A retrospective study of the diagnoses and survival of elk admitted to a large animal referral clinic

Abstract

Abstract – Information for veterinarians regarding diseases of farmed elk remains scarce despite an increase in the size of the industry. This retrospective study examines all (n = 245) elk cases admitted to the Western College of Veterinary Medicine over an 11-year period (1991 to 2001). Age, gender, date of admission, diagnosis, and outcome were examined. Diarrhea, fractures, and other musculoskeletal problems were most common. Most (76%) cases involved elk under 1 y of age; these were more commonly diagnosed with fractures or diarrheal disease. Elk older than 1 y of age tended to be diagnosed with fractures or noninfectious diseases. Overall, the most common diagnosis was fractures, which were seen mostly as traumatic catastrophic long bone fractures. Fractures and other musculoskeletal problems occurred towards the end of summer and into the fall, while diarrhea and other infectious diseases were diagnosed in young elk in the spring and summer. The in-hospital case fatality rate was 33.5%.

Introduction

Game farming and ranching is an expanding industry in North American agriculture. This trend has been well documented in western Canada over the past decade, with farmed elk (Cervus elaphus) representing a major proportion of the industry (1). Large animal veterinary clinics are experiencing higher caseloads of elk due to this growing trend. Much of the knowledge currently utilized in farming elk is extrapolated from other cervid management systems, such as captive red deer in New Zealand. Little, however, has been documented on specific diseases of captive elk or the nature of the cases presented to veterinarians (1–3). Clinicians can be reluctant to take on new species because of the lack of information available regarding the common diseases seen and their management. Knowledge of the frequency of diseases and the age or seasonal distribution of these diseases will help clinicians to make a diagnosis. The purpose of this paper is to describe the nature and distribution of diseases of the farmed elk in western Canada that were admitted on a referral or primary care basis to the Large Animal Clinic of the Western College of Veterinary Medicine (WCVM) Veterinary Teaching Hospital, University of Saskatchewan over an 11-year period. Associations between patient age, month of presentation, diagnosis, and patient discharge status are discussed.

Materials and methods

Medical records of all elk admitted to the WCVM between the years 1991 and 2001, inclusive, were reviewed. Elk with multiple admissions for different presenting complaints were included; however, elk with subsequent admissions associated with the presenting complaint (most notably rechecks and cast changes) were not included. Information collected from medical records included the gender, age, date of admission, presenting complaint, second opinion versus primary care, diagnosis, and discharge status (alive, euthanized, or died). Statements in this manuscript regarding prognosis refer to that given at the time of discharge from the clinic. Diagnoses were divided into 12 different categories according to the primary anatomic site of the lesion: 1) musculoskeletal (fracture), 2) enteric, 3) umbilical, 4) central nervous system, 5) urogenital, 6) rectal and anal, 7) pulmonary, 8) septicemia, 9) musculoskeletal (except fractures), 10) ocular, 11) integument, and 12) other. Fractures were placed into a separate category due to the high frequency of this diagnosis. Diagnosis was categorized as septicemia, if there were multiple sites of involvement and if confirmed on necropsy. Diagnoses were placed into the “other” category, if they did not fit into the named categories adequately.

Trends between diagnostic categories and age, date of admission, and discharge status were tested with a Mantel Haenszel Chi-square test. Odds ratios were calculated to assess the risk of mortality with the various specific, diagnostic categories compared with the other cateogries. Fisher’s Exact test was used to see if any statistically significant difference existed between any of the above comparisons, and if the observed risk was statistically significant. A P-value of 0.05 was used to test significance.

For purposes of comparison with a Chi-Square, age was categorized into 3 groups. These were yearling (< 1 y), juvenile (1 to 3 y), and adult (> 3 y). Month of presentation was categorized into 4 seasons (spring, summer, fall, winter).

