Transmission of sheep scrapie to elk (Cervus elaphus nelsoni) by intracerebral inoculation: final outcome of the experiment.

This is a final report of an experimental transmission of sheep scrapie agent by intracerebral inoculation to Rocky Mountain elk (Cervus elaphus nelsoni). It documents results obtained in experimental (n = 6) and control (n = 2) elk. During the first 2 years postinoculation (PI), 3 animals died or were euthanized because of infection or injuries other than spongiform encephalopathy (SE). In years 3 and 4 PI, 3 other inoculated elk died after brief terminal neurological episodes. Necropsy of these animals revealed moderate weight loss but no other gross lesions. Microscopically, characteristic lesions of SE were seen throughout the brain and spinal cord, and the tissue was positive for proteinase K-resistant prion protein (PrPres) by immunohistochemistry (IHC) and by Western blot. Scrapie-associated fibrils (SAF) were observed by negative-stain electron microscopy in the brain of elk with neurologic signs. PrPres and SAF were not detected in the 3 inoculated elk necropsied during the first 2 years or in the 2 control animals. Retrospective analysis of the gene-encoding cervid PrP revealed a polymorphism at codon 132. The elk with SE were either homozygous (MM) or heterozygous (LM). These findings confirm that intracerebral inoculation of sheep scrapie agent results in SE with accumulations of PrPres in the central nervous system of elk. Based on morphologic and IHC findings, the experimentally induced SE cannot be distinguished from chronic wasting disease of elk with currently available diagnostic techniques.     

Preliminary observations of genetic susceptibility of elk (Cervus elaphus nelsoni) to chronic wasting disease by experimental oral inoculation.

To compare the genetic susceptibility of elk (Cervus elaphus nelsoni) with various alleles of the PRNP gene, which encodes the normal cellular prion protein, to chronic wasting disease (CWD), eight 8-month-old elk calves of 3 genotypes (2 132MM, 2 132LM, and 4 132LL) were orally dosed with CWD-infected brain material from elk. During postinoculation (PI) month 23, both 132MM elk had lost appetite, developed clinical signs of weight loss and central nervous system (CNS) dysfunction, and were euthanized. Two other elk (both 132LM) developed similar clinical signs of disease and were euthanized during PI month 40. All 4 affected elk had microscopic lesions of spongiform encephalopathy (SE), and PrPres, the disease-associated form of the prion protein, was detected in their CNS and lymphoid tissues by use of immunohistochemical (IHC) and Western blot (WB) techniques. These findings indicate that elk with MM and LM at codon 132 are susceptible to orally inoculated CWD. All 4 LL elk are alive at PI year 4 and are clinically normal, which suggests that 132LL elk may have reduced susceptibility to oral infection with CWD-infected material or may have prolonged incubation time.     

Evaluation of vaginal implant transmitters in elk (Cervus elaphus nelsoni).

The effects of vaginal implant transmitters for tissue damage after 11 wk in 13 captive adult elk (Cervus elaphus nelsoni) and subsequent reproductive performance in 38 free-ranging elk were evaluated. Vaginal implant transmitters are designed to be shed at parturition and are used to locate birth sites of wild ungulates; however, potential adverse effects of these transmitters on tissues associated with the vaginal walls or subsequent reproductive performance have not been assessed. Vaginal implant transmitters consist of a transmitter encased in inert acrylic with an antenna trailing out the distal end and wings at the proximal end to hold the transmitter in place. Using a laparoscope on sedated captive elk, necrosis or measurable differences in tissue trauma between designs with wing spans of 80 versus 150 mm over an 11-wk trial were not observed. After the captive elk trial, vaginal implant transmitters with 80-mm wings were placed into 38 pregnant wild elk, and 31 live births were documented. Fates of seven calves were not determined, because their transmitters were not shed at the birth site. We recaptured 36 of these cow elk again in fall 2003 or spring 2004, and 32 were pregnant. This study was unable to document any short- or long-term effects of vaginal implant transmitters on reproductive performance of cow elk in captive and free-range environments.     

