Effects of Babesia microti infection on feeding pattern, engorged body weight, and molting rate of immature Ixodes scapularis (Acari: Ixodidae).

Effects of Babesia microti Franca on the pattern of feeding time, the body weight of engorged ticks, and the molting rate of the blacklegged tick, Ixodes scapularis Say, were determined. Using the Syrian golden hamster, Mesocricetus auratus (Waterhouse), as an animal model, we found no significant differences in patterns of feeding time determined for both larvae and nymphs that fed on B. microti-infected and uninfected hamsters. However, an infection of B. microti in hamsters delayed engorgement of the ticks. The presence of B. microti had no adverse effects on the body weight of engorged ticks. The mean body weight of groups of 5 engorged larvae fed on infected hamsters was not significantly different from that on uninfected hamsters. The mean body weight of individual nymphs that fed on infected hosts was significantly higher than that on uninfected hosts. Larvae fed on infected hamsters molted in greater numbers than those fed on uninfected hamsters. However, there was no significant difference in molting rates of nymphs derived from infected and uninfected hamsters. In addition, greater body weights and higher molting rates were observed in both larvae and nymphs that fed on uninfected white-footed mice, Peromyscus leucopus Rafinesque, compared with those on uninfected hamsters. Nymphs fed on mice spent a significantly longer time achieving repletion than those on uninfected hamsters. We suggest a mutualistic relationship in the interactions between B. microti and I. scapularis. This mutualism may potentially enhance the long-term coexistence and survival of both species. Furthermore, we suggest that the pattern of feeding time, the body weight of engorged ticks, and the molting rate of immature I. scapularis are host-dependent.