Anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) is an emerging concern in grazing livestock, including the North American bison (Bison bison). Nevertheless, little is known about routine parasite control practices in ranched bison herds. This cross-sectional survey of bison producers in 22 states across the southern and central United States characterized herd demographics, pasture management, nutrition, animal sourcing, and anthelmintic use. Seventy-nine producers from 15 states responded, most managing herds on fewer than 300 acres. Parasite control was predominantly drug-centric: 87.3% (69/79) dewormed at least once annually, 31.6% (25/79) treated in both warm and cool seasons, and nearly one-third dewormed more than twice per year. Macrocyclic lactones (ivermectin: 65.7%, moxidectin: 29.9%) and benzimidazoles (fenbendazole: 50.8%, albendazole: 28.4%) were widely used, frequently in rotation or combination; 28.1% (18/64) administered multiple dewormers simultaneously. Only 34.8% (23/66) dosed based on individual body weights, while most relied on visual estimates or herd averages, and fewer than 10% (7/70) intentionally left animals untreated as refugia. Although 64% (46/72) and 65% (47/72) reported moderate-to-high concern (≥3/5), about internal nematodes and AR, respectively, routine diagnostics (fecal egg counts, fecal egg count reduction tests, targeted selective treatment) were rarely employed. These findings reveal that intensive whole-herd deworming, minimal diagnostics, and limited refugia are common within the US bison industry, likely increasing selection pressure for AR and underscoring the need for bison-specific, evidence-based, diagnostic-driven parasite control guidelines and education.

Pathogens can shape their host communities over various timescales. The potential role of host–pathogen co-evolution in driving contemporary shifts in disease ecology is becoming increasingly important as host species emerge and persist outside their native ranges. In North America, Mycoplasma ovipneumoniae can cause fatal pneumonia epizootics in native bighorn sheep (Ovis canadensis), whereas introduced free-ranging sympatric aoudad (Ammotragus lervia) typically act as asymptomatic reservoirs. We describe the responses of two hosts with different biogeographical histories to shared pathogen exposure through a lens of potential host–pathogen co-evolution. Specifically, this work integrates findings on microbiome composition and host transcriptomic responses in aoudad and bighorn sheep before and after controlled exposure to M. ovipneumoniae, with or without leukotoxigenic Pasteurellaceae. Aoudad maintained significantly higher microbial richness (Shannon) in the lower respiratory tract, whereas bighorn sheep experienced post-exposure microbiome perturbations and enhanced growth of some opportunistic taxa. Both molecular detection of and humoral antibodies to M. ovipneumoniae reduced the relative abundance of key genera (e.g., Bibersteinia, Mannheimia, Pasteurella, Roseomonas) in the upper respiratory tract, but post-exposure bacterial community alteration was more pronounced in bighorn sheep. Transcriptome profiling revealed that, compared to aoudad, bighorn sheep upregulated pro-inflammatory and oxidative-stress pathways—including interleukin-1, interleukin-12, and NF-κB signaling—alongside reactive oxygen species generation. In contrast, aoudad exhibited comparatively muted inflammatory signatures, enhanced expression of molecular chaperones, antigen-processing machinery, and integrin-mediated regulatory genes (notably CD46, ILK, and NFKBIZ). Network analysis identified distinct hub genes likely underpinning effective pathogen clearance and mucosal resilience in aoudad versus immunopathology in bighorn sheep. Our integrated microbiome and transcriptomic data underscore the importance of co-evolutionary history in driving host-specific responses to shared respiratory pathogens. Aoudad display microbiome stability and balanced immunoregulation, whereas bighorn sheep suffer dysbiosis and excessive inflammation, potentially increasing mortality risk. Explicit consideration of evolutionary and ecological context regarding host–pathogen co-evolution may increase overall understanding of observed pathobiological and epidemiological patterns commonly targeted for disease management interventions.

