A RETROSPECTIVE SUMMARY OF CERVID MORBIDITY AND MORTALITY IN ONTARIO AND NUNAVUT REGIONS OF CANADA (1991–2017) Open Access

Wild cervids, such as white-tailed deer (Odocoileus virginianus), elk (Cervus canadensis), moose (Alces alces), and caribou (Rangifer tarandus caribou), play important cultural, ecologic, and socioeconomic roles across much of the planet. As big game, they contribute to local and regional economies as well as indigenous communities by serving as food and clothing sources, and are an important component of diverse and dynamic ecosystems (Rooney and Waller 2003; Myers et al. 2004; Schuster et al. 2011). Continuous landscape and climatic changes, often attributable to anthropomorphic activities, may affect wildlife population health and effect behavioral changes. Thus, for sustainable management strategies, it is important to better understand population threats, including potential impacts of human activity. However, collecting and synthesizing such data is challenging, since these animals live and move across widespread and often remote areas, and it can be difficult and costly to recover carcasses for examination and sampling (Stallknecht 2007; Yott et al. 2011; Nicholson et al. 2016).

Long-term diagnostic datasets for free-ranging wildlife can be challenging to analyze, in part due to inconsistencies and biases surrounding carcass submission, and thus are rare within the scientific literature (Pewsner et al. 2017; Akdesir et al. 2018). However, regional datasets of morbidity and mortality in free-ranging wildlife have provided a diversity of data with applications to evolving wildlife management and conservation schemes (Pewsner et al. 2017; Akdesir et al. 2018). Available long-term, inclusive data on morbidity and mortality causes in free-ranging cervids (white-tailed deer, moose, elk, and caribou) are especially rare for the province of Ontario and the territory of Nunavut, Canada (McIntosh et al. 2007; Rosatte et al. 2007; Popp et al. 2018). White-tailed deer are primarily concentrated in the southern portion of the province with some range expansion north, while moose tend to occur in the middle to northern portions with a small southern population (Murray et al. 2012; Kennedy-Slaney et al. 2018). Elk currently comprise a small populationss, as they recently were reintroduced in Ontario, and caribou are found in small numbers in the northern portion of Ontario but mainly occur across the northern portions of Canada, including Nunavut (Rosatte 2016; Kennedy-Slaney et al. 2018).

We addressed knowledge gaps regarding causes of morbidity and mortality in free-ranging cervids in Ontario and Nunavut, Canada. Our objectives were to 1) retrospectively evaluate 27 yr of diagnostic data to identify causes of mortality and morbidity in free-ranging cervids submitted to the Canadian Wildlife Health Cooperative (CWHC), Ontario and Nunavut node; 2) assess demographic and seasonal patterns associated with select causes of mortality and morbidity among these cervids; and 3) identify potential health risks and discuss management strategies to potentially alleviate these risks. The overarching goal is to contribute to future research directions and management strategies for free-ranging wild cervid populations in Ontario and Nunavut, Canada.

Free-ranging cervids native to Canada (i.e., moose, elk, caribou, and white-tailed deer) were received for postmortem examination by the Ontario and Nunavut node of the CWHC from January 1991 to December 2017. Cases consisted of whole carcasses or select tissues collected at field necropsy and were submitted by various sources, including wildlife rehabilitation centers, veterinary clinics, private citizens, and government agencies. Data provided for each case included the date the sick animal or carcass was found, clinical history (if any), and collection location (i.e., latitude and longitude). Animals were found dead, euthanized due to morbidity (usually by gunshot), or hunter-harvested. Carcasses from rehabilitation centers and veterinary clinics were included if the animal died or was euthanized within 2 d of admission (i.e., death was attributable to natural causes not related to captivity). Dates of death were categorized by season: spring (21 March–20 June), summer (21 June–20 September), fall (21 September–20 December), and winter (21 December–20 March). Species, sex, and age (i.e., fetus, immature <1 yr, and adult ≥1 yr; based on tooth eruption and dental wear) were recorded for most cases. Gross and histologic examinations were performed for carcasses or tissues deemed adequate for diagnostic evaluation. Ancillary tests were selected as needed to arrive at a diagnosis and sometimes for surveillance purposes. Ancillary tests included histochemical stains, bacterial and fungal culture, virus isolation, enzyme-linked immunosorbent assay, PCR, serum neutralization assay, immunohistochemistry, and toxicology (e.g., gas chromatography/mass spectrometry). In addition, starting in 1999, cervids that appeared emaciated and had perceived neurologic signs underwent testing for the prion that causes chronic wasting disease (CWD) by enzyme-linked immunosorbent assay. The provided history, gross pathology, histopathology, and ancillary test results collectively were used to determine primary and any secondary (i.e., contributing) causes of morbidity or mortality.

