Effect of gonadectomy and gonadal hormones on singly established Hymenolepis diminuta in rats

Abstract

The effects of gonadectomy and gonadal hormones on singly-established H. diminuta in rats on “complete” and “deficient” diets have been studied by means of estimations of the number of eggs eliminated by the parasite per 24-hour periods over varying intervals of time. A decline in the number of eggs of H. diminuta eliminated per 24 hours over a period of 3 months was observed in castrated male rats fed a “complete” diet which was comparable to the effects observed in normal male hosts on a “deficient” diet. Castrated males fed a “deficient” diet, however, exhibited a decline in the numbers of eggs of this cestode eliminated which was comparable to that observed in normal female hosts on a “deficient” diet. Testosterone and progesterone, administered at the rate of 1 mg per day, restored egg output to approximately normal levels in castrated male hosts. Testosterone was also similarly effective in normal female rats on “deficient” diet, but progesterone was ineffective. Chorionic gonadotropin raised the egg output of H. diminuta in normal male and female rats on “deficient” diet but not in gonadectomized hosts. A stimulation of testosterone production is postulated as a possible mechanism in the case of normal male rats and possibly the production of estrogen in the normal female hosts. Accidental concurrent infections with a few Moniliformis dubius had no evident effect on egg production of H. diminuta. These acanthocephalans were lost quickly from hosts on “deficient” diet.