Completion of Schistosoma mansoni life cycle in thyroidectomized rats and effects of thyroid hormone replacement therapy.

The survival and maturation of Schistosoma mansoni worms was analyzed in normal, thyroidectomized (Thyrox), and hormone-restored Thyrox rats. Restoration therapy was conducted with both T3 and T4; weight gain of treated rats was monitored to assess hormone-replacement efficacy. Worm yields, lengths, and sex-ratios were compared. Egg yields and the capacity of miracidia to hatch from eggs were also analyzed. The results of these studies support the conclusion that the sequence of steps leading to completion of the S. mansoni life cycle are operational in Thyrox rats. Hormone-treated Thyrox rats are restored to the nonpermissive status, although the worms isolated from these rats still differ in certain respects when compared to worms isolated from normal rats.