Fipronil Baits as Emerging Tools for Flea Control and Plague Mitigation: Experiments with Cricetid Mice on Prairie Dog Colonies.

Plague is a zoonotic disease of mammalian hosts and flea vectors. Wildlife biologists most commonly mitigate plague by controlling flea populations. We evaluated the efficacy of edible baits for systemic flea control with two cricetid species on colonies of black-tailed prairie dogs (Cynomys ludovicianus): the western deer mouse (Peromyscus sonoriensis) and the northern grasshopper mouse (Onychomys leucogaster). We tested grain bait with 0.005% fipronil by weight and "FipBit" pellets with 0.46-1.52 mg of fipronil/pellet. Flea prevalence was assessed via combing of live-trapped mice. In one experiment with fipronil grain bait and FipBits (n=564 combings), flea prevalence declined from 74% (grain) and 45% (FipBits) before treatments to 0% for both treatments from 30-44 d and from 324-413 d after treatments. During a second experiment with FipBits (n=299 combings), flea prevalence declined from 13% to 32% before treatments to 0% from 11-15 d after treatments, but increased to 29-56% from 349-378 d after treatments. Results herein suggest annual fipronil bait treatments may be most effective for flea control.