Onchocerca Volvulus infection in Sierra Leone: relation between prevalence, intensity of infection, and ocular problems in a 'forest' region.

A two-year longitudinal study carried out in five villages in a forest region of Gorama Chiefdom, Kono District, Sierra Leone, revealed that infection with Onchocerca volvulus was hyperendemic, the overall rate of infection being 61.6%. Prevalence rose from 28.6% in the 1-5-year age group, peaking among the 21-30-year age group (82.5%) and then levelling off. The intensity of infection though low, peaked in the 31-40-year-old males and in the 41-50-year-old female cohorts. The iliac crest was more sensitive for microfilarial (mf) recovery than the shoulder and the outer canthus. The majority of the nodules were located in the pelvic region. Microfilariae invasion of the eye was low, with low anterior chamber lesions but high posterior chamber lesions comprising mainly optic atrophy and choroidoretinitis. The rate of blindness was 1.6%, ocular onchocerciasis being the leading cause of blindness followed by cornea opacities.