Tissue processing for histopathology and ancillary tests were performed using standard protocols developed at the Animal Health Laboratory, an American Association of Veterinary Laboratory Diagnosticians–accredited laboratory at the University of Guelph. Parasites were evaluated microscopically and taxonomically identified to the extent possible based on morphology. Confirmatory testing for select reportable and immediately notifiable pathogens was performed at the National Centre for Foreign Animal Disease, Canadian Science Centre for Human and Animal Health, Canadian Food Inspection Agency Winnipeg laboratory. This included testing for Brucella spp. by bacterial culture of available tissues and epizootic hemorrhagic disease (EHD) virus by reverse transcription–PCR and Sanger sequencing (Pasick et al. 2001). Nematode larvae identified microscopically in brain sections of moose and elk were presumed to be Parelaphostrongylus spp. based on host, anatomic location, and known occurrence in the geographic region. Moose and elk with microscopic lesions consistent with Parelaphostrongylus spp. infection (e.g., linear rarefied tracts, hemorrhage, and associated inflammation and hemosiderin pigment consistent with damage from migration tracts) but no nematodes were considered suspect positive and listed as Parelaphostrongylus sp. in summaries of diagnoses and subsequent statistical analyses.

The primary causes of morbidity and mortality were broadly differentiated as noninfectious, infectious, or unknown. Noninfectious causes consisted of trauma, toxicosis, metabolic disorders, emaciation, neoplasia, or unknown. Trauma was further subcategorized as collision (e.g., fence, vehicular, train), illegal shooting (i.e., excluding euthanasia due to morbidity or legal hunter-harvest), predation, intraspecific aggression, and unknown cause. Noninfectious diagnoses often involved ruling out other potential causes of mortality (e.g., infectious disease) and were collectively determined in consideration of the history and gross and microscopic findings. Neoplasia was diagnosed based on cell morphology of the predominant neoplastic cell population(s) and in two cases, immunohistochemistry (cytokeratin and vimentin) was performed. Infectious causes were subcategorized by etiology as bacterial, viral, parasitic, fungal, and suspect infectious. The latter were based on gross and microscopic lesion patterns (i.e., inflammatory cell types and distribution) consistent with these general etiologies but without visualization or laboratory confirmation of the etiologic agent.

Statistical analyses were performed using STA-TA (Intercooled Stata/IC, version 14.0, StataCorp LP, College Station, Texas, USA). Univariable logistic regression was used to examine the association between select common causes of mortality (i.e., all infectious and noninfectious causes and emaciation) and the following variables: age, sex, and season. Due to small sample size (n=6), fetuses were excluded from statistical analyses. Exact logistic regression was used if low effective sample sizes posed estimation issues, and the scoring method was used to calculate P-values for these models (Dohoo et al. 2009). A significance level of α=0.05 was used for all analyses.

A total of 580 cases submitted to the CWHC were included in the study. Four cervid species were represented, the majority of which were white-tailed deer, followed by moose, elk, and caribou (Table 1). Males and females were equally represented; most were adults and the majority of cases were submitted in fall and spring (Table 1). Between one and 67 cases were received annually, with an average of 21.5 cases per year throughout the study period. Twelve cases were received in 1991 and fewer than six were received annually from 1993 to 1997. The highest numbers of case submissions were received in 2009 (n=44), 2010 (n=67), and 2011 (n=66). The majority of samples were obtained in southern Ontario (Fig. 1). Location data were not provided for 24 cases.

Noninfectious disease was the most common general cause of morbidity and mortality diagnosed among all cervid cases submitted (Table 2). Trauma was the most commonly diagnosed subcategory of noninfectious disease, as well as the most commonly identified cause of mortality overall (Table 2). The most common type of trauma detected was due to vehicular collisions, followed by illegal shooting. Predation and intraspecific fighting were less commonly identified types of trauma (Table 3). Sixty-nine of these trauma cases (n=110) were adults (62.7%; 95% confidence interval [CI]: 53.0–71.7), 35 were immature animals (31.8%; 95% CI: 23.3–41.4), and six were animals of an unknown age (5.5%; 95% CI: 2.0–11.5). Based on univariable logistic regression, there was no significant association between the odds of being diagnosed with a trauma-related death and age class (Supplementary Material Table 1). Elk were most commonly diagnosed with trauma-related death, followed by white-tailed deer; trauma was most often attributed to vehicular collision in both species (elk: n=22; white-tailed deer: n=17; Table 3). Of the elk diagnosed with trauma, most were hit by cars and trucks (12/22; 55%; 95% CI: 32.2–75.6), followed by trains (8/22; 36%; 95% CI: 17.2–59.3), and the majority of incidents occurred in the winter season (9/22; 41%; 95% CI: 20.7–63.6).

