The prevalence of onchocerciasis on selected divisions of the firestone rubber plantation, Harbel, Liberia

A survey for the prevalence of onchocerciasis was conducted on selected divisions of the Firestone Rubber Plantation, Harbel, Liberia, in November 1980. Divisions 19, 22, 23, and 36 are located in the north-central portion of the plantation, and were selected to complement transmission studies which were performed there in 1979 and 1980. Biopsy of the calf, iliac crest, and shoulder was done on a total of 583 individuals. No lateral difference in microfilarial density was observed. A prevalence of 80.8% was found. Prevalence appeared to be equal between the sexes, and to plateau above 35 years of age. Of those presenting positive skin biopsies, 20.2% had palpable onchocercomata. The geometric mean wet weight microfilarial density/mg of skin for the population sampled was 19. Onchocerciasis is considered hyperendemic in the Harbel area. Further investigations are warranted to define its dimensions in relation to clinical sequelae on the plantation.