Experimental transmission of chronic wasting disease (CWD) of elk (Cervus elaphus nelsoni), white-tailed deer (Odocoileus virginianus), and mule deer (Odocoileus hemionus hemionus) to white-tailed deer by intracerebral route

To compare clinical and pathologic findings of chronic wasting disease (CWD) in a natural host, 3 groups (n = 5) of white-tailed deer (WTD) fawns were intracerebrally inoculated with a CWD prion of WTD, mule deer, or elk origin. Three other uninoculated fawns served as controls. Approximately 10 months postinoculation (MPI), 1 deer from each of the 3 inoculated groups was necropsied and their tissues were examined for lesions of spongiform encephalopathy (SE) and for the presence of abnormal prion protein (PrP(d)) by immunohistochemistry (IHC) and Western blot (WB). The remaining deer were allowed to live until they developed clinical signs of the disease which began approximately 18 MPI. By 26 MPI, all deer were euthanatized on humane grounds. Obvious differences in clinical signs or the incubation periods were not observed between the 3 groups of deer given CWD. In 1 of 3 nonclinical deer euthanatized at 10 MPI, minimal microscopic lesions of SE were seen in the central nervous system (CNS) tissues, and PrP(d) was observed by IHC in tissues of all 3 deer. In the clinical deer, CNS lesions of SE and PrP(d) accumulations were more severe and extensive. It is concluded that the 3 sources of CWD prion did not induce significant differences in time to clinical disease or qualitative differences in signs or lesions in WTD. However, this observation does not imply that these CWD agents would necessarily behave similarly in other recipient species.     

Abomasal and uterine adenocarcinomas with ovarian metastasis in a captive elk (Cervus elaphus nelsoni).

A captive, 20-year-old female elk (Cervus elaphus nelsoni) euthanized due to progressive lameness and weight loss was presented to Colorado State University Veterinary Diagnostic Laboratory for postmortem examination. Within the uterus there was a poorly demarcated, multilobulated mass measuring 10 cm in diameter. Histologically the tumor was an adenocarcinoma. Histologic examination of the ovaries revealed unilateral metastasis. A focal, 1-cm diameter adenocarcinoma was identified within the abomasum; this tumor was histologically distinct from the neoplasm found in the uterus and ovary. Although this elk had a history of experimental reproductive treatments, including leuprolide, gonadotropin-releasing hormone vaccine, and Brucella abortus vaccination, it was most likely that both tumors represent spontaneous, independent neoplastic transformations and were unrelated.     

Laminitis in a mature elk hind (Cervus elaphus)

Laminitis should be considered as a differential diagnosis in elk presenting with shifting leg lameness, reluctance to move, recumbency and hoof wall ridging. Eliminating the underlying cause and corrective trimming lead to a good prognosis for recovery.     

Effects of supplemental feeding on gastrointestinal parasite infection in elk (Cervus elaphus): preliminary observations

The effects of management practices on the spread and impact of parasites and infectious diseases in wildlife and domestic animals are of increasing concern worldwide, particularly in cases where management of wild species can influence disease spill-over into domestic animals. In the Greater Yellowstone Ecosystem, USA, winter supplemental feeding of Rocky Mountain elk (Cervus elaphus) may enhance parasite and disease transmission by aggregating elk on feedgrounds. In this study, we tested the effect of supplemental feeding on gastrointestinal parasite infection in elk by comparing fecal egg/oocyst counts of fed and unfed elk. We collected fecal samples from fed and unfed elk at feedground and control sites from January to April 2006, and screened all samples for parasites. Six different parasite types were identified, and 48.7% of samples were infected with at least one parasite. Gastrointestinal (GI) nematodes (Nematoda: Strongylida), Trichuris spp., and coccidia were the most common parasites observed. For all three of these parasites, fecal egg/oocyst counts increased from January to April. Supplementally fed elk had significantly higher GI nematode egg counts than unfed elk in January and February, but significantly lower counts in April. These patterns suggest that supplemental feeding may both increase exposure and decrease susceptibility of elk to GI nematodes, resulting in differences in temporal patterns of egg shedding between fed and unfed elk.     

