Integrated control of juvenile Ixodes scapularis parasitizing Peromyscus leucopus in residential settings in Connecticut, United States

Lyme disease continues to be the most common vector-borne disease in the United States with an estimated 330,000 human cases annually. In the eastern United States, the blacklegged tick, Ixodes scapularis, is the primary vector of the Lyme disease spirochete, Borrelia burgdorferi, and the white-footed mouse, Peromyscus leucopus, is a primary reservoir host. In four residential neighborhoods in Connecticut over three years, we tested the effectiveness of different low-toxicity integrated tick management approaches to control larval and nymphal I. scapularis parasitizing P. leucopus. Combinations of white-tailed deer, Odocoileus virginianus, reduction, broadcast application of the entomopathogenic fungus Metarhizium anisopliae, and distribution of fipronil-based rodent-targeted bait boxes were evaluated against an experimental control. Deer reduction with no other intervention likely forced juvenile I. scapularis to obtain blood meals from available reservoir hosts, resulting in increased exposure of P. leucopus to B. burgdorferi compared to control sites. The M. anisopliae/bait box and the deer reduction/M. anisopliae/bait box treatment combinations resulted in 94% and 85% reductions in larvae parasitizing P. leucopus that tested positive for B. burgdorferi, respectively, compared to control. Deer reduction alone resulted in only a 3% reduction, likely because parasitizing juvenile I. scapularis were not targeted by bait box-delivered fipronil. Unless there is community support to reduce and maintain deer at very low densities (<5 deer/km2), it is clear that a combination of M. anisopliae/fipronil-based bait boxes offers an effective, localized, low-toxicity option for reducing I. scapularis parasitizing P. leucopus without complications from host switching.