Emaciation was the second most common cause of morbidity and mortality within the category of noninfectious disease (Table 2). The odds of being diagnosed with emaciation were significantly reduced in males compared to females (Supplementary Table 1). Based on exact logistic regression, emaciation diagnoses were significantly associated with season (Supplementary Table 1). The odds of being diagnosed with emaciation were significantly greater in immature animals compared to adults (Supplementary Table 1).

Other less frequently diagnosed noninfectious causes of morbidity or mortality included neoplasia, toxicosis, and metabolic disorders (Table 2). Of the 18 neoplasia cases, 12 were diagnosed in white-tailed deer. The most commonly diagnosed neoplasm in white-tailed deer was cutaneous fibroma (9/12; 75%; 95% CI: 42.8–94.5) and single cases of an unclassified nasal tumor, oligodendroglioma, and intramuscular (scapular) polyps (Table 2). Moose were the only other species diagnosed with neoplasia (6/18; 33%; 95% CI: 13.3–59.0), which included cutaneous fibroma (3/6; 50%; 95% CI: 11.8–88.2) and single cases of unclassified sarcoma (in diaphragm and ribs), lymphoma (intra-abdominal), and suspected rhabdomyosarcoma (Table 2). Tumor diagnosis was often challenged by postmortem autolysis.

Morbidity and mortality in cervids were also attributed to infectious disease (Table 2). Adult males accounted for the majority of these, and most cases were submitted in the fall (Table 1). Based on univariable logistic regression, immature animals had significantly lower odds of mortality attributed to an infectious cause compared to adults (Supplementary Table 1). Season was significantly associated with the odds of a diagnosis of infectious causes of mortality (Supplementary Table 1).

Bacterial causes were the second most common cause of mortality overall among all cervids and were also the most commonly diagnosed subcategory of infectious disease in all species except moose (Table 2). Within the bacterial subcategory for white-tailed deer, intracranial abscesses comprised the majority of infections (15/40; 38%; 95% CI: 22.7–54.1), with Trueperella pyogenes cultured from eight of these (8/15; 53%; 95% CI: 26.6–78.7). Multiple bacterial species were cultured from the remainder of these abscesses, including Fusobacterium necrophorum and one case of Streptococcus sp. (no bacteria were cultured from one case). The majority of intracranial abscesses was diagnosed in males (13/15; 87%; 95% CI: 59.5–-98.3) versus females (2/15; 13%; 95% CI: 1.7–40.4) and adults (11/15; 73%; 95% CI: 44.9–92.2) followed by immature animals (3/15; 20%; 95% CI: 4.3–48.1) and those of unknown age (1/15; 7%; 95% CI: 0.2–31.9). These cases occurred primarily in the fall (8/15; 53%; 95% CI: 26.6–78.7), followed by winter (5/15; 33%; 95% CI: 11.8–61.6), spring (1/15; 7%; 95% CI: 0.2–31.9), and summer (1/15; 7%; 95% CI: 0.2–31.9). Three abscesses were in the pituitary gland.

Bacterial infections were deemed the primary cause of morbidity or mortality in the majority of caribou (Table 2).The majority of caribou diagnosed with bacterial infections were of unknown age (13/25; 52%; 95% CI: 31.3–72.2), followed by adults (9/25; 36%; 95% CI: 18.0–57.5) and immature animals (2/ 25; 16%; 95% CI: 4.5–36.0) and one fetus (4%; 95% CI: 0.1–20.3). Digital limb infections (i.e., foot rot) comprised the majority of bacterial infections in caribou (8/25; 32%; 95% CI: 14.9–53.5). Multiple bacterial species were cultured from all foot rot cases. The most frequently isolated bacteria were T. pyogenes (6/8; 75%; 95% CI: 34.9–96.8), and Staphylococcus aureus (6/8; 75%; 95% CI: 34.9–96.8). Fusobacterium necrophorum, Escherichia coli, Corynebacterium ulcerans, Streptococcus dysgalactiae, Enterococcus faecalis, and Pseudomonas sp. were less frequently isolated, with one case each (1/8; 13%; 95% CI: 0.3–52.7). Mixed anaerobic infections were also detected, although the bacterial species was not identified (6/8; 75%; 95% CI: 34.9–96.8). Additionally, there were seven cases of brucellosis in caribou (Brucella suis biovar 4; 28%; 95% CI: 12.0–49.4).

