I. ONCHOCERCIASIS

Onchocerciasis (blinding filariasis, river blindness), is caused by a small worm which causes nodules in the skin, usually on the head and trunk. Hundreds of thousands of tiny embryos (microfilariae) are released from the nodules into the surrounding tissues. When these microfilariae migrate to the eye, impaired vision and frequently total blindness result. The disease is transmitted by several species of gnats (Simulium) which breed in rapidly flowing streams-hence, the name "river blindness."

Onchocerciasis affects nearly 20 million people in Africa, Central and South America, involving up to 80 to 100 percent of the population in limited areas. In Central America, the disease occurs on the Pacific slopes of 3 states in Guatemala and 2 in Mexico. In South America, it is localized in the north-central portion of Venezuela. In Africa, onchocerciasis extends from Sierra Leone and Liberia southward through Ghana, Nigeria, and the Cameroons to the Belgian Congo; then east across central Africa to Uganda, Kenya, Nyasaland, and Tanganyika with a northward extension up through Sudan and western Ethiopia.

Through the use of new drugs in mass campaigns, considerable progress has been made in the control of the disease in Africa and the Americas, and surgery has helped reduce its damaging effects in Guatemala and Mexico. Insecticide campaigns to exterminate the disease-carrying flies have been initiated in Kenya and other parts of Africa with some indication of success.

J. AFRICAN SLEEPING SICKNESS

Sleeping sickness (trypanosomiasis) is prevalent in most of Africa, south of the Sahara, except the southern part of the Union of South Africa. It is a particularly virulent disease, transmitted by the tsetse fly, which numbers many people among its victims. The forms found in man also affect animals, particularly cattle; certain other species affect animals only.

The overall effect of sleeping sickness among the rural population and their domestic animals constitutes one of the greatest barriers to African economic progress. It so debilitates and kills the infected individual and his stock that productivity is seriously diminished. Large segments of the population have tended to migrate to areas relatively free of the tsetse fly. This, in turn, has served to overcrowd areas having an already low per capita agricultural yield. Populations are deprived of needed animal protein in the diet, of the service of draft animals for work, and of fertilizer needed to cultivate the fields.

Formerly, sleeping sickness was almost inevitably fatal. Now, however, the use of drugs makes possible a cure in the early stages. Modern chemoprophylaxis and public health measures have reduced the incidence of the human disease in many endemic areas. In other regions the use of residual insecticides has reduced, and sometimes eradicated, the tsetse fly. Despite these gains, the toll from sleeping sickness is high.