Studies on Immunity to Schistosoma Mansoni—II. The Circumoval Precipitin Reaction to S. Mansoni in Mice Treated with Stibophen

Abstract

Summary 1. Mice infected with Schistosoma mansoni for 70 days were treated with stibophen (Fuadin®) given intramuscularly, at a dosage of 10.2 mg per kilo, and administered daily over 5 days a week, for periods up to 280 days. Another group of untreated mice was left as controls. 2. The animals were sacrificed at regular intervals, the blood serum was tested for circumoval precipitins and the liver and intestine examined microscopically for eggs. 3. The liver and intestine of the untreated mice which lived up to 210 days after exposure to cercariae contained live eggs. The circumoval test was positive in all animals tested. 4. Positive circumoval precipitin tests were observed in the treated mice up to the 210th day of therapy, while negative tests were observed in the serum from mice past the 210th day of therapy. The liver and intestine became negative for embryonated and intact schistosome eggs, as determined by examination of tissue sections and compressed slices of fresh tissues beginning on the 210th day of therapy. The negativity of the circumoval test is therefore substantiated by the absence of embryonated and intact eggs from the tissues. 5. Since the circumoval precipitin reaction becomes negative at a certain time after or during prolonged therapy, it is suggested that the test may be of value in determining extermination of infection as a result of therapy, or due to other factors.