An experimental and theoretical study of the dynamics of a mouse-nematode (Heligmosomoides polygyrus) interaction

The population dynamics of outbred laboratory mice in indoor enclosures in the absence and presence of a naturally transmitted direct life-cycle nematode Heligmosomoides polygyrus Dujardin 1845 were reported previously. This manuscript presents further information on the age and sex structure of the populations, results of experiments designed to estimate the density-dependent effect of the parasite on host survival and reproduction, and a mathematical model of both uninfected and infected mouse populations. In the uninfected mouse population, survival of female mice was age- and density-independent, survival of male mice was age-dependent and density-independent, and recruitment was density-dependent. Independent experiments revealed that the parasite had no density-dependent effect on mouse reproduction, but had density-dependent effects on both acute and chronic survival of mice. An age-structured Leslie matrix model captured the exponential growth and plateau of the uninfected mouse population. Modification of the model to incorporate the effects of the parasite provided a good fit to the data from the infected populations, supporting the hypothesis that density-dependent effects of the parasite on host survival could lead to regulation of host abundance.