Within the parasitic subcategory, moose were the most commonly diagnosed cervid (Table 2). For moose, specific parasitic etiologies included P. tenuis (43/67; 64%; 95% CI: 51.5–75.5), Taenia krabbei (including the larval forms, Cysticercus tarandi; 12/67; 18%; 95% CI: 9.6–29.2), Echinococcus granulosus (5/67; 8%; 95% CI: 2.5–16.6), Dermacentor albipictus (4/67; 6%; 95% CI: 1.7–15.0), idiopathic eosinophilic myositis (2/67; 3%; 95% CI: 0.3–10.3), and Dictyocaulus viviparus (1/67; 1%; 95% CI: 0.0–8.0). All cases of parasitism in elk in this study (Table 2) were attributed to P. tenuis migration in the brain (10/10; 100%; 95% CI: 69.1–100.0).

Confirmed viral causes of morbidity and mortality were rare and included two white-tailed deer that died of EHD virus-2. None of 173 cervids tested for CWD from 1999 to 2017 had evidence of the prion that causes CWD (97.5% CI: 0.0–2.1).

Trauma was the most common cause of morbidity and mortality among all cervids in Ontario and Nunavut in this 27-yr study. Collisions with motorized vehicles were frequently diagnosed, consistent with retrospective studies in other wildlife taxa, including ungulates (Pewsner et al. 2017; Akdesir et al. 2018; Navas-Suárez et al. 2018). In Ontario, over 18,000 wildlife-vehicle collisions are reported annually, and in Canada, moose and deer are involved in the majority of these collisions (Pynn and Pynn 2004; Bramati et al. 2012). In the present study, elk appeared to be the most disaster-prone of all cervid species with traumatic fatalities, including collisions with stationary (e.g., fences) and moving objects (e.g., motor vehicles and trains). Elk hit by trains were detected more frequently during the winter season, consistent with a recent study in Ontario that demonstrated that elk seek railroad corridors as alternatives to areas with greater snow depth (Popp et al. 2018).

Bacterial infections were the second most common cause of morbidity and mortality among cervids in the present study. Intracranial abscesses were diagnosed in numerous white-tailed deer, with T. pyogenes being the most common etiology. The majority of intracranial abscesses were in adult bucks in the fall, consistent with observations in Georgia and Maryland, US (Baumann et al. 2001; Karns et al. 2009; Cohen et al. 2015). Trueperella pyogenes is a commensal bacterium on the skin and mucosal membranes of apparently healthy deer and cattle, and tends to lead to abscess formation after it gains access to internal organs, including the brain (Moore et al. 2010; Cohen et al. 2018). It is most likely transmitted from deer to deer during breeding-associated activities, such as sparring among bucks, marking by rubbing on vegetation, and antler casting, all of which typically occur during the fall rut in North America (Karns et al. 2009). In three deer, intracranial abscess primarily involved the pituitary gland, which has been rarely documented in free-ranging white-tailed deer (Al Dissi et al. 2011; Elsmo and Fenton 2019).

Caribou populations are in decline across North America, fueling the need to identify and understand potential threats to their survival (Racey 2005; Festa-Bianchet et al. 2011; Schwantje et al. 2014). While pathogens may not serve as a primary cause of population reduction, they may decrease resiliency within a herd through weakened immunity and negative energy balance (Racey 2005; Festa-Bianchet et al. 2011; Schwantje et al. 2014). We identified bacteria, mainly T. pyogenes and S. aureus (associated with digital limb infections or foot rot) and B. suis biovar 4, as the primary causes of morbidity and mortality in caribou. Digital limb infections in livestock are typically caused by F. necrophorum, a fastidious anaerobic bacterium that has been identified worldwide in wild and farmed ruminants (Leighton 2001; Handeland et al. 2010). Trueperella pyogenes and S. aureus are not commonly implicated in digital limb infections in caribou; however, findings in this study were similar to those of Handeland et al. (2010) in which T. pyogenes and S. aureus were commonly isolated in Norwegian wild tundra reindeer (Rangifer tarandus tarandus). These findings differ from those of wild North American elk (Cervus elaphus) in Washington, US, where treponemes have been isolated and identified as the cause of debilitating hoof lesions (Clegg et al. 2015).

