The impact of Ivermectin mass treatment on the prevalence of onchocerciasis by rapid epidemiological assessment in Galadimawa, Kaduna state, Nigeria

Abstract

The impact of repeated mass treatment with ivermectin on the prevalence of onchocerciasis in Galadimawa, Kaduna State, Nigeria, was assessed. The 1988 pre-ivermectin treatment baseline data was compared with the 12 years post-ivermectin mass treatment prevalence of clinical manifestations of the disease (1989-2001) obtained in January 2002. The Rapid Epidemiological Assessment (REA) method was used to determine the prevalence of palpable nodules as an alternative to the more invasive skin snipping. From the 1988 pre-control data, 717 persons were examined of which 176 (24.5 %) had nodules. Parasitological confirmation by skin snipping of the same individuals revealed 346 (48.3 %) persons with Onchocerca volvulus microfilaria. In 2002, 700 persons were examined by REA alone, of which 53 (7.6 %) had nodules. Prevalence reduction post-ivermectin mass treatment was significant for palpable nodules (p<0.001) and blindness (p=0.0014). Females had insignificant higher prevalences in all the clinical manifestations than males, except for hanging groin which was absent in the females both in1988 and 2002. Nodule prevalence correlated positively and significantly with age (r=0.91, p=0.005) and was significantly associated with adult females (p<0.01), contrary to reported findings in other communities where nodule prevalence was associated with adult males.

Key words: Impact assessment, ivermectin, onchocerciasis, nodules, prevalence.