Effect of doxycycline treatment on Onchocerca volvulus worms that respond poorly to Ivermectin
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Date
2011-06-19
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Abstract
Onchocerciasis is a significant public health concern especially in sub-Saharan African countries. Despite more than 20 years of ivermectin mass treatment programmes in endemic areas in the Pru and Lower Black Volta river basins, cases of recrudescence of infections in individuals suggestive of sub-optimal responses of Onchocerca volvulus to ivermectin have been reported. In this study, the effect of doxycycline (a licensed tetracycline) therapy on onchocerciasis patients responding sub-optimally to previous multiple treatments with ivermectin was assessed. A total of 149 onchocerciasis-infected volunteers were treated with either 100 mg/day doxycycline (n = 73) or matching placebo (n = 76) for 6 weeks. All study volunteers were allowed to take 2 rounds of 150 mg/kg ivermectin during the study period. Microfilaridermia levels of all study volunteers were monitored at pre-treatment, 12 months and 20 months post-treatment using skin biopsies. At the end of the study, there was a highly significant difference (p < 0.0001) in the number of microfilaridermic volunteers between the doxycycline and placebo groups, with the doxycycline group showing a drastic reduction from 65.7% to 2.9% whiles the placebo group showed a marginal increase from 63.2% to 69.0%. There was also a highly significant difference (p < 0.0001) in the microfilarial geometric mean load of volunteers between the two groups, with the doxycycline group showing a drastic reduction from 1.3 to 0.2 whiles the placebo group showed a marginal increase from 1.3 to 1.7 despite 2 treatment rounds of ivermectin during the study period. Doxycycline therefore proved to be effective in this study and is thus recommended as a front-line therapy for use in clearing microfilariae from individuals who seem to be responding sub-optimally to repeated ivermectin therapy.
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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.