In addition to being a recognized zoonosis, B. suis serovar 4 is recognized as an important pathogen in wild caribou and reindeer, including those in Canada, where it is enzootic (Schwantje et al. 2014). It can cause lameness associated with chronic bursitis and arthritis and reproductive disorders (e.g., abortion, placenta retention, metritis, epididymitis, orchitis, neonatal morbidity and mortality, and sterility). These effects can have a long-term impact on caribou reproduction and thus herd longevity (Tessaro and Forbes 1986; Ferguson 1997; Rhyan 2013; Schwantje et al. 2014). Brucella suis serovar 4–associated disease in caribou in the present study typically manifested as bursitis and orchitis.

Moose populations along the southern edge of their North American range have been in decline, especially in Minnesota, Manitoba, northeastern Ontario, Nova Scotia, New Hampshire, Maine, and Vermont, and parasitism has been identified as a potential contributing factor (Lankester 2010; Timmermann and Rodgers 2017; Jones et al. 2018). Of primary concern is a parasitic metastrongylid, P. tenuis, that can cause severe morbidity and mortality in aberrant host species (e.g., moose and elk; Weiss et al. 2008; Purdy et al. 2012; Mittelman et al. 2017). Clinical disease occurs due to penetration of migrating larvae into the central nervous system, potentially leading to ataxia, circling, head tilt, hind-end paresis, and death (Lankester 2010; Dobey et al. 2014). White-tailed deer serve as the natural host of this parasite, and infections in aberrant hosts tend to be more prevalent in the presence of high-density white-tailed deer populations (Whitlaw and Lankester 1994; Lankester 2010; Jones et al. 2018). In the present study, the majority of parasitic cases in moose were due to P. tenuis, which is not surprising due to the historical presence of this parasite in Ontario (Whitlaw and Lankester 1994; Lankester 2010). Similar to another Ontario study (McIntosh et al. 2007), in our study, elk also appeared to suffer from parasitic infections, particularly P. tenuis. Currently, elk populations in Ontario reflect reintroduction efforts (Rosatte et al. 2007; Yott et al. 2011), and in some areas, the lack of long-term success of reintroduction has been attributed to P. tenuis, which is suspected to play a similar role in other cases of elk reintroduction across the eastern US (Bender et al. 2005; McIntosh et al. 2007; Chitwood et al. 2018). Continued surveillance efforts are needed to understand the evolving ecology of P. tenuis infections in moose and elk, as climate and land use changes may augment this likely threat if territory overlap increases between moose, elk, white-tailed deer, and the parasite's intermediate invertebrate hosts (Whitlaw and Lankester 1994).

There is an apparent resurgence of winter tick disease (caused by D. albipictus) and associated population declines among moose in North America, especially among immature animals (i.e., 10–11 mo old; Musante et al. 2010; Bergeron et al. 2013; Jones et al. 2018). This increase in detected cases is thought to be associated with climate and land use changes, as environmental conditions have become more favorable to ticks in some locations (Lankester 2010; Wake et al. 2014; Jones et al. 2018). While elk and white-tailed deer also serve as primary hosts of D. albipictus, moose tend to experience higher tick burdens and greater clinical impacts, including hair loss, anemia, and anorexia (Musante et al. 2010; Jones et al. 2018). While D. albipictus has been shown to cause significant disease in other studies, it was rarely diagnosed as a cause of morbidity and mortality in Ontario moose. This warrants further investigation, as it was difficult to extrapolate the significance of this finding due to small sample size and opportunistic data collection.

Neoplasia and viruses were less commonly identified as causes of morbidity and mortality in cervids in Ontario, similar to other studies of free-ranging wildlife (Pewsner et al. 2017; Akdesir et al. 2018; Smith et al. 2018). Cutaneous fibroma, often associated with papilloma virus infection, was the most commonly diagnosed tumor among cervids in the present study, consistent with previous observations (Sundberg and Nielsen 1981; Sundberg et al. 1985). Fibromas were diagnosed in white-tailed deer and moose. Disseminated lymphoma was diagnosed in a moose. Lymphoma has been previously reported in a variety of cervid species, including moose (Kistner and Hayes 1971; Pewsner et al. 2017). Diagnoses of viral infections were limited to EHD virus in two white-tailed deer; this virus had not previously been reported in Ontario (Allen et al. 2019). The potential for an EHD or bluetongue virus epizootic among cervids in Ontario is unknown but would seemingly be facilitated by climate change (Ruder et al. 2015).

