Small Mammals

MouseThe first attempt to employ a host-targeted approach involved the distribution of permethrin-treated cotton in cardboard tubes, commercially available under the trade name Damminix, in wooded areas to control immature blacklegged ticks on white-footed mice. Separate spring and summer applications are required. The premise of this approach is that mice become self-treated with the acaricide after harvesting the cotton for use as nesting material and that immature ticks on mice and in mouse nests will be killed, ultimately reducing the number of host-seeking nymphs and transmission risk. Early studies in Massachusetts showed significant reduction of tick burdens on mice and the number of questing ticks within the treatment area. However, subsequent research in Connecticut and New York reported no difference in the number of host-seeking nymphs and adults between treated and untreated areas after several years of use and concluded that the reduction of tick burdens on mice was insufficient to reduce the risk of human-tick encounters. These conflicting results may be explained by differences in the availability of alternate nesting materials and/or the diversity, composition, and abundance of hosts.

Bait BoxIn the mid-1990s, the Centers for Disease Control and Prevention, Bayer Environmental Sciences (formerly Aventis Environmental Sciences), and scientists from several states developed and tested a bait box technology that targets certain small mammal hosts of immature blacklegged ticks. The child-proof bait box consists of 2 entry portals and a central corridor that leads to an overhanging acaricide-treated wick at the entrance to the paired bait chambers. Initial laboratory bioassays showed that the active ingredient fipronil killed immature blacklegged ticks for over 42 days following a single treatment. Early field studies in Connecticut resulted in a significant reduction of tick burdens on mice during the first year of deployment and reduction in the number of host-seeking nymphs and adults after the second year. This technology also interrupts the natural tick-mouse transmission cycle of Lyme disease spirochetes by killing the majority of spirochete-infected blacklegged tick nymphs before transmission can occur. Subsequent testing in New Jersey has shown over 93% reduction of nymphal and larval blacklegged tick burdens on target small mammals following separate deployments in spring and summer. By the second year of treatment, the level of control of host-seeking nymphs and larvae exceeded 86% and 90%, respectively. The bait box technology is commercially available under the trade name Maxforce Tick Management System.

Although the bait boxes appear to provide more consistent and reliable control, both rodent-targeted technologies share common limitations. Both techniques are considerably more expensive than habitat-targeted approaches by virtue of increased product and labor costs. Both technologies require manual deployment and retrieval of the product during each treatment period. Efficacy of rodent-targeted approaches is also affected by the diversity and composition of the small mammal community. Since the blacklegged tick lacks host specificity, an abundance of hosts that are not treated by these products will negatively impact efficacy. For example, the Eastern gray squirrel, Sciurus carolinensis, an important host of immature blacklegged ticks that is often quite abundant in residential environments, is not treated by either device. Damminix, for example, appears to be effective only in habitats dominated by white-footed mice. Finally, the efficacy of both technologies is limited to only those tick species whose immature stages feed on small mammals. Consequently, reduction of lone star ticks, which feed primarily on deer in all active stages, will not be achieved by the sole use of these rodent-targeted technologies.