Results

During the 11-year period, there were 245 admissions of elk with different presenting complaints. Of the 245 admissions, 50.6% were female, 47.2% were male, and 2.1% were unrecorded. The ages ranged from 1 d to 13 y, with most animals (76%) being ≤ 1 y (Figure 1). June, September, and July were the months when the highest numbers of elk were admitted (Figure 2). Table 1 shows the distribution of the different disease categories among the various seasons and age classes. Two hundred and eighty-one separate diagnoses were made for the 245 admissions (multiple admissions were made for some elk). Thirty-two percent of the cases were admitted for secondary or tertiary care, while 68% of the cases were seen on a primary care basis. This difference was not found to be significantly different (P = 0.07).

Figure 1.

Number of sick elk (y-axis) by age (x-axis) presented over an 11-year period.

Figure 2.

Number of sick elk (y-axis) by month of presentation (x-axis) over an 11-year period.

Table 1.

Seasonal and age class frequency of different diagnostic categories of diseased elk

	Seasonal frequency (%)				Age class frequency (%)
Diagnostic category	Spring	Summer	Fall	Winter	Yearling	Juvenile	Adult
Fractures	12.9	38.7	25.8	22.6	72.6	22.6	4.8
Enteric	8.9	80	8.9	2.2	88.9	4.4	6.7
Umbilical	0	15.4	69.2	15.4	84.6	0	15.4
Central nervous system	9.1	63.6	9.1	18.2	63.6	27.3	9.1
Urogenital	0	0	50	50	0	50	50
Rectal/anal	25	25	12.5	37.5	37.5	37.5	25
Pulmonary	7.1	78.6	14.3	0	100	0	0
Septicemia	11.8	76.5	0	11.8	82.3	0	17.6
Musculoskeletal	9.1	33.3	42.4	15.2	45.5	18.2	36.4
Ocular	0	14.3	85.7	0	85.7	14.3	0
Integument	37.5	25	12.5	25	50	25	25

Of the 245 elk admissions, 163 (66.5%) were discharged alive, 42 (17.2%) were euthanized, and 40 (16.3%) died of disease. In-hospital case fatality rate (euthanasia and natural death) for elk ≤ 1 y and > 1 y was 34.4% and 30.5%, respectively. Fatality was significantly higher in the 25 elk diagnosed with multiple concurrent conditions than in the 220 diagnosed with only 1 condition, 72.0% versus 29.4%, respectively (P < 0.001). Table 2 shows the frequency, proportion of second opinion cases, and the case fatality rate of the various diseases categories. The fatality rate for elk with infectious diseases was similar to that for elk with noninfectious diseases (P = 0.75). Whether the case was 1st opinion or 2nd opinion did not significantly affect fatality rate, 31.9% versus 37.2%, respectively. However, there was a significant association between disease condition and whether the case was 1st or 2nd opinion (P = 0.005).

Table 2.

Frequency, proportion referred, and case fatality rates of different types of disease in elk

	Number	Frequency (%)	Proportion referred (%)	In-hospital case fatality (%)
Musculoskeletal (fractures)	62	22.10	40.3	29
Enteric	45	16.00	22.2	40
Umbilical	13	4.60	15.4	8
Central nervous system	11	3.90	36.4	90
Urogenital	10	3.60	30.0	0
Rectal/Anal	8	2.90	50.0	12.5
Pulmonary	14	5.00	14.3	64
Septicemia	17	6.10	35.3	100
Musculoskeletal (except fractures)	33	11.80	57.8	36
Ocular	7	2.50	0.0	14
Integument	8	2.80	50.0	25
Other	53	18.90	20.8	36
Total	281	100	32.0	33.5

Nine (3.7%) cases were undiagnosed. Of these, 8 were discharged alive and 1 was euthanized; 1 presented for lameness, 2 for central nervous system diseases, 2 for chronic weight loss, and 4 for unlocalized inflammatory chronic diseases. The undiagnosed cases comprised 2 elk < 1 mo, 3 between 1 mo and 6 mo, and 4 < 2 y. There was no association between undiagnosed cases and the body system affected (P = 0.81), or the age of the patient (P = 0.72).

