Onchocerciasis in Imo state, Nigeria (2): the prevalence, intensity and distribution in the upper Imo river basin

Human infection with Onchocerca volvulus was investigated in 13 rural communities in the Upper Imo River basin, Imo State, Nigeria between March 1997 and December 2000 using the skin snip method. Of the 3,311 persons examined, 889 (26.8%) had microfilariae. There were significant differences between communities in microfilariae prevalence and intensity of infection (P<0.05). Sex infection was similar in males (26.8%) and females (26.9%); whereas farmers (46.6%) and fishermen (28.4%) were more affected than people in other occupations. The proportion of infected persons increased with age coinciding with the period when most clinical signs manifest. A significant proportion of the 889 persons with positive microfilariae skin biopsy had musculoskeletal pain (57.1%). Thirty-four (47.2%) of the 72 epileptics identified had positive skin biopsy in addition to other manifestations. The present findings show that onchocerciasis is a public health problem in the area. The use of ivermectin has reduced the incidence of the disease when compared with data from the pre-ivermectin era. This shows that Community Directed Treatment with Ivermectin (CDTI) campaign is successful and should be sustained until onchocerciasis is eliminated as a public health problem in the area.