Aerosol Transmission of Chronic Wasting Disease in White-Tailed Deer

While the facile transmission of chronic wasting disease (CWD) remains incompletely elucidated, studies in rodents suggest that exposure of the respiratory mucosa may be an efficient pathway. The present study was designed to address this question in the native cervid host. Here, we demonstrate aerosol transmission of CWD to deer with a prion dose >20-fold lower than that used in previous oral inoculations. Inhalation of prions may facilitate transmission of CWD and, perhaps, other prion infections.     

Prion Infectivity in Fat of Deer with Chronic Wasting Disease

Chronic wasting disease (CWD) is a neurodegenerative prion disease of cervids. Some animal prion diseases, such as bovine spongiform encephalopathy, can infect humans; however, human susceptibility to CWD is unknown. In ruminants, prion infectivity is found in central nervous system and lymphoid tissues, with smaller amounts in intestine and muscle. In mice, prion infectivity was recently detected in fat. Since ruminant fat is consumed by humans and fed to animals, we determined infectivity titers in fat from two CWD-infected deer. Deer fat devoid of muscle contained low levels of CWD infectivity and might be a risk factor for prion infection of other species.Prion diseases are fatal neurodegenerative diseases that include Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep, and chronic wasting disease (CWD) in cervids. Cross-species prion infection can occur and is responsible for the spread of BSE to humans (2). Since spread is likely due to exposure to infected tissues, it is vital to know which tissues contain infectivity. In animals such as cattle, sheep, and cervids, whose tissues are part of both the human and domestic-animal food chains, the central nervous system (CNS) has the highest propensity for infectivity. Lymphoid organs and muscles can also be positive for the disease agent, but this varies among species (1, 4, 7). We recently found prion infectivity in brown and white fat of scrapie agent-infected mice (13) and wanted to determine if fat from animals actually consumed by humans may also carry infectivity. To answer this question, we inoculated fat from two CWD agent-infected deer into susceptible transgenic mice expressing deer prion protein (TgDeerPrP mouse) (10).     

White-Tailed Deer Movements in a Chronic Wasting Disease Area in South-Central Wisconsin

Abstract: To focus white-tailed deer (Odocoileus virginianus) management within a chronic wasting disease-infected area in south-central Wisconsin, USA, we assessed deer movements and related dispersal to variation in landscape pattern, deer density, and harvest intensity. We radiocollared and monitored 165 deer between 2003 and 2005. Yearling males that dispersed (45%) had greater forest edge (i.e., fragmentation) within natal home ranges. Exploratory movements were rare for adult females. Transient and migratory movements were rare among all deer (<5%). Although yearling males have low chronic wasting disease prevalence rates, they may be infected before dispersal due to variable incubation times. Managers should increase yearling male harvest and consider removing young males in areas of higher forest edge.     

Prion-Seeding Activity in Cerebrospinal Fluid of Deer with Chronic Wasting Disease

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a uniformly fatal family of neurodegenerative diseases in mammals that includes chronic wasting disease (CWD) of cervids. The early and ante-mortem identification of TSE-infected individuals using conventional western blotting or immunohistochemistry (IHC) has proven difficult, as the levels of infectious prions in readily obtainable samples, including blood and bodily fluids, are typically beyond the limits of detection. The development of amplification-based seeding assays has been instrumental in the detection of low levels of infectious prions in clinical samples. In the present study, we evaluated the cerebrospinal fluid (CSF) of CWD-exposed (n=44) and naïve (n=4) deer (n=48 total) for CWD prions (PrP^d) using two amplification assays: serial protein misfolding cyclic amplification with polytetrafluoroethylene beads (sPMCAb) and real-time quaking induced conversion (RT-QuIC) employing a truncated Syrian hamster recombinant protein substrate. Samples were evaluated blindly in parallel with appropriate positive and negative controls. Results from amplification assays were compared to one another and to obex immunohistochemistry, and were correlated to available clinical histories including CWD inoculum source (e.g. saliva, blood), genotype, survival period, and duration of clinical signs. We found that both sPMCAb and RT-QuIC were capable of amplifying CWD prions from cervid CSF, and results correlated well with one another. Prion seeding activity in either assay was observed in approximately 50% of deer with PrP^d detected by IHC in the obex region of the brain. Important predictors of amplification included duration of clinical signs and time of first tonsil biopsy positive results, and ultimately the levels of PrP^d identified in the obex by IHC. Based on our findings, we expect that both sPMCAb and RT-QuIC may prove to be useful detection assays for the detection of prions in CSF.     

