Optimization of Slash and Clear Community-Directed Control of Simulium damnosum Sensu Stricto in Northern Uganda

Benjamin Jacob College of Public Health, University of South Florida, Tampa, Florida;

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Denis Loum Nwoya District Local Government, Nwoya, Uganda;

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Denis Munu The Carter Center, Uganda Office, Kampala, Uganda;

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Thomson Lakwo Vector Control Division, Ministry of Health, Kampala, Uganda;

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Edson Byamukama The Carter Center, Uganda Office, Kampala, Uganda;

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Peace Habomugisha The Carter Center, Uganda Office, Kampala, Uganda;

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Eddie W. Cupp Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida

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Thomas R. Unnasch Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida

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ABSTRACT

Onchocerciasis, caused by infection with Onchocerca volvulus, has been targeted for elimination by 2030. Currently, onchocerciasis elimination programs rely primarily on mass distribution of ivermectin. However, ivermectin alone may not be sufficient to achieve elimination in some circumstances, and additional tools may be needed. Vector control has been used as a tool to control onchocerciasis, but vector control using insecticides is expensive and ecologically detrimental. Community-directed removal of the trailing vegetation black fly larval attachment sites (slash and clear) has been shown to dramatically reduce vector biting densities. Here, we report studies to optimize the slash and clear process. Conducting slash and clear interventions at Simulium damnosum sensu stricto breeding sites located within 2 km of afflicted communities resulted in a 95% reduction in vector biting. Extending slash and clear further than 2 km resulted in no further decrease. A single intervention conducted at the first half of the rainy season resulted in a 97% reduction in biting rate, whereas an intervention conducted at the end of the rainy season resulted in a 94% reduction. Vector numbers in any of the intervention villages did not fully recover by the start of the following rainy season. These results suggest that slash and clear may offer an inexpensive and effective way to augment ivermectin distribution in the effort to eliminate onchocerciasis in Africa.

Author Notes

Address correspondence to Thomas R. Unnasch, Global Health Infectious Disease Program, 3720 Spectrum Blvd., Suite 304 Tampa, FL 33612. E-mail: tunnasch@usf.edu

Financial support: This study was supported by a grant from the U.S. National Institute of Allergy and Infectious Diseases to T. L. and T. R. U. (Award #1 R01 AI123245-01).

Authors’ addresses: Benjamin Jacob, College of Public Health, Global and Planetary Health, Tampa, FL, E-mail: bjacob1@usf.edu. Denis Loum, Health Department, Nwoya District Local Government, Gulu, Uganda, E-mail: loumdenis2@gmail.com. Denis Munu, Edson Byamukama, and Peace Habomugisha, The Carter Center Uganda, Kampala, Uganda, E-mails: denis.munu@gmail.com, edson.navs@gmail.com, and peace.habo@cartercenter.org. Thomson Lakwo, Vector Control Division, Ministry of Health, Kampala, Uganda, E-mail: tlakwo@gmail.com. Eddie W. Cupp, Center for Global Health Infectious Disease Research, Tampa, FL, E-mail: cuppedd@auburn.edu. Thomas R. Unnasch, Global Health Infectious Disease Program, Tampa, FL, E-mail: tunnasch@usf.edu.

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