Infection with pinworms (Syphacia obvelata) does not affect the plasma corticosterone concentration in male, nonpregnant female, and pregnant female rats.

Abstract

Pinworm infections are common in rodent colonies, but the effect of pinworms on the host hypothalamic-pituitary-adrenal (HPA) axis had not been investigated. Other parasites stimulate, inhibit, or have no effect on the HPA axis of their hosts. We studied the effect of Syphacia obvelata infection on plasma corticosterone concentrations in Sprague-Dawley rats. Blood samples were taken from male, female, and pregnant rats during an active infection, when all 21 rats examined harbored worms, and after 4 weeks of treatment with piperazine and ivermectin, when only 2 of the 23 rats examined harbored worms. Plasma corticosterone concentration was measured by radioimmunoassay, and all pinworms in the cecum and colon were counted. Plasma corticosterone concentration did not differ between infected and uninfected rats in any group of rats. Pinworms were much more abundant in pregnant rats than in male or nonpregnant female animals. Corticosterone was highest in pregnant females and lowest in males. In conclusion, infection with S. obvelata did not affect plasma corticosterone concentration in male, female, or pregnant rats, suggesting that such an infection does not invalidate studies of the HPA axis in these animals.