Overall, there were strong associations between diagnosis and patient outcome (P = 0.03), age of patient (P = 0.048), and season of presentation (P = 0.02), this means that certain diagnoses (diarrhea, fractures, pneumonia) are seen in certain age groups during certain seasons and tend to have certain outcomes, and that these observations are statistically significant. There were, however, no significant differences in the outcomes of juvenile versus yearling or adult elk (P = 0.78). There was also no significant difference in the outcomes of the elk presented in different seasons — spring, summer, fall, or winter (P = 0.91). Most infectious diseases were diagnosed in neonatal and very young elk, while most noninfectious diseases were diagnosed in older elk and were largely traumatic in origin.

Fractures were the most commonly diagnosed; long bone fractures were most frequently reported (n = 47, 76%), with 23 (37%) being comminuted. Other fractures involved the carpi and tarsi (n = 4), skull (n = 3), vertebrae (n = 2), mandible (n = 2), acetabulum (n = 2), and phalanges (n = 2). Elk diagnosed with fractures had a 29% in-hospital case fatality rate, all the result of euthanasia. There was no statistically significant risk or trend between type of fracture and survival. Most fractures (81%) were seen in elk ≥ 2 mo, no elk > 5 y was admitted for a fracture. Forty-five percent of elk with fractures were admitted during August and September; the rest were distributed throughout the year.

Diarrhea was the second most common diagnosis. Only 10% of the elk diagnosed with diarrhea had an etiological agent identified; these included enterotoxigenic Escherichia coli (80%), Cryptosporidium parvum (10%), and Salmonella spp. (10%). Elk diagnosed with diarrhea had a 40% in-hospital case fatality rate. There was no statistically significant risk or trend between diarrhea and survival. Elk diagnosed with diarrhea were between the ages of 3 d and 1 mo in 84% of the cases. No cases of diarrhea were seen during December or January; most (62%) cases were seen in June.

Umbilical disease was represented by umbilical hernias (n = 11, 85%) and omphalophlebitis (n = 2, 15%); it carried an excellent prognosis with only an 8% in-hospital case fatality rate. Umbilical disease was not diagnosed in elk < 3 wk; most (61%) were diagnosed in elk aged 3 to 5 mo, which corresponded to the months of presentation (June through September). There was a reduced risk of death with umbilical disease (odds ratio = 0.7), but this was not statistically significant (P = 0.066).

Cerebellar abiotrophy was the most commonly diagnosed central nervous system (CNS) disease (n = 5, 45.5%), other CNS diseases included hepatic encephalopathy (n = 3), cerebral abscess (n = 1), and cerebral hematoma (n = 1). Chronic wasting disease, although suspected in a number of cases, was not diagnosed in any elk. Copper deficiency, ryegrass staggers, or toxins were also not detected. Elk diagnosed with a CNS lesion carried a grave prognosis, as there was a 90% in-hospital case fatality rate associated with such a diagnosis. There was a statistically significant increased risk of death with CNS disease (odds ratio = 7.59, P ≤ 0.0001). No age group was preferentially affected by CNS disease; however, elk > 3 y were not diagnosed with such a disease. Cases of CNS disease were diagnosed with the highest frequency (73%) in June through September.

Urogenital problems were restricted to preputial and penile lacerations or prolapses, and there were no in-hospital case fatalities associated with such a diagnosis. There was no statistically significant risk or trend between urogenital disease and survival. Eighty percent of urogenital problems were diagnosed in elk ≥ 1 y. Fall and winter were the only seasons in which such problems were diagnosed.

Rectal and anal problems included fistulas (n = 5), anal strictures (n = 3), rectal prolapses (n = 1), and atresia ani (n = 1). Some elk had multiple rectal and anal problems, such as fistulas and strictures. The in-hospital case fatality rate with such a diagnosis was only 12.5%. There was no statistically significant risk or trend between elk with rectal problems and survival. Rectal and anal disorders were diagnosed throughout the year and 80% of cases occurred in patients that were ≥ 1 y.

