A skin test evaluation for schistosomiasis was made on a citrus estate located near Salisbury, Southern Rhodesia. One hundred fifty-five Bantu children, 6–13 years of age (100 males and 55 females), were tested. In this group, 142 (92%) were found to be infected with either Schistosoma mansoni or S. haematobium on examination of one urine and one stool specimen. The group was tested with antigens prepared from adult worms of S. mansoni administered by needle and syringe. In addition, the same antigen was administered with a foot-powered hypodermic jet injection apparatus equipped with an intradermal head. Antigens prepared from adult worms of S. japonicum and larvae of Trichinella spiralis were administered and tested by needle and syringe in the skin. Control antigen consisted of buffered saline with merthiolate.
The average wheal area obtained in the group with the control antigen was 0.6 cm2; with the S. mansoni antigen (needle and syringe) 3.0 cm2; with the S. mansoni antigen (jet injector) 2.5 cm2; with the S. japonicum antigen 2.9 cm2; and with the T. spiralis antigen 0.8 cm2.
In the group, 25 were infected by S. haematobium, 50 by S. mansoni and 67 by both parasites. There was a significant difference in skin reactivity demonstrated by individuals infected with one or both parasites. There was no significant difference in the average size of the wheal area between S. mansoni and S. japonicum antigens. The S. mansoni antigen was, however, more sensitive than the S. japonicum antigen. Five of 142 infected individuals were false-negative with the S. mansoni antigen, whereas 10 of 142 were false-negative with the S. japonicum antigen.
The excretion of S. haematobium eggs in the urine over a one-hour period was measured. There was no correlation between the size of the wheal in the skin test and the hourly excretion of eggs.
Three individuals out of 88 tested with the T. spiralis antigen were positive with wheal areas of 1.4, 1.9 and 3.0 cm2. The serum of the individual with the 3.0 cm2 wheal area was tested for antibodies against T. spiralis and was found to be negative.
Eggs of S. mansoni were found in the urine of eight individuals, eggs of S. haematobium in the stools of two individuals and eggs of S. matheei in the urine of one individual. Of the 13 individuals negative by one urine or stool specimen, seven were positive by the skin test.
Communicable Disease Center, Public Health Service, U. S. Department of Health, Education and Welfare, Atlanta, Georgia 30333.
Division of Communicable Diseases, World Health Organization, Geneva, Switzerland.
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