Ocular onchocerciasis.

ONCHOCERCIASIS is caused by infection with the adult filarial worm Onchocerca volvulus; the microfilariae of this worm develop in the body of man and sometimes penetrate the tissues of the eye where they set up pathological changes leading to blindness; embryos may also be found in the skin, in lymph glands, in the fluid of hydroceles, and in effusions into joints. The disease has been reported from central America, and from scattered areas in equatorial Africa in a vast belt of territory which extends from latitude 150 N. to 200 S. (Hughes, 1949); in W. Africa the distribution closely follows that of the fast flowing rivers and streams in which the vector, Simulium damnosum, breeds. This association with rivers is known to many Africans. The Moshi tribe of the French Upper Volta have a saying recently translated by Puyelo and Holstein (1950): La proximite des grandes rivieres ronge les yeux. Hughes noted that Gold Coast fishermen have long blamed the foam on the rapids of the River Volta for their high incidence of blindness. The incidence of eye complications, based largely on figures for incidence of blindness, appears to vary considerably in different areas: in a recent survey of some 88,000 inhabitants of the French Upper Volta district, Puyelo and Holstein reported blindness rates up to 35 per cent. in one village; Hissette (1932) found 15 per cent. blind in a village in the Belgian Congo; Waddy (1949) reported 10 per cent. in villages in the Northern Territories of the Gold Coast; Strong (1934) found that 5 per cent. among his Guatemala cases of onchocerciasis had " eye disturbances ". At the other end of the scale, Blacklock (1926) in Sierra Leone and Sharp (1927) in the Cameroons found no associated blindness with onchocerciasis. The total extent of the sociological problem of onchocerciasis cannot at present be assessqd, but there is no doubt that it is considerable; the incapacitating effect of the eye lesions, which can be inferred from the published blindness rates in some districts, is tragic, and the general lesions in the skin and other organs cause serious distress to the inhabitants of highly infected areas. Ridley (1950) has pointed out that the possibility that ocular onchocerciasis is the cause of obscure ophthalmic conditions in