This study evaluates the role of aoudad (Ammotragus lervia) as a maintenance host and reservoir for significant respiratory pathogens hindering bighorn sheep (Ovis canadensis) conservation; Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae. An experimental commingling trial and regional disease surveillance revealed significant interspecies transmission risks and epidemiological patterns. Experimentally, 80% of bighorn sheep exposed to aoudad inoculated with M. ovipneumoniae and leukotoxigenic Pasteurellaceae died of pneumonia under both indirect and direct contact conditions. Conversely, aoudad exhibited prolonged relatively asymptomatic shedding of M. ovipneumoniae without severe clinical outcomes. Surveillance of 351 free-ranging aoudad revealed 9.4% with M. ovipneumoniae DNA in nasal swabs and M. ovipneumoniae-specific antibodies in 55.8%. Aoudad diagnostic profiles were heterogeneous across populations, including variations in strain diversity and distribution. Shedding rates were higher among juveniles than adults. Aoudad can sustain and transmit M. ovipneumoniae under free-ranging and experimental conditions, presenting significant risks to bighorn sheep populations. Research on strategies to mitigate pathogen transmission, such as reducing shared water access and aoudad removal, is critical for predicting complex biological outcomes for multi-species management. This study emphasizes the importance of longitudinal herd-specific disease surveillance and fundamental pathobiology research for understanding M. ovipneumoniae dynamics in aoudad to inform bighorn sheep conservation efforts in Texas.

White-tailed deer (Odocoileus virginianus) have high value for research, conservation, agriculture, and recreation and might be key SARS-CoV-2 reservoirs. In November 2023, we sampled 15 female deer in a captive facility in Texas, USA. All deer had neutralizing antibodies to SARS-CoV-2; respiratory swab samples from 11 deer were SARS-CoV-2-positive by quantitative reverse transcription PCR, and 1 deer also had a positive rectal swab sample. Six of the 11 respiratory swab samples yielded infectious virus; replication kinetics of most samples displayed lower growth 24-48 hours postinfection in vitro than Omicron lineages isolated from humans in Texas in the same period. Virus growth was similar between groups by 72 hours, suggesting no strong attenuation of deer-derived virus. All deer viruses clustered in XBB Omicron clade and demonstrated more mutations than expected compared with contemporaneous viruses in humans, suggesting that crossing the species barrier was accompanied by a high substitution rate.

Gastrointestinal nematodes (GIN) live in complex communities within American plains bison (Bison bison), a keystone ungulate species of North American prairie ecosystems. These trichostrongylid nematode species vary in their level of pathogenicity and can cause disease ranging from subclinical to clinical. However, the GIN species diversity and distribution of North American bison are understudied, especially in conservation herds in the United States. Fecal samples from conservation bison were collected from six herds in 2022, with five of those herds resampled in 2023 across six states (Colorado, Iowa, Nebraska, North Dakota, South Dakota, Oklahoma). Fecal samples from a herd of longhorn cattle that co-graze with a bison herd from Oklahoma were also collected in both years. Following fecal egg counts and coproculture, third-stage larvae were processed using ITS2 rDNA metabarcoding to determine the trichostrongylid species composition and screened for the 200Y (TTC > TAC) polymorphisms of the isotype-1 β-tubulin gene to assess possible benzimidazole resistance. Alpha diversity was determined for each herd using the Shannon and the inverse Simpson diversity Index. The Beta diversity was assessed between herds using the Bray-Curtis dissimilarity index. The three most common species found were Haemonchus placei, Ostertagia ostertagi, and Cooperia oncophora. The herds with the highest parasite species diversity were in Oklahoma, Iowa, and North Dakota. The herd in Colorado showed the least diverse parasite communities. Over the course of the two-year study, moderate to high GIN species diversity was observed across several of the conservation bison herds. Additionally, different parasite species proportions were determined between co-grazing bison and cattle herds. Lastly, low frequencies of the 200Y (TTC > TAC) polymorphisms, associated with benzimidazole resistance, were detected. Our study reveals differences in species diversity and richness among conservation bison herds across the United States and provides the first evidence of benzimidazole resistance markers in wild bison in North America.

