1.Subcutaneous nodules were palpated on 469 or 19.4 per cent of 2,423 laborers on the Firestone Plantation in Liberia. Approximately 90 per cent of these nodules were located in the pelvic region.
2.Microfilariae were demonstrated in 278 or 39.9 per cent of 696 Africans examined by both skin biopsy and scarification smears, which was higher than any single method of diagnosis employed.
3.Nodules containing O. volvulus occurred in a significant number of cases in the absence of demonstrable microfilariae on skin biopsy and scarification smears. The highest prevalence of onchocerciasis was demonstrated by combining skin biopsies, scarification smears, and palpation for nodules.
4.Microfilariae of W. bancrofti and A. perstans occasionally occurred in skin biopsies, especially in patients from the Coast where the prevalence of wuchereriasis was much higher.
5.Small nebulae and other minute corneal opacities occurred with greater frequency among individuals with onchocerciasis than in those without this infection. Ocular pathology attributable to this disease was not severe enough nor common enough in the groups examined in Liberia to make it a public health problem. Onchocerciasis should, however, be considered in the differential diagnosis of ocular pathology in the individual case.
6.Onchocerciasis was most common in the tribes from the interior of Liberia. The Kpelle, Gola, Mendi, and Gbandi tribes especially had a high rate of infection, whereas, among the Kru, Vai, and coastal Bassas it was much lower.
National Institutes of Health, National Microbiological Institute, Laboratory of Tropical Diseases, Bethesda, Maryland.
Medical Department, Firestone Plantations Co., Harbel, Liberia.