Clinical, parasitological and serological studies on onchocerciasis in the Yemen Arab Republic.

Dermatological symptoms of onchocerciasis and microfilaria densities in the skin were studied in 108 infected persons in the Governorate of Taizz, and the levels of antifilarial antibodies and IgA, IgE, IgG, and IgM were determined in 75 of them. Predominantly in old men the generalized form of the disease was observed, which is characterized by symmetrical, mostly atrophic skin lesions, rather high microfilaria densities at various sites of the body and the presence of diagnostically unequivocal levels of antifilarial antibodies. In younger men, children and women of various age groups a localized form was observed, of which the typical features are: an intensely itching, mostly asymmetrical, well circumscribed onchodermatitis with or without oedema, pachydermia and darkening of the skin; considerable enlargement of several local lymph nodes; very or extremely low microfilaria density; the microfilariae are mostly restricted to the area of the skin lesion; manifestation of the microfilariae by a clear papular Mazzotti reaction after the application of microfilaricidal drugs; and diagnostically utilizable levels of antifilarial antibodies. The localized form can develop into the generalized form during later years. Intermediate and so far undefined forms, among which indeterminate forms may exist, are also seen. Patients with severe localized onchocerciasis demonstrated significantly higher antifilarial antibody levels than other infected persons. As a characteristic feature of onchocerciasis in the Yemen, onchocercomata were frequently found over the muscles of the calf, thigh and forearm distant from prominent bones. Onchocerciasis is endemic in all major wadis with permanent, westward flowing streams at altitudes of 300-1200 m between the southern Wadi Ghail and Wadi Surdud in the north and in some of their tributaries.