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The Imaramagambo Onchocerciasis Focus in Southwestern Uganda: Interruption of Transmission After Disappearance of the Vector Simulium neavei and Its Associated Freshwater Crabs

Friday, 5th of August 2016

1. 1.   Am J Trop Med Hyg 2016 vol. 95 no. 2 417-425

 

The Imaramagambo Onchocerciasis Focus in Southwestern Uganda: Interruption of Transmission After Disappearance of the Vector Simulium neavei and Its Associated Freshwater Crabs

1. 1.   Moses N. Katabarwa1,*,
2. 2.   James Katamanywa2,
3. 3.   Thomson Lakwo3,
4. 4.   Peace Habomugisha4,
5. 5.   Edson Byamukama4,
6. 6.   David Oguttu3,
7. 7.   Christine Nahabwe3,
8. 8.   Monica Ngabirano3,
9. 9.   Ephraim Tukesiga2,

10. Annet Khainza4,

11. Edridah Tukahebwa3,

12. Thomas R. Unnasch5,

13. Frank O. Richards1 and

14. Rolf Garms6

- Author Affiliations

1.    ¹Health Programs, The Carter Center, Atlanta, Georgia.

2.    ²Health Services, Kabarole District, Fort Portal, Uganda.

3.    ³Vector Control Division, Ministry of Health, Kampala, Uganda.

4.    ⁴Health Programs, The Carter Center, Kampala, Uganda.

5.    ⁵University of South Florida, Global Health, Tampa, Florida.

6.    ⁶Tropical Medicine Department, Bernhard Nocht Institute of Tropical Medicine, Hamburg, Germany.

- Author Notes

       Authors addresses: Moses N. Katabarwa and Frank O. Richards, Health Programs, The Carter Center, Atlanta, GA, E-mails: moses.katabarwa@cartercenter.org and frank.richards@cartercenter.org. James Katamanywa and Ephraim Tukesiga, Health Services, Kabarole District, Fort Portal, Uganda, E-mails: jkatamanywawilly@gmail.com and ephraim.tukesiga@gmail.com. Thomson Lakwo, David Oguttu, Christine Nahabwe, Monica Ngabirano, and Edridah Tukahebwa, Vector Control Division, Ministry of Health, Kampala, Uganda, E-mails: tlakwo@gmail.com, dguttu@gmail.com, ch.nahabwe@gmail.com, ngabiranomonica@ymail.com, and edmuheki@gmail.com. Peace Habomugisha, Edson Byamukama, and Annet Khainza, Health Programs, The Carter Center, Kampala, Uganda, E-mails: peace.habo@cartercenter.org, edson.byamukama@cartercenter.org, and annet.khainza@cartercenter.org. Thomas R. Unnasch, University of South Florida, Global Health, Tampa, FL, E-mail: tunnasch@health.usf.edu. Rolf Garms, Department of Tropical Medicine, Bernhard Nocht Institute of Tropical Medicine, Hamburg, Germany, E-mail: garms@bni-hamburg.de.

1. ↵* Address correspondence to Moses N. Katabarwa, Health Programs, The Carter Center, One Copenhill, 453 Freedom Parkway, Atlanta, GA 30307. E-mail: moses.katabarwa@cartercenter.org

Abstract below; full text is at http://www.ajtmh.org/content/95/2/417.full.pdf+html

 

It was not until early 1990s that, when the Imaramagambo focus of southwest Uganda was mapped, mass treatment with a single annual dose of ivermectin for onchocerciaisis control commenced. However, comprehensive investigations on its transmission were launched after a nationwide policy for onchocerciasis elimination in 2007. Entomological surveys throughout the focus from 2007 to 2015 have yielded few or no freshwater crabs (Potamonautes aloysiisabaudiae), which serve as the obligate phoretic host of the larvae and pupae of the vector Simulium neavei. No S. neavei flies have been observed or collected since 2007. Skin snips (microscopy) from 294 individuals in 2008 were negative for skin microfilariae, and of the 462 persons analyzed by polymerase chain reaction skin snip poolscreen in 2009, only five (1.08%) persons were indicated as infected with onchocerciasis. All five of the positive persons were at least 40 years old. Serosurvey results showed negative exposure among 3,332 children in 2012 and 3,108 children in 2015. Both were within the upper bound of the 95% confidence interval of the prevalence estimate of 0.06%, which confirmed the elimination of onchocerciasis. Treatment coverage in Imaramagambo was generally poor, and transmission interruption of onchocerciasis could not be attributed solely to annual mass treatment with ivermectin. There was sufficient evidence to believe that the possible disappearance of the S. neavei flies, presumed to have been the main vector, may have hastened the demise of onchocerciasis in this focus.

       Received March 7, 2016.

       Accepted April 4, 2016.

       © The American Society of Tropical Medicine and Hygiene

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