Egg output of Heligmosomoides polygyrus (Nematospiroides dubius) in mice infected once only.

Three experiments were carried out with the aim of knowing variations in egg production of Heligmosomoides polygyrus female worms in mice infected once only. The first experiment allowed definition of egg production cycle. A steep decrease in number of eggs laid was shown when worms had been implanted for more than 40 days. The cause of this decrease was investigated in the second experiment and in particular a possible elimination of a part of worm population was tested. Results showed that during 114 days at least the size of this population was stable. Therefore the decrease in egg production was rather to be put in relation with an ageing process of worms or as host's reaction. Results of the third experiment showed effect of the size of worm population on the individual fecundity of one female: the larger number of worms became the smaller was the fecundity. The main consequence of this reduction was a stabilization of total number of eggs laid by the whole parasite population beyond a certain number of worms (about 200 H. polygyrus adult stages).