SUMMARYWe analysed 3 independently collected datasets of fully censused helminth burdens in wood mice,Apodemus sylvaticus, testing thea priorihypothesis of Behnkeet al.(2005) that the presence of the intestinal nematodeHeligmosomoides polygyruspredisposes wood mice to carrying other species of helminths. In Portugal, mice carryingH. polygyrusshowed a higher prevalence of other helminths but the magnitude of the effect was seasonal. In Egham, mice withH. polygyrusshowed a higher prevalence of other helminth species, not confounded by other factors. In Malham Tarn, mice carryingH. polygyruswere more likely to be infected with other species, but only among older mice. Allowing for other factors, heavy residualH. polygyrusinfections carried more species of other helminths in both the Portugal and Egham data; species richness in Malham was too low to conduct a similar analysis, but asH. polygyrusworm burdens increased, so the prevalence of other helminths also increased. Our results support those of Behnkeet al.(2005), providing firm evidence that at the level of species richness a highly predictable element of co-infections in wood mice has now been defined: infection withH. polygyrushas detectable consequences for the susceptibility of wood mice to other intestinal helminth species.
Helminth species richness in wild wood mice,Apodemus sylvaticus, is enhanced by the presence of the intestinal nematodeHeligmosomoides polygyrus