Managing plague on prairie dog colonies: insecticides as ectoparasiticides

Abstract

Human health practitioners and wildlife biologists use insecticides to manage plague by suppressing fleas (Siphonaptera), but insecticides can also kill other ectoparasites. We investigated effects of deltamethrin and fipronil on ectoparasites from black‐tailed prairie dogs (Cynomys ludovicianus, BTPDs). In late July, 2018, we treated three sites with 0.05% deltamethrin dust and 5 sites with host‐fed 0.005% fipronil grain. Three non‐treated sites functioned as experimental baselines. We collected ectoparasites before treatments (June‐July, 2018) and after treatments (August‐October, 2018, June‐July, 2019). Both deltamethrin and fipronil suppressed fleas for at least 12 months. Deltamethrin had no detectable effect on mites (Arachnida). Fipronil suppressed mites for at least 12 months. Lice (Phthiraptera) were scarce on non‐treated sites throughout the study, complicating interpretation. Concentrating on eight sites where all three ectoparasites where found in June‐July, 2018 (before treatments), flea intensity was greatest on BTPDs carrying many lice and mites. These three ectoparasites co‐occurred at high numbers, which might facilitate plague transmission in some cases. Lethal effects of insecticides on ectoparasite communities are potentially advantageous in the context of plague management.

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

“…We analyzed data from planned field experiments on BTPD survival, body condition, and reproduction (during which flea control with fipronil grain was effective for ≥12 months [ 16 , 25 , 26 ]), and a new investigation of flea control with FIP grain. Trapping and sampling of BTPDs at Buffalo Gap National Grassland and Badlands National Park, South Dakota were conducted under IACUC protocol 2015–07 (U.S. Geological Survey, Fort Collins Science Center, Colorado).…”

“…Data were collected in South Dakota, USA, Buffalo Gap National Grassland (43°51’N, 102°03’W), Badlands National Park (43°47’N, 102°08’W), and Lower Brule Indian Reservation (44°03’N, 99°40’W). BTPDs were trapped, aged (adult or juvenile by size), marked with ear-tags, identified, and sampled for fleas under the methods of Eads et al [ 16 , 25 ]. At Buffalo Gap and Badlands, sampling occurred on “sites”, defined as collections of juxtaposed burrows that may be treated with FIP grain or remain non-treated as baselines.…”

“…Experiments with bait-delivered FIP and BTPDs started in early 2016 [ 12 ] and expanded later the same year [ 16 , 25 ]. In Colorado, wheat seed grain with 0.005% FIP by weight suppressed fleas on BTPDs for at least 6 weeks [ 12 ].…”

“…In Colorado, wheat seed grain with 0.005% FIP by weight suppressed fleas on BTPDs for at least 6 weeks [ 12 ]. During complementary experiments in South Dakota, FIP grain and newly-developed FIP bait pellets suppressed fleas for at least 12–14 months and up to 24 months in many cases [ 16 , 25 , 26 ]. This degree and duration of flea control might eliminate plague epizootics and protect BTPDs and other wildlife during inter-epizootic periods, as observed with deltamethrin [ 27 ], but field research is needed for confirmation.…”

“…After observing no negative effects in captivity, we conducted field experiments on flea control; flea reductions were substantial, lasting 12 months or more in nearly all cases [ 16 , 25 , 26 ]. Concurrently, we evaluated effects of FIP grain on BTPD survival.…”