Improved methods are needed to prevent wildlife deaths from anthrax. Caused by Bacillus anthracis, naturally occurring outbreaks of anthrax are frequent but unpredictable. The commercially available veterinary vaccine is labeled for subcutaneous injection and is impractical for large-scale wildlife vaccination programs; therefore, oral vaccination is the most realistic method to control and prevent these outbreaks. We reported the induction of an anthrax-specific lethal toxin (LeTx) neutralizing antibody response in mice following oral vaccination with alginate microcapsules containing B. anthracis Sterne strain 34F2 spores, coated with poly-L-lysine (PLL) and vitelline protein B (VpB). We continued evaluating our novel vaccine formulation through this proof-of-concept study in white-tailed deer (WTD; Odocoileus virginianus; n = 9). We orally vaccinatedWTD via needle-free syringe with three formulations of the encapsulated vaccine: 1) PLL-VpB-coated microcapsules with 10(7-8) spores/ml (n = 5), 2) PLL-VpB-coated microcapsules with 10(9-10) spores/ml (n = 2), and 3) PLL-coated microcapsules with 10(9-10) spores/ml (n = 2). Although the limited sample sizes require continued experimentation, we observed an anthrax-specific antibody response in WTD serum following oral vaccination with PLL-coated microcapsules containing 10(9) spores/ml. Furthermore, this antibody response neutralized anthrax LeTx in vitro, suggesting that continued development of this vaccine may allow for realistic wildlife anthrax vaccination programs.

Outbreaks of anthrax, caused by the soilborne bacterium Bacillus anthracis, are a continuous threat to free-ranging livestock and wildlife in enzootic regions of the United States, sometimes causing mass mortalities. Injectable anthrax vaccines are commercially available for use in livestock, and although hand injection is not a cost- or time-effective long-term management plan for prevention in wildlife, it may provide a tool for managers to target selectively animals of high conservation or economic value. Vaccine-induced anthrax-specific antibody responses have been reported previously in white-tailed deer (Odocoileus virginianus), but the protective nature was not determined. In this study, five white-tailed deer were subcutaneously vaccinated with one dose (1 mL) of the Anthrax Spore Vaccine. Eight blood collections by jugular venipuncture were conducted over 146 d to measure the anthrax-specific antibody response in each deer's serum over time. Antibodies were first detected by ELISA and later with toxin neutralization assays to estimate in vitro protection. Average peak absorbance by ELISA occurred at 14 d postvaccination, whereas average peak in vitro protection occurred at 28 d postvaccination. Observed in vitro protection on average for white-tailed deer after this single-dose vaccination protocol lasted 42-56 d postvaccination, although three individuals still maintained lethal toxin-neutralizing serum antibody titers out to 112 d postvaccination. Vaccination responses were variable but effective to some degree in all white-tailed deer.

Feral populations of aoudad (Ammotragus lervia) occur in Texas bighorn sheep (Ovis canadensis) habitat and pose several conceptual ecological threats to bighorn sheep re-establishment efforts. The potential threat of disease transmission from aoudad to bighorn sheep may exacerbate these issues, but the host competency of aoudad and subsequent pathophysiology and transmissibility of pneumonic pathogens involved in the bighorn sheep respiratory disease complex is largely unknown. Because the largest population-limiting diseases of bighorn sheep involve pathogens causing bronchopneumonia, we evaluated the host competency of aoudad for Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae. Specifically, we described the shedding dynamics, pathogen carriage, seroconversion, clinical patterns, and pathological effects of experimental infection among wild aoudad held in captivity. We found that aoudad are competent hosts capable of maintaining and intraspecifically transmitting Mycoplasma ovipneumoniae and Pasteurellaceae and can shed the bacteria for 53 days after exposure. Aoudad developed limited clinical signs and pathological findings ranged from mild chronic lymphohistiocytic bronchointerstitial pneumonia to severe and acute suppurative pneumonia, similarly, observed in bighorn sheep infected with Mycoplasma spp. and Pasteurellaceae bacteria, respectively. Furthermore, as expected, clinical signs and lesions were often more severe in aoudad inoculated with a combination of Mycoplasma ovipneumoniae and Pasteurellaceae as compared to aoudad inoculated with only Mycoplasma ovipneumoniae. There may be evidence of interindividual susceptibility, pathogenicity, and/or transmissibility, indicated by individual aoudad maintaining varying severities of chronic infection who may be carriers continuously shedding pathogens. This is the first study to date to demonstrate that aoudad are a conceptual disease transmission threat to sympatric bighorn sheep populations due to their host competency and intraspecific transmission capabilities.

