Experiments in the laboratory showed that abiotic and biotic factors can affect the frequency of infestations and expulsion of parasites. In order to analyse if there are such influences in a population of wild house mice, different samples (faeces, tape, Cryptosporidium-smear) were collected and examined for ecto- and endoparasites. Altogether 134 individuals were analysed and there were multiple samples from 42 animals (2 to 5 samples per mouse).
The results show that the significant differences in prevalence and expulsion rate according to age, gender or reproduction state which can be found often in laboratory studies could not be confirmed in this wild population. Also other factors such as the minimum and maximum temperature in the barn, the group size, the nest type or multiple infections had no significant effect.