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



Immediate hypersensitivity (IHS) and delayed hypersensitivity (DHS) responses to intradermal injection of adult worm and cercarial antigens were evaluated for over 700 African residents of Uganda, an area endemic for schistosomiasis mansoni. Current and former residents of areas of high and low endemicity were tested. Biopsies from 6 individuals with DHS and 2 with IHS but no DHS were examined histologically. The sensitivity of the IHS test with adult worm antigen was high (87–95%), and this antigen showed higher sensitivity than cercarial antigen in infected women and children. Specificity of the IHS test, defined as the per cent of IHS responders with eggs in a single stool examination, was low, ranging from 38% in children to 48% in adults for adult worm antigen. Histology and time course of appearance of DHS reactions were similar to reactions of cellular hypersensitivity to other antigens. Biopsies from DHS reactions showed perivascular infiltration of mononuclear cells which increased in intensity from 24 to 48 hours. DHS responses were less frequently encountered than IHS responses; though most subjects with DHS also had IHS, DHS was present alone in 12% of late responders. Size distribution of DHS response areas approximated log normal distribution; mean log response areas of adult males were significantly larger than corresponding reactions in females or children. An area of 0.6 cm was accepted as an adequate criterion of positive DHS response; selection of smaller areas to distinguish negative from positive reactions caused some increase in sensitivity, but in most cases a drop in specificity. The DHS test was not an indicator of the number of eggs in the stool at the time of testing. The sensitivity of the DHS test was low, ranging from 29% in infected adult females to 59% in adult males. Combined use of the IHS and DHS tests improved specificity of the intradermal test markedly in children but only slightly in adults. The utility of the DHS intradermal test in diagnosis of schistosomiasis seems limited. Other possible uses of DHS testing in schistosomiasis are mentioned.


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