Long-Distance Movement of a White-Tailed Deer Away From a Chronic Wasting Disease Area

Abstract: Chronic wasting disease is a fatal, transmissible spongiform encephalopathy found among cervids. Spread of the disease across the landscape is believed to result from movements (dispersal, exploratory, transient, or migratory) of infected deer, serving as the vectors for the disease. We document an unusual long-distance movement of a young female, out of the chronic wasting disease eradication zone in south-central Wisconsin. This type of movement could function as a rapid, long-distance dispersing mechanism for the disease only if the following conditions are met: the deer is infected and shedding prions, the deer directly contacts other deer and transmits secretions carrying an infectious dose of prions, or an infectious dose of prions is transmitted to the environment and taken up by other deer. Despite lower prevalence rates of chronic wasting disease among young deer, we believe managers should not dismiss deer making long-distance movements such as we report, as they could serve as potential long-distance vectors of the disease.     

Deer Carcass Decomposition and Potential Scavenger Exposure to Chronic Wasting Disease

ABSTRACT Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy afflicting the Cervidae family in North America, causing neurodegeneration and ultimately death. Although there are no reports of natural cross-species transmission of CWD to noncervids, infected deer carcasses pose a potential risk of CWD exposure for other animals. We placed 40 disease-free white-tailed deer (Odocoileus virginianus) carcasses and 10 gut piles in the CWD-affected area of Wisconsin (USA) from September to April in 2003 through 2005. We used photos from remotely operated cameras to characterize scavenger visitation and relative activity. To evaluate factors driving the rate of carcass removal (decomposition), we used Kaplan-Meier survival analysis and a generalized linear mixed model. We recorded 14 species of scavenging mammals (6 visiting species) and 14 species of scavenging birds (8 visiting species). Prominent scavengers included American crows (Corvus brachyrhynchos), raccoons (Procyon lotor), and Virginia opossums (Didelphis virginiana). We found no evidence that deer consumed conspecific remains, although they visited gut piles more often than carcasses relative to temporal availability in the environment. Domestic dogs, cats, and cows either scavenged or visited carcass sites, which could lead to human exposure to CWD. Deer carcasses persisted for 18 days to 101 days depending on the season and year, whereas gut piles lasted for 3 days. Habitat did not influence carcass decomposition, but mammalian and avian scavenger activity and higher temperatures were positively associated with faster removal. Infected deer carcasses or gut piles can serve as potential sources of CWD prions to a variety of scavengers. In areas where surveillance for CWD exposure is practical, management agencies should consider strategies for testing primary scavengers of deer carcass material.     

White-tailed Deer Management Strategies and Domestication Processes

Today, people in the U.S. commonly engage in mutual relationships with white-tailed deer (WTD) in manners consistent with those that ultimately resulted in the domestication of animals in the past. Using a wide range of media depicting perspectives of sport hunters, biologists, ecologists, and game managers this paper explores: 1) the influence of anthropogenic environments on WTD behavior, 2) ‘game’ management and the ability to create valued demographics, and 3) the selection for increased antler size in farmed WTD. This study demonstrates that in order to gain a more accurate understanding of domestication, analyses should focus on the evolution of mutualisms between people and animals. Insights gleamed from this analysis also contribute toward our archaeological understanding of prehistoric animal domestication.     

Infectious Prions in Pre-Clinical Deer and Transmission of Chronic Wasting Disease Solely by Environmental Exposure

Key to understanding the epidemiology and pathogenesis of prion diseases, including chronic wasting disease (CWD) of cervids, is determining the mode of transmission from one individual to another. We have previously reported that saliva and blood from CWD-infected deer contain sufficient infectious prions to transmit disease upon passage into naïve deer. Here we again use bioassays in deer to show that blood and saliva of pre-symptomatic deer contain infectious prions capable of infecting naïve deer and that naïve deer exposed only to environmental fomites from the suites of CWD-infected deer acquired CWD infection after a period of 15 months post initial exposure. These results help to further explain the basis for the facile transmission of CWD, highlight the complexities associated with CWD transmission among cervids in their natural environment, emphasize the potential utility of blood-based testing to detect pre-clinical CWD infection, and could augur similar transmission dynamics in other prion infections.     