Pulmonary disease occurred mostly (70%) in conjunction with other diseases. Bronchopneumonia was the most common pulmonary disease (n = 9, 61.5%). The etiological cause of the bronchopneumonia was determined in too few cases to be discussed, and verminous pneumonia was never diagnosed. Other diagnoses included aspiration pneumonia (n = 3, 23%) and other (pulmonary edema, pulmonary atelectasis) (n = 2, 15.5%). Pulmonary disease carried a guarded prognosis with a 64% in-hospital case fatality. Elk with pneumonia had a statistically significant increased risk of death (odds ratio = 1.76, P = 0.037). Pulmonary disease was noticed exclusively in elk aged < 1 y; 86% of cases were ≤ 1 mo. Elk with such a diagnosis were seen exclusively in the months between May and September, inclusive, with 54% occurring in June alone.

Elk with septicemia had multiple organ failure/disease, and most had concurrent diarrhea and pneumonia. There was a 100% in-hospital case fatality rate associated with septicemic elk. Elk with septicemia had a statistically significant increased risk of death (odds ratio = 21.1, P ≤ 0.0001). Elk of all ages appeared to succumb to septicemia, but there was predilection for younger elk with 65% aged < 1 mo. Most cases (71%) were seen in the months of May through July.

Musculoskeletal problems, other than fractures, were common diagnoses (n = 33, 11.8%). The most common problems included septic arthritis (n = 8), osteomyelitis (n = 8), capture myopathy (n = 7), angular limb deformities (n = 2), laminitis (n = 2), ruptured tendons (n = 2), tenosynovitis (n = 1), and of unknown cause (n = 3). These diagnoses had a 36% in-hospital case fatality rate. There was no statistically significant risk or trend between elk with these diagnoses and survival. Thirty-six percent of affected elk were between 2 wk and 4 mo of age, and 55% were between 1 and 6 y of age. These problems were diagnosed throughout the year, but 33% occurred in September alone.

The most common ocular diagnoses were stromal abscesses (n = 3), corneal ulcers (n = 2), proptoses (n = 2), and anterior uveitis (n = 1). Ocular disease was associated with a 14% in-hospital case fatality rate. There was no statistically significant risk or trend between ocular disease and survival. Seventy percent of ocular diseases were seen in elk aged between 4 and 7 mo, with the range being 2 wk to 1 y. Most cases (86%) were diagnosed in the months of October and November.

All integumentary wounds were diagnosed as being due to trauma. There was a 25% in-hospital case fatality rate associated with integumentary diagnoses. There was no statistically significant risk or trend between integumentary wounds and survival. Integumentary wounds were not significantly associated with any age group. Elk were presented with integumentary wounds throughout the year.

“Other” diseases were collectively the second largest diagnostic group, and comprised a highly varying number of diagnoses, including emaciation (n = 8), metabolic disorders (n = 4), grain overload (n = 4), neoplasia (n = 3), necrobacillosis (n = 3), parasitism (n = 3), cardiac anomalies (n = 3), rumenitis (n = 2), neonatal problems such as immaturity (n = 3), hypoglycemia (n = 2), and starvation (n = 2). Several other diseases were diagnosed all in single animals.

Discussion

As with in any retrospective case series, this study has limitations. Most importantly, the disease frequencies may not reflect those seen by farmers in the field as simple cases and treated by the owner without veterinary assistance. However, the data are likely to be helpful to veterinarians called to treat sick elk, as the cases described here were presented for this reason. One advantage of this case series is the wide range of ancillary testing available in the WCVM hospital setting to assist diagnosis. Furthermore, as a matter of policy, almost all cases that died in-hospital were submitted for necropsy. Both factors would have helped to increase the rate of diagnosis; only 3.7% of cases admitted were undiagnosed.

