. Tukahebwa, Vector Control Division, Ministry of Health, Kampala, Uganda, E-mails: tlakwo@gmail.com, dguttu@gmail.com, and edmuheki@gmail.com. Peace Habomugisha, Stella Agunyo, and Edson Byamukama, Health Programs, The Carter Center, Kampala, Uganda, E-mails: provia5@hotmail.com, agunyoegunyu@gmail.com, and edson.navs@gmail.com. Ephraim Tukesiga, Health Services, Kabarole District, FortPortal, Uganda, E-mail: ephraim.tukesiga@gmail.com. Dickson Unoba, Health Services, Nebbi District, Nebbi, Uganda, E-mail: unoba2@gmail.com. Patrick Dramuke, Health Services, Zombo District, Zombo, Uganda, E-mail: dramuke.patrick@gmail.com. Ambrose Onapa, ENVISION, RTI International, Kampala, Uganda, E-mail: kwibale1@yahoo.co.uk. Dennis Lwamafa, National Disease Control, Ministry of Health, Kampala, Uganda, E-mail: lwamafa@yahoo.co.uk. Frank Walsh, Entomology, Lythan St. Anne's, Lancashire, UK, E-mail: frank@walsh.me.uk. Thomas R. Unnasch, Global Health, University of South Florida, Tampa, FL, E-mail: tunnasch@health.usf.edu.

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