Chronic Wasting Disease: Transmission Mechanisms and the Possibility of Harvest Management

We develop a model of CWD management by nonselective deer harvest, currently the most feasible approach available for managing CWD in wild populations. We use the model to explore the effects of 6 common harvest strategies on disease prevalence and to identify potential optimal harvest policies for reducing disease prevalence without population collapse. The model includes 4 deer categories (juveniles, adult females, younger adult males, older adult males) that may be harvested at different rates, a food-based carrying capacity, which influences juvenile survival but not adult reproduction or survival, and seasonal force of infection terms for each deer category under differing frequency-dependent transmission dynamics resulting from environmental and direct contact mechanisms. Numerical experiments show that the interval of transmission coefficients β where the disease can be controlled is generally narrow and efficiency of a harvest policy to reduce disease prevalence depends crucially on the details of the disease transmission mechanism, in particular on the intensity of disease transmission to juveniles and the potential differences in the behavior of older and younger males that influence contact rates. Optimal harvest policy to minimize disease prevalence for each of the assumed transmission mechanisms is shown to depend on harvest intensity. Across mechanisms, a harvest that focuses on antlered deer, without distinguishing between age classes reduces disease prevalence most consistently, whereas distinguishing between young and older antlered deer produces higher uncertainty in the harvest effects on disease prevalence. Our results show that, despite uncertainties, a modelling approach can determine classes of harvest strategy that are most likely to be effective in combatting CWD.     

