Abstract
We followed up the 1996 baseline parasitological and entomological studies on onchocerciasis transmission in eleven health districts in West Region, Cameroon. Annual mass ivermectin treatment had been provided for 15 years. Follow-up assessments which took place in 2005, 2006, and 2011 consisted of skin snips for microfilariae (mf) and palpation examinations for nodules. Follow-up Simulium vector dissections for larval infection rates were done from 2011 to 2012. mf prevalence in adults dropped from 68.7% to 11.4%, and nodule prevalence dropped from 65.9% to 12.1%. The decrease of mf prevalence in children from 29.2% to 8.9% was evidence that transmission was still continuing. mf rates in the follow-up assessments among adults and in children levelled out after a sharp reduction from baseline levels. Only three health districts out of 11 were close to interruption of transmission. Evidence of continuing transmission was also observed in two out of three fly collection sites that had infective rates of 0.19% and 0.18% and ATP of 70 (Foumbot) and 300 (Massangam), respectively. Therefore, halting of annual mass treatment with ivermectin cannot be done after 15 years as it might escalate the risk of transmission recrudescence.
Highlights
Onchocerciasis, a leading cause of blindness, is due to human infection with Onchocerca volvulus, a parasitic worm that forms nodules under the skin
Results of this study revealed that, while the onchocerciasis foci in the health districts of Tchollire and Rey Bouba appeared to fulfill the Diawara criteria of elimination, in the Health District of Touboro, transmission was still going on
The objective of the present study was to determine whether 15 years of annual treatment with ivermectin in West Region, a different ecological setting, had interrupted the transmission of onchocerciasis as had been observed in Mali and Senegal [11]
Summary
Onchocerciasis, a leading cause of blindness, is due to human infection with Onchocerca volvulus, a parasitic worm that forms nodules under the skin. The female worms produce microfilariae (mf) that live in the nodules, inflame the skin, and enter the eyes, giving rise to inflammatory lesions. Ivermectin is a safe and effective microfilaricidal drug that has been donated by Merck & Co (Mectizan) since 1987 for mass treatment of onchocerciasis. This medicine kills the microfilaria and reduces the risk of developing eye Journal of Parasitology Research and skin diseases associated with the infection. Ivermectin reduces the fecundity of adult worms and apparently shortens their life span [1]. Treatment may be given for undetermined period of time in order to effect cure [2, 3]
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