Reindeer Die from West Nile Virus

Reindeer owners have frequently heard that “cervids are cervids” or “deer are deer.” From anecdotal experience, we believe that reindeer respond differently than many other cervids to various disease and testing situations.

Presentations during annual USAHA meetings have demonstrated that these experiences are being validated by scientific studies.

Last year USDA APHIS veterinarians, Drs Mike Philo and Linda Carpenter, indicated to the TB committee that a study at the U of Alaska at Fairbanks confirmed that “reindeer do not respond predictably or consistently to the CCT.” As a continuation to that study, 19 castrated reindeer bulls were delivered to NVSL to be housed next door at NADC (National Animal Disease Center) in Ames, Iowa in May 2002.

At the 1999 Wildlife Diseases committee meeting at San Diego, I listened to Dr Bob Cook’s presentation regarding West Nile Virus in New York and the disease’s impact and bird losses for the Wildlife Conservation Society/Bronx Zoo. I was particularly interested in this presentation because I provide 8 reindeer annually to the Bronx Zoo for their Christmas season festival of lights exhibition.

At the 2001 Captive Wildlife and Alternative Livestock committee meeting, Ethel Evans, then president of ROBA, and I listened to Dr. Tracey McNamara’s informative presentation on “Bridging the Gap” between various agencies regarding West Nile Virus. We were quite interested in Dr. McNamara’s comments regarding cases of WNV showing that initial assumptions of the disease and its effects were wrong.

ROBA members have been speaking with veterinarians and wildlife biologists in various agency positions since 1999 regarding WNV and the possible effects to their reindeer and herds. The overwhelming response from that community was that reindeer should not be expected to contract WNV.

On September 6 and 7 of this year I experienced the sudden deaths of two five-month old reindeer calves in excellent condition at my leased farm in Taylor’s Falls MN. The first calf, a heifer, was sent to the WI diagnostic lab at Barron WI, about 40 miles away. The animal was not tested for WNV and cause of death was not definitively determined. The second death, a male, occurred early the next morning, on a Saturday. A necropsy was done by my vet (Dr. John Springer) in high temperature and humidity with samples sent to Barron on Monday. The cause of death was not definitively determined. The animal was not tested for WNV.

About a week later, on September 12th in the late afternoon, I observed a 10 1/2 yr old reindeer bull on my farm at Milltown, Wisconsin in an apparently weakened condition with ears down and at times staggering. That Wisconsin farm is about 7-8 miles from the MN farm, across the St. Croix River, which acts as the border between the 2 states.

His condition did not improve overnight. He went down about 5 am on the 13th, was in rut, and was euthanized a few hours later. He was sent, intact, to the Barron lab. He was not tested for WNV. The brain stem was sent to NVSL for CWD testing, as required by Wisconsin rules.

When the reindeer bull was euthanized, we suspected brainworm may have been a possible cause of the symptoms. After all, cervids and reindeer were not expected to contract or exhibit symptoms of WNV. CWD testing subsequently indicated that no prions were evident. The cause of death was not definitively determined.

Later on that same day, Friday, the 13th of September, I observed a 12 1/2 year old gelding reindeer that was in the same pen as the euthanized bull exhibiting similar symptoms. Since he could still walk, he was led to a large trailer for confinement and treatment for brainworm. He was kept alive for 10 days with supportive treatment, ampicillian, Ivomec, banamine, Vitamin B complex, and dexamethazone. After 3 days of treatment he appeared to improve, and continued to eat and drink, but then began to fail as paralysis continued to progress.

During the treatment period we began to suspect WNV. He died on Sunday, September 22. I had previously decided, since he and I had been constant companions for more than a dozen years, that he would not be carted off in a rendering truck from the lab, but would be buried on the farm, in the pen in which he had lived.

The brain, as required, and blood samples were delivered to the Barron Lab the next day, for further transfer to NVSL. The gelding was sero and PCR positive for WNV.

On October 1st, I was informed by Dr. Mitch Palmer that 3 of the 19 reindeer delivered to NVSL in May had died of WNV.

Those reindeer, housed at NADC, are on pastures adjacent to or near pastures containing elk, white-tailed deer, bison, cattle, sheep and horses. However, to date, clinical signs have only been seen in the reindeer.

Those 3 deaths occurred on September 20, 24, and 27, 2002.

  1. Two were found febrile, in lateral recumbency with tetraplegia (all 4 limbs paralyzed).
  2. A third was febrile, depressed, head tilt, flaccid tongue with dysphagia (difficult swallowing), progressing to tetraplegia within 12 hours.
  3. Brains were PCR positive at NVSL.
  4. Histology – mild lymphocytic perivascular cuffing and edema, gliosis and lymphocytic infiltrates. Lesions most pronounced in medulla although still categorized as mild to moderate. Spinal cord also contained perivascular lymphocytic cuffing and marked myelin sheath swelling. Myocardium contained mild multifocal areas of myofiber degeneration/necrosis with little inflammation.
  5. WNV IHC showed mild staining limited to the brain stem and spinal cord.
  6. CBCs on the September 24 and 27 deaths indicated elevated fibrinogen, stress leukogram, and lymphopenia – consistent with a viral infection.

Some ROBA members have observed similar symptoms in reindeer that have died this past summer and earlier, but were not tested for WNV.

Many, if not most, of our herds are in mandatory or voluntary CWD monitoring programs requiring the brain stem of adult animals for CWD testing. That tissue is also, as I understand, the tissue of choice for WNV testing. This is a dilemma for the reindeer owner whose species is one of 34 that has yet to exhibit CWD but appears very susceptible to WNV, while other cervids may not be.

A review of the federal response time for our TB testing problems can be used to point out the difficulties that our industry has previously suffered. There is no reason to repeat this scenario. We believe USDA APHIS can ensure the appropriate pathologists are aware of reindeer susceptibility to WNV when examining brain stems for CWD. This may have already been accomplished.

Any assistance by USDA or other agencies in developing, recommending and testing an appropriate vaccine for reindeer for WNV would be greatly appreciated.

Source: Tom Scheib, Vice President of the 200-member Reindeer Owners and Breeders Association (ROBA) with reindeer farms in Milltown, Wisconsin and Taylor’s Falls, Minnesota.