Volume 23, Issue 2
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Intradermal tests for immediate hypersensitivity (IHS) and delayed hypersensitivity (DHS) to adult worm and cercarial antigens and stool examinations were carried out among residents of Uganda with different histories of exposure to . Among residents of a highly endemic village, eggs were found in the stools of 83% of adult males and children and 49% of adult females; DHS responses among infected individuals ranged from 30% in adult females to 64% in adult males. Stool egg counts did not increase significantly with longer residence among professional fishermen of the village, a group in which DHS reactions were common. In a survey of an area of low endemicity 11% of stools were found to contain eggs. DHS responses were less frequent than in the highly endemic area, reaching a peak of 43% among adult males with IHS (1 of 5 adult males with eggs in the stool had DHS). Among former residents of the highly endemic districts of West Nile, Madi, and Acholi currently living in a nonendemic city (Kampala) overt infections were generally less common and less intense than in residents of the highly endemic village, but DHS response patterns were strikingly similar in the 2 groups. DHS responses were retained in some individuals for up to 4 years in the absence of exposure to cercariae. In some immigrants from North America or Europe, apparently light and in some cases recent infections were found; DHS responses in this immigrant group were more frequent than might have been predicted on the basis of results in African residents of an area of low endemicity. DHS responses to schistosome antigen were found among 7% of residents of districts of Uganda not known to be endemic for . Findings in this investigation were consistent with the hypothesis that DHS response frequencies in groups from endemic areas are related to the frequency of past exposure to schistosome infection in the groups. The DHS response may prove to be of use in reconstructing past epidemiological conditions in groups, e.g., after population migrations or treatment programs. It was postulated that the high frequency of DHS responses among recent immigrants may have been influenced by lack of prenatally acquired or genetically determined tolerance to schistosome antigens or to occurrence of Jones-Mote type late reactions. The possible role of DHS in resistance to superinfection in schistosomiasis is considered.


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