The impact of ten years of ivermectin mass drug administration on the level of endemicity and intensity of Onchocerca Volvulus infection in the Aowin District of Ghana

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Ivermectin remains the only safe drug for the control and treatment of onchocercisis in endemic areas. Despite some reports on its sub-optimal response in some parts of Ghana, long term treatment has shown that it can eliminate the infection and interrupt transmission in Africa. Taking into account the feasibility of elimination of onchocerciasis infection and transmission interruption with ivermectin mass treatment alone, Joint Action Forum (JAF), and the governing body of African Programme for Onchocerciasis Control in 2011, has reaffirmed its endorsement for the Programme to pursue the elimination of onchocerciasis in Africa. Aowin district of the Western Region of Ghana is meso-endemic for onchocerciasis infection and had received ivermectin mass drug treatment for 10 years. This study was undertaken to assess the impact of 10 years of mass drug administration with ivermectin on the level of endemicity and intensity of O. volvulus infection in Aowin district following the claim made by the District Health Directorate that onchocerciasis transmission and infection had been eliminated in the district. A cross sectional survey was conducted in 20 endemic communities situated along rivers in the district. In all, 1,698 volunteers took part in the study. They were examined by palpation for onchocercal nodules or onchodermatitis. Of the 1,698 volunteers examined, 300 who were positive for palpable nodules or onchodermatitis were skin-snipped for microfilarial load assessment. Community microfilarial load (CMFL) for each of the studied community was also determined. Onchocercal nodules and microfilarial prevalence were used to measure the level of endemicity. The intensity of infection was measured using CMFL, a reference index used by the Onchocerciasis Control Programme. The results indicated that, 298 (17.6%) out of the 1,698 examined had palpable nodules. A significant difference was observed (p=0.0001) in the nodule prevalence between males and females. Out of the 300 skin snipped, 173 (57.7%) were microfilarial-positive. The microfilarial prevalence and community microfilarial load in the study communities ranged from 8.3-88.9% and 1.0-5.2mf/mg respectively. The overall nodule and microfilarial prevalence recorded suggest strong evidence of on-going transmission of onchocerciasis despite 10 years of annual mass treatment. Halting ivermectin treatment in the district is not recommended as it might risk recrudescence of transmission.  
A thesis submitted to the Department of Clinical Microbiology, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Philosophy (Clinical Microbiology) School of Medical Sciences, College of Health Sciences 2016.