Pharmacokinetics of florfenicol in North American elk (Cervus elaphus)

Florfenicol pharmacokinetics after administration of a single subcutaneous (s.c.) dose of 40 mg/kg of body weight in adult elk (Cervus elaphus) was investigated. Serum florfenicol concentrations were determined by a sensitive high-performance liquid chromatographic method with limit of quantification of 0.03 microg/mL. Florfenicol pharmacokinetic parameters in elk were estimated using a noncompartmental approach. After a single s.c. injection, florfenicol concentrations remained above 1 microg/mL for approximately 36 h and above 0.5 microg/mL for approximately 72 h. Following s.c. injection, florfenicol was absorbed rapidly with a mean maximum concentration (C(max)) of 3.7 microg/mL achieved at 4.2 h (T(max)). The C(max) value in elk is similar to values reported in cattle at the same dose, suggesting that the 40 mg/kg s.c. dose achieves therapeutic concentrations in elk. A mean elimination half-life (t(1/2)) of 44 h is shorter than that reported in cattle. The more rapid elimination half-life in elk suggests that elk may require a multiple dose regimen for therapeutic success with s.c. Nuflor. We recommend s.c. Nuflor be administered subcutaneously to elk every 24 h at a dose level of 40 mg/kg.     

Genetic variation in domestic and wild elk (Cervus elaphus)

Elk (Cervus elaphus) have recently been established as domestic livestock derived from extant wild populations and may provide insights into changes in genetic variation during domestication. We compared genetic variation at 10 microsatellite DNA loci and the mitochondrial DNA D-loop in 2 herds of domestic elk in Alaska and Canada and wild elk from 8 locations in western North America and Asia. Average individual heterozygosity was 0.55 in domestic elk and 0.47 in wild elk, average number of alleles per locus was 4.1 in domestic elk and 3.9 in wild elk, and 4 mitochondrial DNA haplotypes were observed in domestic elk and 3 in wild elk. Levels of genetic variation were not significantly different among the domestic elk and wild elk we analyzed. Our results are consistent with other studies showing that genetic variation can be maintained in domestic and wild populations of elk and other deer with appropriate management.     

Experimental transmission of scrapie agent to susceptible sheep by intralingual or intracerebral inoculation

Scrapie, a transmissible spongiform encephalopathy (TSE), is a naturally occurring fatal neurodegenerative disease of sheep and goats. This study documents survival periods, pathological findings, and the presence of abnormal prion protein (PrP(Sc)) in genetically susceptible sheep inoculated with scrapie agent. Suffolk lambs (AA/RR/QQ at codons 136, 154, and 171, respectively) aged 4 mo were injected by the intralingual (IL) or intracerebral (IC) route with an inoculum prepared from a pool of scrapie-affected US sheep brains. The animals were euthanized when advanced clinical signs of scrapie were observed. Spongiform lesions in the brain and PrPsc deposits in the central nervous system (CNS) and lymphoid tissues were detected by immunohistochemical and Western blot (WB) testing in all the sheep with clinical prion disease. The mean survival period was 18.3 mo for the sheep inoculated by the IL route and 17.6 mo for those inoculated by the IC route. Since the IC method is occasionally associated with anesthesia-induced complications, intracranial hematoma, and CNS infections, and the IL method is very efficient, it may be more humane to use the latter. However, before this method can be recommended for inoculation of TSE agents, research needs to show that other TSE agents can also transmit disease via the tongue.     

Abomasal parasite syndrome in North American elk (Cervus elaphus canadensis)

CASE HISTORY An 18-month clinical course of chronic ill-thrift, weight loss and emaciation, and eventual death occurred in a group of 520 translocated elk of mixed age and sex. Trans-location was carried out without regard to animal welfare or health risks associated with the translocation. Mortality was approximately 84% (436/520) despite supportive nutritional and medical treatment.

PATHOLOGICAL FINDINGS: General clinical and post-mortem examinations indicated only Se and Cu imbalances and nutritional inadequacy. Additional purposeful post-mortem examination and histological evaluation of tissue sections from four of the affected adult elk demonstrated elevated abomasal pH and proliferative abomasal lesions as the most significant findings, consistent with Type-II ostertagiosis; intra-lesional nematodes were seen in the abomasum of two animals.

DIAGNOSIS: Fading elk syndrome, or abomasal parasite syndrome in elk.

CLINICAL RELEVANCE: Abomasal parasite syndrome initiated by Type-II ostertagiosis should be considered as a differential diagnosis in cases of ill-thrift and wasting in elk or elk-red deer hybrids. Changes to the architecture and secretory function of the abomasal wall lead to apparently irreversible digestive pathophysiology and nutritional disease.     

