Analysis of supplemental wildlife feeding in Mississippi and environmental gastrointestinal parasite load.

Wildlife species are host to a variety of gastrointestinal parasites (GIPs). Artificially concentrating animals may increase the risk of disease spread due to increased GIP load and associated environmental load. Supplemental feeding of deer is common among hunters and known to concentrate animals, but there is limited knowledge of how it affects GIP environmental load. GIP load was compared between ecologically-equivalent pairs of sites in Mississippi with and without year-round supplemental feeding (average distance between pairs = 147 m). During May-August in 2019 and 2020, feces from white-tailed deer and raccoons were collected and examined for the presence of nematodes, coccidia, Giardia spp., Cryptosporidium spp., and Baylisascaris procyonis. On average, fed sites had 8 more deer (241% increase) and 2 more raccoon fecal piles (540% increase) than unfed sites. Average parasite loads for individual fecal samples did not differ between fed and unfed sites, but the greater number of deer and raccoon fecal piles at fed sites (p < 0.0001) produced 231% and 308% greater environmental loads of nematodes and coccidia, respectively. Spin feeders, the only feeder type that distributed feed on the ground, had 326% more coccidia in feces on average compared to other feeder types (p < 0.03). These results show that supplemental feeding of white-tailed deer, especially with spin feeders, increases environmental loads of GIP and the potential for transmission of parasitic diseases.

Identifying Aflatoxin Exposure Risk from Supplemental Feeding of Deer.

Aflatoxins, common contaminants of crops and feed, are a health risk to wild and domestic animals. Past research found aflatoxins in feed and feeders provided for wild herbivores valued for recreational hunting (hereafter: game) species but are consumed by various species. We determined the current extent of aflatoxin contamination in wildlife feed and white-tailed deer (Odocoileus virginianus) feeders, examined aflatoxin production in corn piles over time, and quantified nontarget wildlife visitation to deer feeders. We sampled feeders (n=107) in Mississippi, US, bagged/bulk feed sources (n=64) in the southeastern US, as well as corn piles exposed to environmental contamination over 10 d (n=20) during May-January of 2019 and 2020. We found aflatoxins (≥5 parts per billion [ppb]) in feeders during summer (4% prevalence, 58±71 ppb mean±SD) and hunting season (October-January, 6%, 60±1 ppb) and in bagged/bulk feed during hunting season (11%, 13±8 ppb). After 8 d, aflatoxins were detected in all summer corn piles at toxic levels (483-3,475 ppb), although none were detected in hunting season piles after day one. Nontarget wildlife identified at feeders included 16 mammalian and 18 avian species. Numerous wildlife species are at risk for aflatoxin exposure due to supplemental feeding of deer, with the primary risk factor in the southeastern US being summertime environmental exposure of feed to aflatoxin-producing fungi.

Managing plague on prairie dog colonies: insecticides as ectoparasiticides.

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.