Intradermal Reactions to Schistosome and Filaria Antigens in Patients before and after Treatment of the Parasitic Infections

José Oliver-González Department of Microbiology, School of Medicine and School of Tropical Medicine, San Juan, Puerto Rico

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Summary

Individuals infected with Schistosoma mansoni were skin-tested with extracts of (1) dry and powdered cercariae of S. mansoni; and (2) dry and powdered adult Fasciola hepatica and Pneumoneces medioplexus. The skin tests were performed before treatment and for prolonged periods of time up to four years after treatment of the parasitic infection.

Using the cercarial antigen, the reactions were positive in above 90 per cent of the patients in all instances both before and after treatment. With the antigens from Fasciola hepatica and Pneumoneces medioplexus the percentage of positive reactions diminished greatly after treatment. The schistosome ova in the liver and other organs may continue to sensitize the host for short periods of time after death of the adult worms as a result of treatment. Also, positive intradermal reactions may be due to infection with a small number of adult worms which can not be detected by fecal or biopsy examinations.

Individuals with circulating microfilariae of Wuchereria bancrofti were skin-tested with antigen from Dirofilaria immitis and Litomosoides carinii and with antigen prepared from concentrated microfilariae. Positive reactions to the three types of antigen were observed in over 90 per cent of the individuals tested before as well as two years after treatment.

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