Cholangiectasis and duodenal diverticulosis in a farm-raised elk (Cervus elaphus)

A 6-year-old male elk presented in August with a 4-month history of weight loss and a 1-day history of being recumbent and unable to rise. The elk's body condition score was 1.5/5. Hematology and blood chemistry showed an inflammatory leukogram, mild electrolyte abnormalities, and elevated liver enzyme activities. Because of poor prognosis, the owner elected euthanasia. On necropsy, 8 diverticula were in the duodenum distal to the common bile duct, which was dilated and filled with feed material. Many intrahepatic bile ducts were dilated up to 5 cm, were filled with ingesta and gritty material, and had walls thickened up to 1.5 mm. On histologic examination, mural thickening of dilated bile ducts was because of increased fibrous connective tissue with inflammatory cell infiltration and hyperplastic and hypertrophic epithelial lining. Portal tracts diffusely contained hyperplastic bile ducts and had increased amounts of fibrous connective tissue. Abscesses that contained bacteria were scattered throughout the liver. Duodenal diverticula lacked the tunica muscularis, and the muscularis mucosa was hypertrophied. Caudal to some diverticula, the duodenal lumen was narrowed. An additional finding was embolic pneumonia with fungi morphologically and immunohistochemically consistent with Aspergillus spp.     

Detection of PrP(CWD) in postmortem rectal lymphoid tissues in Rocky Mountain elk (Cervus elaphus nelsoni) infected with chronic wasting disease.

Preclinical diagnostic tests for transmissible spongiform encephalopathies have been described for mule deer (Odocoileus hemionus), using biopsy tissues of palatine tonsil, and for sheep, using lymphoid tissues from palatine tonsil, third eyelid, and rectal mucosa. The utility of examining the rectal mucosal lymphoid tissues to detect chronic wasting disease (CWD) was investigated in Rocky Mountain elk (Cervus elaphus nelsoni), a species for which there is not a live-animal diagnostic test. Postmortem rectal mucosal sections were examined from 308 elk from two privately owned herds that were depopulated. The results of the postmortem rectal mucosal sections were compared to immunohistochemical staining of the brainstem, retropharyngeal lymph nodes, and palatine tonsil. Seven elk were found positive using the brainstem (dorsal motor nucleus of the vagus nerve), retropharyngeal lymph nodes, and palatine tonsil. Six of these elk were also found positive using postmortem rectal mucosal sections. The remaining 301 elk in which CWD-associated abnormal isoform of the prion protein (PrP(CWD)) was not detected in the brainstem and cranial lymphoid tissues were also found to be free of PrP(CWD) when postmortem rectal mucosal sections were examined. The use of rectal mucosal lymphoid tissues may be suitable for a live-animal diagnostic test as part of an integrated management strategy to limit CWD in elk.     

Preliminary observations on lungworms in farmed and feral red deer (Cervus elaphus) in Denmark

Deer farming is on its increase in Denmark. Based on experiences from other countries, lungworm infection is expected to cause severe problems in farmed deer. Therefore, in the present paper, which is the first one to deal with pathogens in Danish deer farms, the faecal larval excretion in red deer is examined.     

Mortality in Pennsylvania captive elk (Cervus elaphus): 1998-2006.

The necropsy records of 65 elk ranging from 1 day to 13(1/2) years of age were reviewed to determine the primary cause of death of each animal. The animal carcasses were submitted from 22 separate Pennsylvania elk farms over an approximately 8-year period. The most common causes of mortality in animals in which the cause of death was determined were gastrointestinal parasitism (21 cases), pneumonia (7 cases), enterocolitis (5 cases), malnutrition (5 cases), and rumenitis/acidosis (5 cases). The cause of death was undetermined in 4 of the 65 elk. Nematode organisms (20 cases) were the primary parasites identified in cases of mortality owing to gastrointestinal parasitism. Arcanobacterium pyogenes (3 cases), Escherichia coli (3 cases), and Streptococcus sp. (2 cases) were the most commonly isolated bacteria from the lung in the cases of pneumonia. Fungal organisms, consistent with Aspergillus sp. were present histologically within the pulmonary lesions in 5 cases. Bacterial agents associated with enterocolitis included Clostridium perfringens (2 cases), E. coli (1 case), Salmonella Newport (1 case) and Salmonella Thompson (1 case). The majority (56.3%) of the death loss in elk of known ages occurred in animals 1 year of age or less, with 71.4% of the gastrointestinal parasitism, 60.0% of the malnutrition, 60.0% of the enterocolitis, and 57.1% of the pneumonia cases occurring in animals within this age range. In conclusion, gastrointestinal parasitism, pneumonia, malnutrition, enterocolitis and rumenitis/acidosis were considered the most common causes of death in captive elk in this study.     

