oa South African Medical Journal - Skin tests for schistosomiasis



The literature on skin tests for bilharziasis is reviewed. A skin test antigen prepared from Fasciola hepatica is descriptionbed. Positive results were obtained in 34 out of 35 proved adult cases. One case of onchocercus infection gave a false positive reaction. A high percentage of false negative reactions in children was attributed to the short duration of infection. This antigen completely lost its potency after storage for four years in a refrigerator. A cercarial skin test antigen is descriptionbed. Out of 28 proved cases (adult and children) 26 gave positive results and two gave doubtful reactions. Two out of five cases of Ascaris infection, one out of two cases of T. saginata infection and one case of Ankylostoma infection gave doubtful reactions. A case with a mixed infection of Ankylostoma, Ascaris, and Trichuris gave a positive reaction and one case of cysticercosis gave a negative reaction. This antigen has retained its potency for three years in a refrigerator and for six months at room temperature. Although the number of cases investigated is very small, it is sufficient to prove that the cercarial antigen skin test is an important aid in the diagnosis of bilharzia. The occasional false positive reaction does not detract from its value as a screen test in endemic areas and as an aid in the diagnosis of cases with symptoms and signs suggestive of bilharzia and in whom no ova can be demonstrated.


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