Demography of botfly (Cuterebra fontinella) parasitism in whitefooted mice (Peromyscus leucopus) in Kansas.

Botflies (Diptera: Cuterebra sp.) are widely distributed and seasonally abundant parasites of small mammals in North America. To assess their effect on rodent survival, we studied the demography of botfly parasitism on small mammals in northeastern Kansas during 1995–1999. Additional comparisons on botflies parasitizing small mammals were made to a nearby old-field grid where mark–recapture studies continued from 1975 to 2003. White-footed mice, Peromyscus leucopus, were infected by botfly larvae (Cuterebra fontinella) each year during our study. The period of infection for P. leucopus was June–December, with the highest proportion of mice infected in July and August. A smaller, second peak of infection in October and November indicated that C. fontinella reproduced bimodally at this latitude with distinct summer and autumn population peaks. During the botfly seasons of the 5 years, 140 (23.3%) of 602 P. leucopus captured were infected. The percentages of individuals infected during 1995, 1996, 1997, and 1999 were not significantly different (22.4%, 17.3%, 17.1%, and 22.7%, respectively). However, in 1998, 32.4% individuals were infected with a higher incidence of multiple infections and a greater number of botfly larvae per host. Nearly half (47%) of the infected individuals caught in 1998 had infections in both summer and autumn, compared with 25% during the 1995–1997 seasons. In 1999, 63% of infected mice had at least a 2nd infection during the autumn. For all 5 years, 82%, 14%, and 4% of the infected mice had one, two, or three botflies, respectively. In 1998, 24% of the infected mice carried two or more botflies at one time, compared to 14% from 1995–1997 and 11% in 1999. Overall 94% of the infected mice were adults, with no differences between sexes. The variation seen in the prevalence of botfly parasitism of whitefooted mice correlates to yearly weather fluctuations. Other demographic aspects of the infected mice, such as sex ratio, age, and longevity of those infected, did not change year to year. Our data suggest that infection with Cuterebra has little negative or positive impact upon populations of white-footed mice. [ABSTRACT FROM AUTHOR]