Cell-Based Quantification of Chronic Wasting Disease Prions

Cell-based measurement of prion infectivity is currently restricted to experimental strains of mouse-adapted scrapie. Having isolated cell cultures with susceptibility to prions from diseased elk, we describe a modification of the scrapie cell assay allowing evaluation of prions causing chronic wasting disease, a naturally occurring transmissible spongiform encephalopathy. We compare this cervid prion cell assay to bioassays in transgenic mice, the only other existing method for quantification, and show this assay to be a relatively economical and expedient alternative that will likely facilitate studies of this important prion disease.Prions consist largely or entirely of PrP^Sc, a β-sheet-rich conformer of the prion protein (PrP). During disease, PrP^Sc coerces the normal PrP^C protein to adopt the PrP^Sc conformation. While protease-sensitive forms of PrP^Sc exist (20), PrP^Sc is usually partially resistant to limited proteinase K (PK) digestion (4). Bioassays in susceptible animals have, until recently, been the sole means of assessing prion infectivity. The scrapie cell assay (SCA) (12), which relies on detection of protease resistant PrP^Sc, while a substantial advance, has been limited to the detection of mouse-adapted scrapie prions, and the development of analogous systems for naturally occurring prions is a high priority. Chronic wasting disease (CWD), a burgeoning epidemic of deer, elk, and moose, is of particular importance.We first generated a cell line susceptible to infection by cervid prions. While rabbit kidney epithelial RK13 cells expressing sheep, mouse, and bank vole PrP supported prion replication from the corresponding species (8, 14, 22), expression of human PrP did not confer susceptibility to human prions (14). We produced RK13 cells expressing elk PrP (RKE cells) and infected them with CWD brain homogenates (5). To analyze cervid PrP^Sc (CerPrP^Sc) by Western blotting, detergent extracts containing equal amounts protein were treated with 40 mg/ml PK for 1 h at 50°C and centrifuged for 1 h at 100,000 × g. Alternately, CerPrP^Sc in cells was analyzed by cell blotting (5). Infection of RKE cells with CWD resulted in detectable CerPrP^Sc 3 passages after infection; however, the progressive reduction of CerPrP^Sc upon repeated passage (Fig. ​(Fig.11 A) showed that infection was not sustained.Open in a separate windowFIG. 1.Characterization of cell cultures for studying CWD prions. (A) Western blots showing accumulation of CerPrP^Sc in RKE cells challenged with CWD brain homogenates from elk isolate 012-09442, passaged in Tg5037 mice (RKE-CWD) (left) and Elk21⁺ cells (right). Passage numbers (p) of cell cultures are indicated. (B) Expression of CerPrP^C and HIV-Gag and accumulation of CerPrP^Sc in RKE and RKE-Gag cells infected with CWD brain homogenates. Cultured cells were also analyzed by cell blotting (right). (C) Bioassay of Elk21⁺ cells propagating elk CWD 012-09442 prions (filled circles), elk CWD 012-09442 prions in Tg5037 mice (filled squares), uninfected RKE-Gag (open circles), Elk21⁻ 13 passages after DS-500 treatment (open triangles), Elk21⁻ 30 passages after DS-500 treatment (filled triangles), the Elk21-3 clone (open diamonds), and the Elk21-9 clone (open squares). (D) Western blots of CerPrP^C (100 and 50 μg total protein loaded in each case) and CerPrP^Sc (200, 100, and 50 μg total protein loaded in each case) produced in Elk21⁺ cells and Tg5037 mice inoculated with Elk21⁺ cell extracts. (E to H) CerPrP^Sc deposition in the hippocampus (E and G) and thalamus (F and H) of Tg5037 mice inoculated with either Elk21⁺ (E and F) or uninfected RKE-Gag (G and H) cell extracts. (I) Western blots demonstrating susceptibility of Elk21-3, Elk21-9, and Elk21⁻ to reinfection with elk CWD 012-09442 prions. For each cell line, the first two lanes show extracts from mock (phosphate-buffered saline [PBS])-infected cells, while the second two lanes show extracts from cells exposed to CWD brain homogenates. In all Western blots, samples were either PK treated (+) or untreated (−), and the positions of protein molecular mass markers at 37, 25, and 20 kDa (from top to bottom) are shown.Since previous reports demonstrated that retroviral Gag mediated enhanced release of mouse-adapted scrapie from cell cultures (15), RKE cells were further transfected with pcDNA3-gag expressing the HIV-1 GAG precursor protein (9), generating RKE-Gag cells. CerPrP^Sc levels in infected RKE-Gag were enhanced ∼2-fold (Fig. ​(Fig.1B).1B). Clones of infected RKE-Gag and RKE cells were derived by limited dilution. Of 40 clones isolated in each case, single RKE and RKE-Gag clones produced CerPrP^Sc. While CerPrP^Sc was not detected beyond passage 4 of cloned RKE cells (data not shown), Fig. ​Fig.1A1A shows that CerPrP^Sc production in the infected RKE-Gag clone, referred to as Elk21⁺, was sustained for 67 passages in culture, which equates to ∼223 cell doublings.Other approaches for producing cells chronically infected with CWD brain homogenates, including infection of N2a cells stably expressing elk PrP, were unsuccessful (Fig. ​(Fig.2),2), either because N2a cells are resistant to CWD brain homogenates or because CerPrP^C-to-CerPrP^Sc conversion is inhibited by expression of endogenous mouse PrP^C (21).Open in a separate windowFIG. 