We unsuccessfully attempted to safely chemically immobilize a roan antelope (Hippotragus equinus) with a premixed combination of medetomidine (5 mg/mL) and ketamine (150 mg/mL) for injury treatment. This dose (0.066 mg/kg medetomidine and 1.96 mg/kg ketamine) produced poor quality of immobilization, probably exacerbated by stimulation before completing induction.

Free-ranging white-tailed deer ( Odocoileus virginanus ) across the United States are increasingly recognized as involved in SARS-CoV-2 transmission cycles. Through a cross-sectional study of 80 deer at three captive cervid facilities in central and southern Texas, we provide evidence of 34 of 36 (94.4%) white-tailed deer at a single captive cervid facility seropositive for SARS-CoV-2 by neutralization assay (PRNT90), with endpoint titers as high as 1280. In contrast, all tested white-tailed deer and axis deer ( Axis axis ) at two other captive cervid facilities were seronegative, and SARS-CoV-2 RNA was not detected in respiratory swabs from deer at any of the three facilities. These data support transmission among captive deer that cannot be explained by human contact for each infected animal, as only a subset of the seropositive does had direct human contact. The facility seroprevalence was more than double of that reported from wild deer, suggesting that the confined environment may facilitate transmission. Further exploration of captive cervids and other managed animals for their role in the epizootiology of SARS-CoV-2 is critical for understanding impacts on animal health and the potential for spillback transmission to humans or other animal taxa. Importance As SARS-CoV-2 vaccine coverge of the human population increases and variants of concern continue to emerge, identification of the epidemiologic importance of animal virus reservoirs is critical. We found that nearly all (94.4%) of the captive white-tailed deer at a cervid facility in central Texas had neutralizing antibodies for SARS-CoV-2. This seroprevalence is over double than that which has been reported from free-ranging deer from other regions of the US. Horizontal transmission among deer may be facilitated in confinement. Tracking new infections among wild and confined deer is critical for understanding the importance of animal reservoirs for both veterinary and human health.

After identifying a captive herd of white-tailed deer in central Texas with >94% seroprevalence with SARS-CoV-2 neutralizing antibodies in September 2021, we worked retrospectively through archived serum samples of 21 deer and detected seroconversion of all animals between December 2020 and January 2021. We then collected prospective samples to conclude that the duration of persistence of neutralizing antibodies is at least 13 months for 19 (90.5%) of the animals, with two animals converting to seronegative after six and eight months. Antibody titres generally waned over this time frame, but three deer had a temporary 4- to 8-fold increases in plaque reduction neutralization test titres over a month after seroconversion; anamnestic response cannot be ruled out.

