The impact of ivermectin mass drug administration on the level of endemicity and intensity of Onchocerca Volvulus infection in the Adansi South District of Ghana
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Date
2014-08-26
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Abstract
Onchocerca volvulus infection remains a major public health problem with more than 120 million people estimated to be living in endemic areas, majority in sub-Saharan Africa. Clinical manifestations include severe dermatitis, visual impairment, and blindness. Ivermectin has been the main operational drug for the treatment and control of onchocerciasis. However reports have emerged about sub-optimal response to this drug in Ghana posing a challenge to the control of O. volvulus infection. In this study, the impact of ivermectin mass drug administration on the level of endemicity and intensity of O. volvulus infection was assessed. About 1223 volunteers from 19 hyperendemic communities in two sub-district areas, who had received 3 to 5 rounds of ivermectin were examined by palpation for onchocercal nodules. Out of the 1223 volunteers, 444 were assessed for microfilaria loads and the community microfilarial load (CMFL) for each of the study communities was determined. Level of endemicity was measured using onchocercal nodule and microfilarial prevalence while the intensity of infection was measured by CMFL, a reference index used by the OCP. At the end of the study, 41.8% of the 1223 volunteers were nodule positive. A significant difference was observed (p=0.0107) in the nodule prevalence between New Edubiase and Akrofuom sub-districts. Of the 444 volunteers, 54.5% were microfilaria positive. The microfilaria prevalence and community microfilarial load in the study communities ranged from 13.3% to 88.9% and 1.4mf/mg to 5.2mf/mg respectively. There was no significant difference in the microfilarial prevalence (p=1.000) and CMFL (p=0.3539) between the two study areas. The overall nodule and microfilarial prevalence in the study areas suggest that these areas are mesoendemic for O. volvulus infection and the intensity of infection as suggested by an average CMFL of 2.7mf/mg is below APOC’s threshold of 5mf/s. This study has shown that 3 to 5 rounds of ivermectin treatment has significant impact on the level of endemicity and intensity of O. volvulus infection which means ivermectin still remains an effective tool for the control of onchocerciasis.
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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, 2014