Physiological responses of deer mice (Peromyscus maniculatus) to infectionwith Capillaria hepatica (nematoda)

Negative effects due to infection have nor been documented for most natural host-parasite associations. I performed an infection experiment to measure the physiological consequences of infection by Capillaria hepatica in deer mice (Peromyscus maniculatus gracilis). Compared to their uninfected sibli ngs, infected mice displayed increased serum concentrations of alkaline pho sphatase and total proteins and reduced concentrations of albumin. Infected mice also had higher hematocrits and enlarged livers and spleens. There wa s no difference in swimming endurance between infected and control animals, possibly because mice did not perform at maximum aerobic capacity. Sex dif ferences in alkaline phosphatase and albumin levels suggest that females ar e more sensitive to similar burdens of C. hepatica. Different hematocrit re sponses between mice from 2 localities suggest that historical associations can lead to evolutionary change in pathophysiology caused by this nematode . Further experiments would reveal whether these disturbances lead to reduc tions in host fitness.