We evaluated the safety and efficacy of nalbuphine (40 mg/mL), plus medetomidine (10 mg/mL), plus azaperone (10 mg/mL) under the premixed label NalMed-A. From January to March 2020, 10 aoudad (Ammotragus lervia) were immobilized via dart-gun for seven separate sampling periods for a total of 45 recorded individual immobilization events. Induction and reversal times with NalMed-A were 5.53 +/- 2.61 min and (following atipamezole administration) 5.08 +/- 2.43 min while previous studies with alpha-2 agonist-ketamine combinations gave median and average induction times of 4.6 min and 11.2 min using medetomidine-ketamine and xylazine-ketamine, respectively. Overall, NalMed-A adequately immobilized aoudad, with 13% incidence of hyperthermia and 2.22% mortality when delivered via dart.

An oral vaccine against anthrax (Bacillus anthracis) is urgently needed to prevent annual anthrax outbreaks that are causing catastrophic losses in free-ranging livestock and wildlife worldwide. The Sterne vaccine, the current injectable livestock vaccine, is a suspension of live attenuated B. anthracis Sterne strain 34F2 spores (Sterne spores) in saponin. It is not effective when administered orally and individual subcutaneous injections are not a practical method of vaccination for wildlife. In this study, we report the development of a microencapsulated oral vaccine against anthrax. Evaluating Sterne spore stability at varying pH's in vitro revealed that spore exposure to pH 2 results in spore death, confirming that protection from the gastric environment is of main concern when producing an oral vaccine. Therefore, Sterne spores were encapsulated in alginate and coated with a protein shell containing poly-L-lysine (PLL) and vitelline protein B (VpB), a non-immunogenic, proteolysis resistant protein isolated from Fasciola hepatica. Capsule exposure to pH 2 demonstrated enhanced acid gel character suggesting that alginate microcapsules provided the necessary protection for spores to survive the gastric environment. Post vaccination IgG levels in BALBc/J mouse serum samples indicated that encapsulated spores induced anti-anthrax specific responses in both the subcutaneous and the oral vaccination groups. Furthermore, the antibody responses from both vaccination routes were protective against anthrax lethal toxin in vitro, suggesting that further optimization of this vaccine formulation may result in a reliable oral vaccine that will conveniently and effectively prevent anthrax in wildlife populations.

Hyperthermia is a common, serious issue when capturing wildlife and has the potential to cause irreversible damage and death if severe, especially among cervids. During a disease surveillance program in white-tailed deer, 72 animals were chemically immobilized for sample collection. Most of the deer became hyperthermic (body temperatures >2°C above physiological norm) and of those, three became severely hyperthermic (>4.2+°C above physiological norm). Since the deer were sedated for regulatory purposes, reversal of the immobilant was not an option to restore natural thermoregulation. Rather, flunixin meglumine was administered to each animal in conjunction with cold water enemas and/or copious external application of water. Body temperatures rapidly cooled and stabilized within normal physiological ranges after the treatment. Once the samples were collected, each deer was returned to their pens and given the immobilizing agents’ antidotes. All deer survived and appeared healthy 30 days post-capture indicating the protocol used for hyperthermia treatment was effective.

Anthrax (Bacillus anthracis) is a zoonotic disease endemic to environments worldwide. Spores, the dormant form of the bacteria, can survive for decades in nature's harshest environments and maintain their viability to cause disease. Outbreaks are common in free-ranging livestock and wildlife, thus making anthrax an economically and ecologically important disease. The currently available vaccine to protect livestock is a suspension of B. anthracis Sterne Strain 34F2 spores in saponin (Sterne vaccine). However, it is only available as a subcutaneous injection which is an impractical method of prevention for wildlife. Oral vaccination is the ideal method for free-ranging wildlife, but the Sterne vaccine has never been thoroughly evaluated for oral administration. The current study evaluated the antibody titers induced in mice by subcutaneous or oral vaccination with three different doses of the Sterne vaccine. Results described here show a gradual increase in antibody titers at each time point following subcutaneous vaccination with all vaccine doses. In contrast, no antibody response was detected from any dose or any time point after oral vaccination. Taken together, these results suggest that the Sterne vaccine is only effective as a subcutaneous injection and that an alternate oral anthrax vaccine formulation must be developed to allow for efficient vaccination of free-ranging livestock and wildlife.

