Within-host dynamics of Trichinella spiralis predict persistent parasite transmission in rat populations

Trichinella spiralis is transmitted and maintained in both a domestic and sylvatic cycle, whereby rats contribute to the spread of T. spiralis from domestic to sylvatic animals and vice versa. As a model for T. spiralis transmission in wildlife, we studied the potential of rats to act as a reservoir species for T. spiralis, by assessing experimentally its within-host infection dynamics, and simulating the between-host dynamics by a Monte Carlo approach. The distribution of parasite burden in individual rats is mathematically defined by roots of the dose response equation intersecting with the diagonal. In simulated between-host dynamics, up to 10⁴ events of uninterrupted parasite transmission were observed. Histograms of parasite burdens per individual rat matched closely with the mixture of two gamma distributions, which were derived from the within-host infection dynamics. In conclusion, T. spiralis transmission persists in a population of rats when they cannibalize their own species. Rats should be included in the minimal set of wildlife species that maintain the life cycle of T. spiralis.