2.Lack of susceptibility of N2a cells expressing elk PrP to CWD. (A) Western blot showing elk and deer PrP^C expression in N2a cells. (B) Elk PrP^c-expressing N2a cells (N2a-ElkPrP) infected with CWD isolates remain uninfected after four passages. Pairs of lanes show extracts of N2a-ElkPrP cells challenged with brain homogenates from diseased Tg(CerPrP-E226)5037^+/− mice infected with elk isolates 012-022012, 012-09442, 99W12389, and 7178-47 (from left to right). Results are also shown for Elk21⁺ cells and CWD-infected Tg(CerPrP-E226)5037^+/− mice. Blots were probed with MAb 9E9, which recognizes only cervid PrP. Samples were either PK treated (+) or untreated (−), and the positions of protein molecular mass markers at 37, 25, and 20 kDa (from top to bottom) are shown.After 25 passages, Elk21⁺ cells were bioassayed in Tg(CerPrP-E226)5037^+/− mice expressing elk PrP (3), referred to as Tg5037 mice. Mice developed prion disease with a mean incubation time of 112 ± 1 days. Tg5037 mice inoculated with the same prions as those used to produce Elk21⁺ cells developed disease with a mean incubation time of 126 ± 2 days, while Tg5037 mice challenged with RKE-Gag cells remained asymptomatic (Fig. ​(Fig.1C).1C). Mice were inoculated with infected brain and cell culture preparations containing similar amounts of PrP^Sc as quantified by Western blot analysis. For bioassays of uninfected cells, mice were inoculated with preparations containing amounts of total protein equivalent to those in infected cell cultures.Levels of CerPrP^C and CerPrP^Sc and their electrophoretic migration and glycosylation patterns differed between Elk21⁺ cells and Tg5037 mice (Fig. ​(Fig.1D1D and ​and2).2). CerPrP^Sc deposition in the brains of Tg5037 mice infected with Elk21⁺ cells was diffuse and granular (Fig. 1E and F), in accordance with previous reports (3); no disease occurred in Tg5037 mice inoculated with RKE-Gag cells (Fig. 1G and H).Elk21⁺ cells were treated with the antiprion compound dextran sulfate 500 (DS-500) (7, 11, 13). CerPrP^Sc was undetectable after 5 weeks and did not reemerge when cells were returned to medium lacking drug (Fig. ​(Fig.1I).1I). Tg5037 mice remained asymptomatic for >355 days following inoculation (Fig. ​(Fig.1C).1C). Cells cured of PrP^Sc by DS-500, referred to as Elk21⁻ cells, retained the ability to sustain production of CerPrP^Sc when rechallenged with elk CWD brain homogenates (Fig. ​(Fig.1I).1I). The process of cloning of Elk21⁺ cells after 58 passages in culture also resulted in elimination of PrP^Sc in a subset of subclones. While Western and cell blotting detected CerPrP^Sc in 3 subclones, 11 subclones did not produce CerPrP^Sc. Of the 11 “negative” subclones rechallenged with CWD brain homogenates, 10 produced CerPrP^Sc (for example, clone Elk21-3 [Fig. ​[Fig.1I]),1I]), while clone Elk21-9 was resistant to CWD (Fig. ​(Fig.1I).1I). The CWD-free statuses of clones Elk21-3 and Elk21-9 were confirmed in Tg5037 mice (Fig. ​(Fig.1C1C).We adapted the SCA (12, 16, 17) to visualize infected Elk21⁻ or Elk21-3 cells. We refer to this as the cervid prion cell assay (CPCA) (see the supplemental material). Briefly, susceptible Elk21⁻ cells in 96-well plates were exposed to serial dilutions of CWD brain homogenates ranging from 10⁻² to 10⁻⁵ in a volume of 100 μl. Cell cultures were split once at 1:4 and twice at 1:7, which effectively diluted out CerPrP^Sc in the inoculum. Inclusion of RK13 cells stably transfected with empty vector (RKV cells) showed that positive spots detected after three splits were the result of newly generated CerPrP^Sc. After the final passage, 20,000 cells were filtered onto Multiscreen IP 96-well, 0.45-μm filter plates (enzyme-linked immunospot [ELISPOT] assay plates; Millipore, Billerica, MA) or AcroWell 96-well, 0.45-μm BioTrace filter plates (Pall, East Hills, NY). Cells were subjected to PK digestion and denaturation with guanidinium thiocyanate. CerPrP^Sc-producing cells were detected by an enzyme-linked immunosorbent assay (ELISA) using anti-PrP monoclonal antibody (MAb) 6H4, followed by alkaline phosphatase (AP)-conjugated secondary anti-mouse IgG, and developed with NBT/BCIP. Images were scanned with CTL ELISPOT equipment, and spot numbers were determined using ImmunoSpot3 software (Cellular Technology, Ltd., Shaker Heights, OH). Figure ​Figure33 A depicts magnifications of ELISPOT filters of infected Elk21⁻ cells.Open in a separate windowFIG. 3.Quantification of elk CWD prion infectivity by the transgenic mouse bioassay and the cervid prion cell assay. (A) Representative wells of an ELISPOT plate showing spots given by duplicate Elk21⁺ cells exposed to 3-fold serial dilutions of pooled elk CWD brain homogenates, between 10⁻³ and 10^−4.4. (B) Double-logarithmic plot of spot number versus brain homogenate dilution showing the linear response of the CPCA. Elk21⁻ cells infected with dilutions of pooled elk CWD brain homogenates (open circles) and pooled elk CWD brain homogenates passaged in Tg5037 mice (filled circles). In each case, the mean is derived from 6 independent experiments performed in triplicate, with error bars indicating the standard errors of the means (SEM). (C) Responsiveness of Elk21⁻ and Elk21-3 cells to various CWD brain homogenates. The cells were infected with serial 1:3 dilutions of homogenates of CWD-infected brains and subjected to the CPCA. In each case, the dilution required to yield 300 positive cells per 20,000 cells after the third split was calculated. Solid black line, CPCA of CWD brain homogenates from diseased elk brain, using Elk21⁻ cells; solid gray lines, CPCA of CWD brain homogenates from diseased Tg5037 mice, using Elk21⁻ cells; dashed gray line, CPCA using Elk21-3 cells. Filled triangles, D10 CWD isolate; open circles, pooled elk CWD brain homogenate; filled circles, brain homogenate of Tg5037 mice infected with pooled elk CWD; filled diamonds, 012-09442 CWD isolate; filled squares, 01-0306 CWD isolate.To determine the dose-response relationship of Elk21⁻ cells to CWD brain homogenates, we used a pooled elk CWD inoculum titrated in two different transgenic mouse lines (3, 6). In the case of Tg5037 mice, we estimated the titer to be 10^7.0 intracerebral (i.c.) 50% infective doses (ID₅₀)/g of brain, and the titer in Tg(CerPrP)1536^+/− mice expressing deer PrP was estimated at 10^7.2 i.c. ID₅₀/g (Table ​(Table1)1) (19).