The high ratio of young elk admitted to the clinic probably explains why the months with the highest caseloads were June, July, and September. Calving in elk occurs in June and July, so this period encompasses the neonatal to weaning and rutting periods. Diarrhea, umbilical disease, pulmonary disease, and septicemia were the major diagnostic categories in very young elk that presented mostly during the summer months.

Fractures and other musculoskeletal problems were other conditions that young elk were disposed to, especially during the late summer and early fall growing stages. Fractures seen were mostly as traumatic catastrophic comminuted long bone fractures in young to young adult elk that occurred towards the end of summer and into the fall. This agrees with a study of limb amputations by Butt et al (2), in which all elk < 6 mo and 11 out of the 13 in total had catastrophic comminuted long bone fractures. Fractures are most likely due to the increased handling of elk at this age and because of fighting associated with the onset of the rutting season in September through October. Other musculoskeletal diseases, such as capture myopathy and ruptured tendons, were also noticed in young to young adult elk towards the end of summer and early fall, probably for similar reasons. Fractures and other musculoskeletal problems, which have been documented in farmed elk (1,2,4), carry a good prognosis in the WCVM hospital setting, which is most likely due to treatment options that are now available such as limb amputation in female elk (2).

Diarrhea presented mostly as acute, undifferentiated neonatal diarrhea with 84% of cases occurring in the 1st mo of life. The etiological agents isolated in this study, enterotoxigenic E. coli, Salmonella spp., and C. parvum, are similar to those in calves (5). An etiological diagnosis was rarely established, as etiological diagnosis was made in only 10% of the cases. Diarrhea was seen to have a fair prognosis in elk, as the in-hospital fatality rate was 40%. A recent study shows a case fatality rate of 8.6% for diarrheic bovine calves (unpublished observations). The higher mortality in elk calves may be due, in part, to the presence of hypernatremia associated with diarrhea in some elk calves, which can complicate treatment and worsen the outcome (6). High mortality due to difficulty in specific treatment of an etiologic agent, such as C. parvum, is also acknowledged. Having farmers notice and respond early to cases of diarrhea in elk calves is a problem, and earlier intervention may improve the prognosis.

Young elk were prone to pulmonary disease, septicemia, and umbilical disorders, such as hernias and omphalophlebitis. Pulmonary disease, largely seen as bronchopneumonia or aspiration pneumonia, was usually concurrent with other diseases, such as diarrhea, septicemia, or both. Aside from umbilical problems, diseases of neonatal and young elk were largely of infectious nature and carried a guarded prognosis. Pople et al (3) also found a high frequency of infectious diseases in a necropsy study of young elk. While most disease in very young calves were infectious, noninfectious diseases were also documented such as mis-mothering, immaturity, starvation, and hypoglycemia. Other studies (3, 7) have also reported such problems in young elk calves. These problems present a challenge for elk farmers to respond to, more so than farmers of domesticated ruminant species, due to the relatively nondomesticated nature of elk. Elk are more fractious to handle than domesticated species and female elk are known to hide their calves (1), which makes it difficult for farmers to tend to their young.

Older elk have more noninfectious diseases, such as traumatic injuries; other musculoskeletal problems, such as arthritis, laminitis, and lameness; penile and preputial lacerations and prolapses; and rectal fistulas, strictures, and prolapses. This may be the result of their heavier weight, more aggressive nature, and breeding purposes. A total of 59 elk admitted were > 1 y, and their diseases carried a similar prognosis to disease in younger elk. Most of the deaths were cases of extensive limb fractures, such as bilateral comminuted humeral fractures and bilateral metatarsal fractures.

Overall, the prognosis of elk admitted to the WCVM is good, as 66.5% were discharged alive. The mortality may be reduced as veterinarians become more adept at treating farmed elk. This study could further improve prognosis by making veterinarians aware of the common problems of elk, thus facilitating diagnosis and treatment.

This is the first known report of the diseases diagnosed in elk admitted to a large animal clinic along with their seasonality and predilection for certain age groups. Practitioners can use this information to predict diseases and mortality, which should improve the provision of veterinary services to this new industry. CVJ