Function of the Thyroid and the Host-Parasite Relation in Murine Schistosomiasis Mansoni

Abstract

The effect of altered thyroid function on the host-parasite relation in murine hepatosplenic schistosomiasis was investigated. Young Swiss mice were injected with ¹³¹I-Iabelled iodide; three weeks later they were subdivided randomly: one group received no further treatment, another received 2 µg of l-thyroxine, and the third received 15 µg of l-thyroxine twice weekly. Cercarial penetration was lower in the hypothyroid animals. The schistosomes in the hypothyroid animals were small, while those in the hyperthyroid animals were large, matured earlier, and produced more eggs. The granulomas developing around eggs injected into uninfected mice were small in the hypothyroid and large in the hyperthyroid animals. The inflammatory process was accelerated in the hyperthyroid and slowed in hypothyroid mice. With respect to hepatosplenic disease, the hypothyroid animals had the least change during the acute stages, but underwent an exacerbation in the chronic stages, while the disease in the hyperthyroid mice was ameliorating. None of the hypothyroid animals died in the first 16 weeks after infection, while the mortality in the other three groups varied from 25% to 40%. Alterations in thyroid state had profound effects on both the worms and the host's reaction to them.