TABLE 1.

CWD infectivity assays

Susceptibility of Domestic Cats to Chronic Wasting Disease

Domestic and nondomestic cats have been shown to be susceptible to feline spongiform encephalopathy (FSE), almost certainly caused by consumption of bovine spongiform encephalopathy (BSE)-contaminated meat. Because domestic and free-ranging nondomestic felids scavenge cervid carcasses, including those in areas affected by chronic wasting disease (CWD), we evaluated the susceptibility of the domestic cat (Felis catus) to CWD infection experimentally. Cohorts of 5 cats each were inoculated intracerebrally (i.c.) or orally (p.o.) with CWD-infected deer brain. At 40 and 42 months postinoculation, two i.c.-inoculated cats developed signs consistent with prion disease, including a stilted gait, weight loss, anorexia, polydipsia, patterned motor behaviors, head and tail tremors, and ataxia, and the cats progressed to terminal disease within 5 months. Brains from these two cats were pooled and inoculated into cohorts of cats by the i.c., p.o., and intraperitoneal and subcutaneous (i.p./s.c.) routes. Upon subpassage, feline CWD was transmitted to all i.c.-inoculated cats with a decreased incubation period of 23 to 27 months. Feline-adapted CWD (Fel^CWD) was demonstrated in the brains of all of the affected cats by Western blotting and immunohistochemical analysis. Magnetic resonance imaging revealed abnormalities in clinically ill cats, which included multifocal T2 fluid attenuated inversion recovery (FLAIR) signal hyperintensities, ventricular size increases, prominent sulci, and white matter tract cavitation. Currently, 3 of 4 i.p./s.c.- and 2 of 4 p.o. secondary passage-inoculated cats have developed abnormal behavior patterns consistent with the early stage of feline CWD. These results demonstrate that CWD can be transmitted and adapted to the domestic cat, thus raising the issue of potential cervid-to-feline transmission in nature.     

Hunter and Nonhunter Beliefs about Chronic Wasting Disease in Wisconsin

Abstract: We examined beliefs of landowners who hunt and do not hunt regarding chronic wasting disease (CWD) and its management. We mailed surveys to a random sample of 973 Wisconsin, USA, landowners living in the CWD southwest disease eradication zone. Of 613 respondents, 360 (59%) were hunters and 253 (41%) were not hunters. We created multiple item indices to measure respondent beliefs about effects of CWD and its management. Hunters and nonhunters differed on 5 of 6 belief indices. Both groups were, on average, relatively neutral in their trust of the Wisconsin Department of Natural Resources but landowners who did not hunt reported slightly higher trust. Both groups were neutral or slightly agreed that CWD should be managed and they were concerned about deer (Odocoileus spp.) health and the safety of eating venison. Landowners who did not hunt were more likely than those who hunted to agree with these issues but effect sizes indicated these differences were minimal. Landowners who hunted were more concerned than nonhunters about effects of CWD on deer hunting. Cluster analyses indicated most nonhunting landowners were neutral or not concerned about CWD and its management, whereas most hunting landowners were concerned. Our results suggest that managers should use communication campaigns to increase awareness and mitigate concerns about CWD, increase trust and input related to the disease, and inform publics about CWD management strategies.     

