Foraging among feces: Food availability affects parasitism of Peromyscus leucopus by Baylisascaris procyonis

Baylisascaris procyonis is a parasitic nematode of raccoons (Procyon lotor) capable of infecting many species of small vertebrates as intermediate hos ts. In these hosts, migrating larvae often cause fatal or severe central ne rvous system (CNS) disease. Previous research suggested that intermediate h osts become infected with B. procyonis while visiting raccoon lat-tines. We tested effects of ambient availability of food and duration of exposure on dynamics of transmission of B. procyonis to white-footed mice (Peromyscus leucopus) in a factorial design within enclosures containing artificially c onstructed raccoon latrines. Fifty percent of experimental mice acquired B. procyonis infections and 43% of infected mice developed CNS disease. Visit ation to latrines was marginally greater (P = 0.095) for mice subjected to low availability of ambient food. The mean number of larvae per mouse was g reater (P = 0.001) in low food group after exposures of 14-28 days. Probabi lity of infection varied predictably as a function of duration of exposure (P = 0.005), and probability of CNS disease varied predictably as a functio n of level of ambient food available (P = 0.023). We conclude that transmis sion of B. procyonis occurs at raccoon latrines and that increased visitati on to latrines and duration of residence in close proximity to a latrine, b oth increase probability of mortality due to CNS disease, especially when i ndividuals are stressed by reduced resources or poor habitat.