Entomological Correlates of Babesia microti Prevalence in an Area Where Ixodes scapularis (Acari: Ixodidae) Is Endemic

Zoonotic prevalence of Babesia microti</it> Franca piroplasms infecting white-footed mice, Peromyscus leucopus</it> Rafinesque, was determined at 34 sites in Rhode Island where nymphal blacklegged tick, Ixodes scapularis</it> Say, densities ranged from low to hyperabundant (1.7–525.3 nymphs per hour of flagging). Babesia</it> was only detected at sites where tick abundance was moderate to high (>20 nymphs per hour of flagging) and appeared to exhibit a clumped distribution. Where B. microti</it> was detected, the mean number of nymphal ticks collected per hour of flagging was 229.2 compared with a mean of 40.1 at sites where Babesia</it> was not detected. By combining the spatial occurrence of Babesia</it> with a tick density database in a geographic information system, it may be possible to predict the pattern of zoonotic and human infection with B. microti</it>.