Epizootic hemorrhagic disease virus is an orbivirus transmitted by Culicoides spp. In North America, it is recognized as a major cause of disease affecting white-tailed deer, but it can impact other wildlife species as well as domestic cattle. Although minimal clinical disease had been noted in Texas, periodic outbreaks in other states caused Texas cattle producers to question the risks to their cattle. The objective of this study was to estimate the proportion of Texas cattle exposed to epizootic hemorrhagic disease virus serotype 2 by observing seroprevalence in auction markets. Serum samples collected from cattle >18 mo of age sold through 11 Texas auction markets were collected during June of 2014. Antibody levels were measured using the virus neutralization test as the diagnostic protocol. Market sampling indicated 97.08% of adult cattle had been exposed to epizootic hemorrhagic disease virus serotype 2. There were no significant differences in mean titers between individual markets. However, when markets were grouped there was a significant mean titer difference between groups, increasing in the southern and western regions. The lack of clinical disease is likely related to enzootic stability as a result of high viral infections in cattle and white-tailed deer and the abundance of Culicoides vectors.

ABSTRACTChronic wasting disease (CWD) is an infectious and fatal transmissible spongiform encephalopathy of members of the family Cervidae. Although CWD has been a serious concern among wildlife managers in several states in the United States and 2 Canadian provinces for over a decade, it is not known how CWD affects movement of hosts during the preclinical and clinical phases of disease. We hypothesized that normal movement patterns are altered by CWD. We evaluated migratory status, migration corridors, dispersal behavior, hourly activity patterns, home range areas, and resource selection for white‐tailed deer (Odocoileus virginianus) of known CWD status as a means of understanding how CWD infection influenced habitat use and disease spread. We captured deer, tested for CWD by tonsil biopsy, marked deer with radio‐transmitters (2003–2010) or global positioning system collars (2006–2010), and recaptured individuals annually for CWD testing. The proportion of CWD‐positive females that migrated was significantly less than CWD‐positive males. All deer that were CWD‐negative were more active than their CWD‐positive cohabitants, which was most pronounced in fall for males when CWD‐positive deer were significantly less active throughout the day. Home range areas were small ( = 1.99 km2) and were larger for CWD‐negative females than CWD‐positive females. Resource selection analyses indicated that all deer, regardless of CWD status, sex, or migratory status selected riparian habitats. Riparian habitats represent high CWD risk areas that should be targeted for potential disease management actions (e.g., surveillance, culling, environmental treatments). © 2017 The Wildlife Society.

Chronic wasting disease (CWD) is an invariably fatal transmissible spongiform encephalopathy of white-tailed deer, mule deer, elk, and moose. Despite a 100% fatality rate, areas of high prevalence, and increasingly expanding geographic endemic areas, little is known about the population-level effects of CWD in deer. To investigate these effects, we tested the null hypothesis that high prevalence CWD did not negatively impact white-tailed deer population sustainability. The specific objectives of the study were to monitor CWD-positive and CWD-negative white-tailed deer in a high-prevalence CWD area longitudinally via radio-telemetry and global positioning system (GPS) collars. For the two populations, we determined the following: a) demographic and disease indices, b) annual survival, and c) finite rate of population growth (λ). The CWD prevalence was higher in females (42%) than males (28.8%) and hunter harvest and clinical CWD were the most frequent causes of mortality, with CWD-positive deer over-represented in harvest and total mortalities. Survival was significantly lower for CWD-positive deer and separately by sex; CWD-positive deer were 4.5 times more likely to die annually than CWD-negative deer while bucks were 1.7 times more likely to die than does. Population λ was 0.896 (0.859-0.980), which indicated a 10.4% annual decline. We show that a chronic disease that becomes endemic in wildlife populations has the potential to be population-limiting and the strong population-level effects of CWD suggest affected populations are not sustainable at high disease prevalence under current harvest levels.