Parasite density and the fecundity of Angiostrongylus cantonensis in rats.

The larval output of Angiostrongylus cantonensis at different initial densities in rats was examined throughout the reproductive life-span of the worms using a modified dilution technique. With an initial density of 2 worms the mean duration of larval output was 414.2 days. The output was at a level above 50000 larvae/female/day from 15 to 45 weeks after infection. The mean total output was 18.9 X 10(6) larvae/female. The larval output/female decreased with an increase in the worm burden and also with the passage of time after infection. The longevity of host rats also decreased with increasing worm density and many of the heavily infected rats died early during infection. These results suggest that worm density has an effect on the fecundity of this parasite, and that the effects may be due to fibrous changes in host lung tissue but not changes in the physiology of the worms. It is also suggested that density-dependent effects on fecundity play a role in the population dynamics of both the parasite and host as regulatory mechanisms in the field.