Variable patterns of distribution of PrP(CWD) in the obex and cranial lymphoid tissues of Rocky Mountain elk (Cervus elaphus nelsoni) with subclinical chronic wasting disease

Sections of medulla oblongata, taken at the level of the obex, palatine tonsil and medial retropharyngeal lymph node from 10,269 captive Rocky Mountain elk (Cervus elaphus nelsoni), were examined by immunohistochemical staining with monoclonal antibody for the prion protein associated with the transmissible spongiform encephalopathy of cervids, chronic wasting disease (PrP(CWD)). The protein was detected in 226 of them. On the basis of the anatomical location of the deposits in the brainstem of 183 elk, four distinct patterns of distribution of PrP(CWD) within the parasympathetic region of the dorsal motor nucleus of the vagus nerve and the adjacent nuclei were observed. Mild gross lesions of chronic wasting disease (serous atrophy of fat) were observed in only three elk, all with spongiform degeneration; the other elk were considered to be in the preclinical stage of the disease. In contrast with the relatively predictable distribution of prion protein (PrP) in the brain and cranial nodes of sheep and mule deer, the distribution of PrP(CWD) in the brain and nodes of the elk was more variable and unrelated to their PrP genotype. One hundred and fifty-five of the 226 positive elk had deposits of PrP(CWD) in the brainstem and lymphoid tissues, 43 had deposits only in the lymphoid tissue and 28 had deposits only in the brainstem.     

An estimation of reproductive performance of farmed elk (Cervus elaphus) in North America

North American farmed elk (Cervus elaphus) producers were surveyed to determine period specific rates of calving, abortion, and dystocia, and to examine the effect of reproduction-related mortality on the productivity of farmed elk. The overall calving rate was 86.3% and the calving rate for adult cows was found to be significantly higher than that for heifers. Abortions were seen on 7.6% of farms and the overall abortion rate was approximately 0.6%. Dystocia was experienced in 5.9% of births. Neonatal mortality, summer mortality, weaning mortality, and postweaning mortality rates were calculated and compared. Failure to produce a live neonate was responsible for 64% of the total reproductive loss and calf mortalities from birth to 1 year of age accounted for 36%. Failure to produce a live neonate had a more significant effect on productivity than did mortalities from birth to 1 year of age, suggesting that reproduction has a greater economic effect on elk farms than neonatal mortality.     

Evidence of Parelaphostrongylus tenuis infections in free-ranging elk (Cervus elaphus) in southern Ontario

The antemortem detection of a Parelaphostrongylus tenuis infection in a free-ranging wild elk (Cervus elaphus) in southern Ontario is documented. Postmortems on other free-ranging elk that died during 2000-2005 indicated that 59% (17/29) were infected with P. tenuis, based on presence of lesions in the brain.     

Experimental transmission of malignant catarrhal fever to red deer (Cervus elaphus)

Abstract

Malignant catarrhal fever was transmitted from affected to recipient red deer (Cervus eluphus) using bloodor lymphoid suspension as inoculum. Incubation periods ranged from 11 to 26 days. The disease was also transmitted using lymphoid suspension stored overnight at 4°C or at ?70°C for 8 months.

The experimental disease was characterised by fever, depression, anorexia, diarrhoea and dysentry. The course of the disease was approximately 96 hours.

Major lesions consisted of acute mesenteric lymphadenitis and acute haemorrhagic typhlitis and colitis. Lesions in the caecum and colon started as multifocal mucosal haemorrhages and progressed rapidly to massive mucosal haemorrhage.     

Experimental transmission of malignant catarrhal fever to red deer (Cervus elaphus)

Malignant catarrhal fever was transmitted from affected to recipient red deer (Cervus elaphus) using blood or lymphoid suspension as inoculum. Incubation periods ranged from 11 to 26 days. The disease was also transmitted using lymphoid suspension stored overnight at 4 degrees C or at -70 degrees C for 8 months. The experimental disease was characterised by fever, depression, anorexia, diarrhoea and dysentry. The course of the disease was approximately 96 hours. Major lesions consisted of acute mesenteric lymphadenitis and acute haemorrhagic typhlitis and colitis. Lesions in the caecum and colon started as multifocal mucosal haemorrhages and progressed rapidly to massive mucosal haemorrhage.