N. SCHISTOSOMIASIS

Schistosomiasis, involving an estimated 150 million persons in the tropics and subtropics, is a debilitating parasitic disease caused by several species of small worms, called blood flukes. The disease is most prevalent across tropical África, along the Mediterranean coast, in the Nile Valley (especially the Nile Delta), along the Yangtze River of the China mainland, in Japan and certain of the Philippine Islands, and in Puerto Rico, Venezuela, and Brazil in the Western Hemisphere.

Infection with these worms is acquired by penetration of aquatic larval forms through the skin. Various species of snails (mollusks) serve as intermediate hosts. The adult worms live in the smaller blood vessels of the intestine or the bladder and result in moderate to severe tissue damage in these areas, in the liver, and occasionally other parts of the body. Heavy infections result in emaciation, weakness, increased susceptibility to other infections, and even death.

Perpetuation of these infections depends upon contamination of water with fecal discharges and the availability of proper species of snails. The infection rate in any area can be regarded as a reliable index of the level of environmental sanitation.

Treatment is difficult, expensive, and not too effective so that control depends largely on snail eradication and education of the people. Newer molluscicides have been used in some areas with encouraging results. However, schistosomiasis, with its overall adverse effect on large segments of the population of certain countries, must be ranked as a world public health problem of major importance.

O. LEPROSY

The highest rates of infection occur in warm and humid climates associated with overcrowding and poverty. However, many of the preeminent factors affecting the distribution of leprosy remain undetermined. Racial factors seem to be of some significance. Europeans and Mongolians appear to be more susceptible to the severe form of the disease whereas darkly pigmented peoples seem prone to develop the mild form. Children appear to be especially susceptible. Possibly malnourishment and dietary deficiencies may favor its onset. Leprosy still remains an important health problem in many of the underdeveloped areas of the world. Estimates of the total number of cases in the world range from 2 to 12 million. Such a wide range is due, among other reasons, to the fact that early manifestations of the disease develop insidiously and may not be recognized for years. In most countries, measures are directed toward early diagnosis of the disease and prompt therapy, including the use of sulfones.