[Aspects of the development of ocular onchocerciasis in West-Africa after three years of simulium control (authors transl)].

In four rural West-African communities with different degrees of ocular affection the development of ocular onchocerciasis has been evaluated after three years of vector control. In the area of a successful disruption of the transmission the population with a slight degree of ocular onchocerciasis before control operations started, did not show an aggravation of the lesions. In those groups severely affected at the beginning of vector control the lesions showed no progression in the majority of the cases. The diminuition of the ocular parasite load, resulting from the reduced transmission, appears to be an important factor in the change of the incidence of blindness and severe ocular lesions attributable to onchocerciasis. Contrary to this the aggravation of ocular lesions was found to be more severe in a community situated in the area reinvaded by the vector than in those that did not experience a reinvasion of the fly.