Oral fipronil formulations to control blacklegged ticks feeding on two host species: methods to prevent human lyme disease

Lyme disease is the leading vector-borne disease transmissible to humans in the United States. Control strategies directly targeting pathogen hosts (white-footed mice) and reproductive hosts (white-tailed deer) could markedly reduce pesticide application rates, reduce tick survivorship and reproduction, and subsequently reduce risk of human Borrelia burgdorferi infection. We developed a low dose fipronil bait, for oral consumption by small rodents such as white-footed mice, to control immature blood-feeding blacklegged ticks. Mice were presented fipronil bait under simulated field conditions. Mice were then manually infested with tick larvae. The results indicated that larvae blood-feeding on treated mice could be significantly controlled when mice were infested up to Day-15 post-exposure (24-hour bait exposure), and up to Day-35 post-exposure (168-hour bait exposure). A low dose fipronil feed, to control adult blacklegged ticks blood-feeding on white-tailed deer, is under development. Captive deer (Pennsylvania State University) were presented fipronil feed for 48-hours in a range finding study. Ticks were inserted into feeding capsules attached to each deer at Day-1 post-exposure. Results suggested that ticks blood-feeding on deer could be significantly controlled at all concentrations evaluated. Upcoming research will more explicitly evaluate fipronil efficacy against adult ticks and investigate potential residues in various deer tissues. Study results provide an early indication of the potential effectiveness of oral fipronil against ticks feeding on multiple host species. Field trials are needed to optimize the application scheme for delivery of oral acaricides to rodents and deer to maximize the suppression of infected ticks posing risk to humans.