Assembling a safe and effective toolbox for integrated flea control and plague mitigation: Fipronil experiments with prairie dogs

PLoS One. 2022 Aug 8;17(8):e0272419. doi: 10.1371/journal.pone.0272419. eCollection 2022.

Abstract

Background: Plague, a widely distributed zoonotic disease of mammalian hosts and flea vectors, poses a significant risk to ecosystems throughout much of Earth. Conservation biologists use insecticides for flea control and plague mitigation. Here, we evaluate the use of an insecticide grain bait, laced with 0.005% fipronil (FIP) by weight, with black-tailed prairie dogs (BTPDs, Cynomys ludovicianus). We consider safety measures, flea control, BTPD body condition, BTPD survival, efficacy of plague mitigation, and the speed of FIP grain application vs. infusing BTPD burrows with insecticide dusts. We also explore conservation implications for endangered black-footed ferrets (Mustela nigripes), which are specialized predators of Cynomys.

Principal findings: During 5- and 10-day laboratory trials in Colorado, USA, 2016-2017, FIP grain had no detectable acute toxic effect on 20 BTPDs that readily consumed the grain. During field experiments in South Dakota, USA, 2016-2020, FIP grain suppressed fleas on BTPDs for at least 12 months and up to 24 months in many cases; short-term flea control on a few sites was poor for unknown reasons. In an area of South Dakota where plague circulation appeared low or absent, FIP grain had no detectable effect, positive or negative, on BTPD survival. Experimental results suggest FIP grain may have improved BTPD body condition (mass:foot) and reproduction (juveniles:adults). During a 2019 plague epizootic in Colorado, BTPDs on 238 ha habitat were protected by FIP grain, whereas BTPDs were nearly eliminated on non-treated habitat. Applications of FIP grain were 2-4 times faster than dusting BTPD burrows.

Significance: Deltamethrin dust is the most commonly used insecticide for plague mitigation on Cynomys colonies. Fleas on BTPD colonies exhibit the ability to evolve resistance to deltamethrin after repeated annual treatments. Thus, more tools are needed. Accumulating data show orally-delivered FIP is safe and usually effective for flea control with BTPDs, though potential acute toxic effects cannot be ruled out. With continued study and refinement, FIP might be used in rotation with, or even replace deltamethrin, and serve an important role in Cynomys and black-footed ferret conservation. More broadly, our stepwise approach to research on FIP may function as a template or guide for evaluations of insecticides in the context of wildlife conservation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Ecosystem
  • Ferrets
  • Flea Infestations* / drug therapy
  • Flea Infestations* / prevention & control
  • Flea Infestations* / veterinary
  • Insecticides* / pharmacology
  • Nitriles
  • Plague* / prevention & control
  • Plague* / veterinary
  • Pyrazoles
  • Pyrethrins*
  • Rodent Diseases*
  • Sciuridae
  • Siphonaptera*
  • Yersinia pestis*

Substances

  • Insecticides
  • Nitriles
  • Pyrazoles
  • Pyrethrins
  • fipronil

Grants and funding

Funding and logistical support were provided by the National Park Service (DE, DB, TL) https://www.nps.gov/index.htm; US Fish and Wildlife Service (JH, DB, DE, NK, EH, DL) https://fws.gov/; US Geological Survey (DA, DE) https://www.usgs.gov/; Prairie Wildlife Research (TL) https://prairiewildlife.org; US Forest Service (PD) https://www.fs.usda.gov/; Colorado State University (DE, DB) https://www.colostate.edu/; Lower Brule Indian Reservation (SG) https://www.lowerbrulesiouxtribe.com/; World Wildlife Fund (DE, TL, DB) https://www.worldwildlife.org/; and National Fish and Wildlife Foundation (partners) https://www.nfwf.org/. Conceptualization: Listed authors/scientists associated with USGS, PWR, USFWS, USFS, NPS, Lower Brule. Data curation: Listed authors/scientists associated with USGS, Lower Brule, USFWS. Data analysis: Listed authors/scientists associated with USGS, USFWS, Lower Brule. Funding acquisition: Listed authors/scientists associated with USGS, PWR, USFWS, USFS, NPS, Lower Brule. Methodology: Listed authors/scientists associated with USGS, PWR, USFWS, USFS, NPS, Lower Brule. Project administration: Listed authors/scientists associated with USGS, PWR, USFWS, USFS, NPS, Lower Brule. Writing: Listed authors/scientists associated with USGS, PWR, USFWS, USFS, NPS, Lower Brule. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.