Effects of testosterone onHeterakis spumosainfections in mice

Abstract

SUMMARYThis study describes the effects of testosterone (Te) on the intestinal nematodeHeterakis spumosain mice. The course ofHeterakisinfections is apparently under Te-control. At high circulating Te-levels as occurring in intact males, Te-treated females, and Te-treated castrated males, the period of release ofHeterakiseggs in mouse faeces is greatly extended and the number of eggs released per unit time is markedly elevated in comparison to low Te-levels, as found in untreated females and castrated male mice. Also, the onset of the patent period occurs earlier in Te-treated mice. Testosterone also accelerates development and growth of both female and male worms ofHeterakisin mice. Thus, young adult male worms can be observed in the upper colon of Te-treated castrated male mice on day 21 post-infection (p. i.), whereas, at that time, only L4larvae are present in Te-untreated male castrates. Testosterone also favours the survival of nematodes in hosts. In untreated male castrates, the number of worms present on day 7 p.i. (L2larvae) is approximately two thirds higher than that found on day 21 p.i. However, such a reduction in the number of worms does not occur in Te-treated castrated mice during the same period of time. The early phases of the life-cycle ofHeterakis, i.e. hatching in the small intestine and final settling of L2larvae in the upper colon are independent of Te. Also, Te does not affect motility and even slightly reduces the fecundity of adult female wormsin vitro. Our data suggest that Te and/or Te-metabolites and/or Te-induced host factor(s) accelerate the development and growth ofH. spumosaand favour the survival ofHeterakisin the colon of mice.