We did not detect the prion that causes CWD among cervids in Ontario, consistent with ongoing provincial surveillance efforts among free-ranging white-tailed deer (MNRF 2019a). As CWD was not the primary focus of diagnostic evaluations during the study period, these results should be interpreted with caution, as they do not represent consistent efforts to survey or characterize this disease or its prevalence in the study region. This disease, caused by an abnormally folded protein (i.e., prion), leads to fatal degenerative disease in all native North American cervid species (Joly et al. 2003; Miller and Walter 2019). Chronic wasting disease was diagnosed in eight mule deer (Odocoileus hemionus hemionus) and black-tailed deer (Odocoileus hemionus columbianus) imported to the Toronto Zoo from the US in the late 1970s. These deer were isolated within the captive herd, and the last of these animals died in 1981 (Williams and Young 1992; Dubé et al. 2006). Ontario maintains a state of vigilance, as it shares borders with CWD-positive states of Minnesota, Wisconsin, Michigan, and New York (Joly et al. 2003; Michigan Department of Natural Resources 2019; MNRF 2019b). In addition, in the fall of 2018, CWD was identified in a herd of farmed red deer (Cervus elaphus) in neighboring Quebec (Canadian Food Inspection Agency 2019; Michigan Department of Natural Resources 2019). Thus, ongoing and future CWD surveillance in Ontario focusing on early prion detection, as well as decreasing the risk of entry of live cervids to the province, is crucial (MNRF 2019b).

We attempted to identify potential health risks to Ontario and Nunavut wild cervid populations through retrospective review of a long-term diagnostic dataset. Anthropogenic, infectious, and environmental factors were commonly identified as causes of morbidity and mortality. Trauma was commonly diagnosed and thus for future mitigation and management, migration pathways, breeding grounds, and feeding areas of free-ranging cervids should be identified and considered to reduce negative population-level impacts of landscape development (Forman and Alexander 1998; Trombulak and Frissell 2000). Additionally, climate change may facilitate the expansion and transmission of some parasites and pathogens (e.g., those that are vector borne), potentially negatively impacting wild cervids in Ontario, Nunavut, and other northern latitudes (Allen et al. 2019; Caminade et al. 2019). Thus far, the prion that causes CWD has not been detected in Ontario cervids; nevertheless, resources should be mobilized toward minimizing risk of entry and allowing for early detection and for effective responses to minimize spread if detected. Finally, education and clear communication of scientific findings to the public and policy makers will increase awareness of cervid conservation and help guide informed management decisions.

Multi-year, retrospective analyses of diagnostic data in wildlife can provide valuable insights; however, these datasets also carry inherent limitations and biases (Stallknecht 2007; Sieber et al. 2010). Proximity to human populations, weather, geography, available personnel, financial constraints, and public attitude all affect detection and submission of wildlife cases. Thus, findings may not accurately represent the status of wild cervid populations across Ontario and Nunavut. Further, examination of selected tissues (vs. whole carcasses) limited the ability to diagnose some conditions, yet exclusion of field-collected tissues would have further biased against animals in remote northern areas such as Nunavut, and against species for which size limits the feasibility of sending whole carcasses (i.e., moose). Despite these limitations, passive diagnostic and surveillance data can help identify nonhunting mortality factors and provide suggestions of potential stressors, as well as identify circulating pathogens in wildlife populations and thus, may signal potential population-level threats. Northern latitudes, including Canada, are especially sensitive to the effects of climate change, further fueling the need to gather retrospective and prospective diagnostic and health data on cervids and other wildlife species that may benefit from targeted management actions or broader conservation efforts.

We thank all those who submitted carcasses, Canadian Wildlife Health Cooperative personnel (David Cristo, Laura Doughtery, Dan Hugues, Lenny Shirose) and Shannon French for logistic support. We are indebted to Doug Campbell, who conducted the majority of the necropsies and provided valuable insights (“disaster-prone”). S.E.A. was supported by scholarships from the OMAFRA–University of Guelph Research Program (2015-2212), the Natural Sciences and Engineering Research Council of Canada, the Ontario Federation of Anglers and Hunters, and the Ontario Veterinary College.

Supplementary material for this article is online at http://dx.doi.org/10.7589/JWD-D-19-00018.