The activities of selected enzymes of carbohydrate metabolism were measured in tetrathyridia of Mesocestoides corti and in adult females and males of Heterakis spumosa. When the species were compared, only lactate dehydrogenase and phosphoenolphyruvate carboxykinase activities were considerably higher in M. corti. Activities of other enzymes were higher in H. spumosa, with malate dehydrogenase activity being considerable so. In H. spumosa, enzyme activity was higher, and succinate dehydrogenase markedly so in males, when compared with females. Tetrathyridia aged 170 and 210 days show relatively stable malate and lactate dehydrogenase activities, and mice of ICR and BALB/c strains are suitable for the maintenance of tetrathyridia.

This study describes the effects of testosterone (Te) on the intestinal nematode Heterakis spumosa in mice. The course of Heterakis infections 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 of Heterakis eggs 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 of Heterakis in 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 L4 larvae 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. (L2 larvae) 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 of Heterakis, i.e. hatching in the small intestine and final settling of L2 larvae in the upper colon are independent of Te. Also, Te does not affect motility and even slightly reduces the fecundity of adult female worms in vitro. Our data suggest that Te and/or Te-metabolites and/or Te-induced host factor(s) accelerate the development and growth of H. spumosa and favour the survival of Heterakis in the colon of mice.