A study of onchocerciasis with severe skin and eye lesions in a hyperendemic zone in the forest of southwestern Cameroon: clinical, parasitologic, and entomologic findings.

Prior to the initiation of an onchocerciasis control program based on the mass administration of ivermectin in the rain forest of southwestern Cameroon, a preliminary baseline study of the area was conducted. The results of this study showed that onchocerciasis was hyperendemic in the area. Skin symptoms and signs were observed including pruritus (67.4% of the population examined), onchocerca nodules (51.6%), skin depigmentation (18.5%), and hanging groins (5.7%). Except for pruritus, the prevalence of these symptoms increased with age. Of the eyes examined, 44.9% had microfilariae in the anterior chamber, 33.5% had choroidoretinitis, 28.0% had punctate keratitis, 8.3% had papillary abnormalities, and 3.6% had sclerosing keratitis. Vision in 10.5% of the eyes examined was classified as blind or very poor (visual acuity = 0-0.10), in 15.7% as poor (visual acuity = 0.11-0.39), and in 73.8% as good (visual acuity = 0.4-1.00). Unlike previous reports that have linked serious ocular damage mainly to savanna onchocerciasis, the present study showed that forest onchocerciasis also caused significant ocular pathology, including blindness. Parasitologically, positive skin snips were recorded for 92.7% of the persons examined, with both sexes being equally infected. The parasite load, expressed as the geometric mean number of microfilariae per skin snip, was 53.6, and was much higher in males than in females. The flv vector, Simulium squamosum, had a high infection rate of 7.5% infective females in Bakumba and 6.8% infective females in Ngbandi, the two fly-catching points. The transmission potential was 266 infective larvae per person per month in Bakumba and 189 in Ngbandi.