The effects of time and temperature of storage on the infectivity of third-stage larvae of Heligmosomoides polygyrus (= Nematospiroides dubius). 2. Studies on the fecundity of female worms as a function of the infectivity of the third-stage larvae.

In this study we examined the effect of infectivity of third-stage larvae on the fecundity of H. polygyrus female worms. Groups of 10 mice were infected with third-stage larvae which had been stored for different lengths of time at 22 degrees C. Results showed that the number of eggs laid by one female worm increased when the worm burden was smaller and decreased with a greater worm burden. Also, the egg-output of female worms growing in a similar population varied according to the level of infectivity of the larvae, with a low infectivity resulting in greater fecundity and vice versa. These results may explain the variations in egg-output which are recorded at different times of the year from the parasites of grazing animals. If this phenomenon is confirmed in other species of parasites, it will be important for epidemiological studies.