Evaluating Indirect Effects of Hunting on Mule Deer Spatial Behavior

Mule deer (Odocoileus hemionus) are widely hunted throughout western North America and are experiencing population declines across much of their range. Consequently, understanding the direct and indirect effects of hunting is important for management of mule deer populations. Managers can influence deer mortality rates through changes in hunting season length or authorized tag numbers. Little is known, however, about how hunting can affect site fidelity patterns and subsequent habitat use and movement patterns of mule deer. Understanding these patterns is especially important for adult females because changes in behavior may influence their ability to acquire resources and ultimately affect their productivity. Between 2008 and 2013, we obtained global positioning system locations for 42 adult female deer at the Starkey Experimental Forest and Range in northeast Oregon, USA, during 5-day control and treatment periods in which hunters were absent (pre-hunt), present but not actively hunting (scout and post-hunt), and actively hunting male mule deer (hunt) on the landscape. We estimated summer home ranges and 5-day use areas during pre-hunt and hunt periods and calculated overlap metrics across home ranges and use areas to assess site fidelity within and across years. We used step selection functions to evaluate whether female mule deer responded to human hunters by adjusting fine-scale habitat selection and movement patterns during the hunting season compared to the pre-hunt period. Mule deer maintained site fidelity despite disturbance by hunters with 72 ± 4% (SE) within-year overlap between summer home ranges and hunt use areas and 54 ± 7% inter-annual overlap among pre-hunt use areas and 56 ± 7% among hunt use areas. Mule deer diurnal movement rates, when hunters are active on the landscape, were higher during the hunting period versus pre-hunt or scout periods. In contrast, nocturnal movement rates, when hunters are inactive on the landscape, were similar between hunting and non-hunting periods. Additionally, during the hunt, female mule deer hourly movements increased in areas with high greenness values, indicating that mule deer spent less time in areas with more vegetative productivity. Female mule deer maintained consistent habitat selection patterns before and during hunts, selecting areas that offered more forest canopy cover and high levels of vegetative productivity. Our results indicate that deer at Starkey are adopting behavioral strategies in response to hunters by increasing their movement rates and selecting habitat in well-established ranges. Therefore, considering site fidelity behavior in management planning could provide important information about the spatial behavior of animals and potential energetic costs incurred, especially by non-target animals during hunting season. © 2020 The Wildlife Society.     

Rumen Ciliates of White-tailed Deer (Odocoileus virginianus), Axis Deer (Axis axis), Sika Deer (Cervus nippon) and Fallow Deer (Dama dama) from Texas

Samples of rumen contents from 33 white-tailed deer (Odocoileus virginianus), 31 axis deer (Axis axis), 26 sika deer (Cervus nippon), and 25 fallow deer (Dama dama) were collected from four study areas in central Texas. The geometric mean concentration of total protozoa was 50.2 x 10(4) per ml, with no differences between species (P > 0.36). White-tailed deer had a higher percentage of Entodinium and lower percentage of Diplodiniinae (P < 0.01) than the other deer species, which were not different from each other. Occurrence of Epidinium, Isotricha, and Dasytricha was sporadic and did not differ among deer species. Numerous new host records of protozoan species were observed: white-tailed deer--four; axis deer--five; sika deer--five; fallow deer--four. This brings the total number of protozoan species identified in each deer species to: white-tailed--eight; axis--12; sika--15; fallow--16. For all species combined, protozoan concentration were 7.5 to 11-fold higher (P < 0.01) from Area 4, which differed from the other three areas by having a stream that allowed deer to have free access to water. Criteria used for identification of medium-size Eudiplodinium species were evaluated.     

Early and Non-Invasive Detection of Chronic Wasting Disease Prions in Elk Feces by Real-Time Quaking Induced Conversion

Chronic wasting disease (CWD) is a fatal prion disease of wild and captive cervids in North America. Prions are infectious agents composed of a misfolded version of a host-encoded protein, termed PrP^Sc. Infected cervids excrete and secrete prions, contributing to lateral transmission. Geographical distribution is expanding and case numbers in wild cervids are increasing. Recently, the first European cases of CWD have been reported in a wild reindeer and two moose from Norway. Therefore, methods to detect the infection early in the incubation time using easily available samples are desirable to facilitate effective disease management. We have adapted the real-time quaking induced conversion (RT-QuIC) assay, a sensitive in vitro prion amplification method, for pre-clinical detection of prion seeding activity in elk feces. Testing fecal samples from orally inoculated elk taken at various time points post infection revealed early shedding and detectable prion seeding activity throughout the disease course. Early shedding was also found in two elk encoding a PrP genotype associated with reduced susceptibility for CWD. In summary, we suggest that detection of CWD prions in feces by RT-QuIC may become a useful tool to support CWD surveillance in wild and captive cervids. The finding of early shedding independent of the elk’s prion protein genotype raises the question whether prolonged survival is beneficial, considering accumulation of environmental prions and its contribution to CWD transmission upon extended duration of shedding.