Document Type



The effect of race on the development of severe schistosomiasis was investigated. The proportion of Whites, Mulattoes and Blacks was compared in patients with mild, moderate and severe schistosomiasis and in controls. Another group of schistosomiasis patients was followed for six years to study the evolution of the disease as a function of race. In both studies there was strong evidence for a greater resistance in Blacks to develop severe schistosomiasis while infection rates were similar in both races and in Mulattoes. The possible biological causes for resistance to develop severe schistosomiasis are discussed.