Flea Control on Prairie Dogs (Cynomys Spp.) With Fipronil Bait Pellets: Potential Plague Mitigation Tool for Rapid Field Application and Wildlife Conservation

Abstract

Sylvatic plague is a widespread, primarily flea-vectored disease in western North America. Because plague is highly lethal to endangered black-footed ferrets (Mustela nigripes, BFFs) and the prairie dogs (Cynomys spp., PDs) on which BFFs depend for habitat and prey, minimizing the impacts of plague is a priority at BFF reintroduction sites. We developed a new, flour-based bait pellet containing 0.84 mg of fipronil and weighing ~1.25 g (FipBits). We measured the degree and duration of flea control on black-tailed PDs (C. ludovicianus) in Montana and on Gunnison's PDs (C. gunnisoni) in Arizona, USA from 2018-2020. FipBits were distributed on treated plots one time at a rate of 125/ha. Fleas were virtually eliminated in Montana from 1 mo posttreatment to 1 yr later and remained substantially depressed 2 yr posttreatment. With the split colony design, we probably underestimated the degree of flea control achieved with FipBits due to crossover edge effects along the arbitrary line dividing the plots. Flea control in Arizona was significant from 1 mo posttreatment to 1 yr later, but flea abundance had recovered by 2 yr posttreatment. Flea control was evaluated from 2020-2021 in South Dakota, USA on four plots treated with three concentrations of fipronil in FipBits (0.68, 0.71, and 0.83 mg/FipBit). Fleas were essentially eliminated for 10 mo on the 0.83-mg plot and were substantially reduced on the two 0.71-mg plots. Fleas were reduced on the 0.68-mg plot, but the degree of control was less than observed on other treated plots. Impacts of plague on PDs and BFFs would probably be greatly reduced by the levels of flea control observed with FipBits. Options for expanded FipBit evaluations are being pursued for what may become a highly practical, affordable, and effective plague mitigation tool.

Evaluating Baits With Lufenuron and Nitenpyram for Flea Control on Prairie Dogs (Cynomys Spp.) to Mitigate Plague

“…FipBits build upon previous bait production methods (Corro et al 2017), distribution machinery (Kreiger and Matchett 2019), and successful flea control with fipronil-treated grain (Eads et al 2019). In field studies, FipBits proved effective in controlling PD fleas for 12-24 mo in most cases (Eads et al 2021a; Matchett et al 2023), similar to the duration of flea control with fipronil grain (Eads et al 2019). Other systemic insecticides used in domestic animals might be incorporated into similar baits.…”

“…Recently, baits containing fipronil, a GABA receptor antagonist, have proven effective in controlling Xenopsylla , Oropsylla , and Pulex spp. fleas (Leirs et al 2001; Poché et al 2017; Eads et al 2019, 2021a; Matchett et al 2023). Fipronil baits have been incorporated into conservation plans for some host species and efforts are underway to refine bait formulations and application methods (Eads et al 2021a; Matchett et al 2023).…”

“…fleas (Leirs et al 2001; Poché et al 2017; Eads et al 2019, 2021a; Matchett et al 2023). Fipronil baits have been incorporated into conservation plans for some host species and efforts are underway to refine bait formulations and application methods (Eads et al 2021a; Matchett et al 2023).…”

Lethal Effects on Flea Larvae of Fipronil in Host Feces: Potential Benefits for Plague Mitigation

“…We suspect some BTPDs consume >1 FipBit under natural conditions. Thus, scat from FipBit-treated BTPDs also may kill several flea life stages, including larvae, helping to explain long-term flea control with FipBits (Eads et al 2021; Matchett et al 2023).…”

“…Prairie dogs ( Cynomys spp., PDs) are colonial sciurids highly susceptible to Y. pestis , and insecticides are commonly used to protect PDs, as well as nearby human populations, against plague, especially at reintroduction sites for black-footed ferrets ( Mustela nigripes ), which are endangered obligate predators of PDs (Matchett et al 2010; Eads and Biggins 2015, 2019). During multiyear, replicated field experiments, fipronil bait treatments suppressed adult fleas on PDs for 12–24 mo (Eads et al 2019, 2020, 2021; Matchett et al 2023). Fipronil grain bait is now being used for plague management at multiple black-footed ferret reintroduction sites.…”