Wildlife diseases: WGFD explains wasting diseases

Casper – Justin Binfet, wildlife management coordinator with Wyoming Game and Fish Department (WGFD) provides an update on chronic wasting disease (CWD) and epizootic hemorrhagic disease (EHD) affecting Wyoming wildlife.  

Chronic wasting disease 

                  CWD is a type of transmissible spongiform encephalopathy, or prion disease, and is essentially a mutated or misfolding protein found in the central nervous system, explained Binfet. This disease causes adjacent proteins to misfold and ultimately causes the death of cells.  

                  “It’s a disease that spreads throughout the nervous system and ultimately the brain,” said Binfet. “Unfortunately, CWD is always fatal, resulting in death of the animal.”         

                  He noted there are similar prion diseases – fatal brain diseases which can affect livestock, and even humans, such as mad cow disease, scrapie disease in sheep or Creutzfeldt-Jakob disease in humans. 

                  Fortunately, CWD only affects members of the deer family, shared Binfet. 

                  “In Wyoming, mule deer, white-tailed deer, elk and moose can be affected by CWD. It does not affect antelope, Bighorn sheep or livestock,” said Binfet. “It can be spread from animal to animal through bodily fluids, with prions also being shed through feces and urine, which can contaminate the soil and environment.” 

                  Binfet noted the incubation period for CWD can range from a year and half to three years, depending on the genetic make-up of the animal. 

                  “It’s a slow progressing disease, so an animal that is infected with CWD will not exhibit any clinical symptoms for the first year or more, but when they do, they start to lose weight and behavioral awareness, and they eventually die,” explained Binfet. 

                  He noted, CWD is a prion disease, not a virus or bacteria. 

Epizootic hemorrhagic disease 

                  Another significant type of disease that has been prevalent this year in Wyoming wildlife – with the most pronounced effects on white-tailed deer – is epizootic hemorrhagic disease, both EHD and blue tongue.

                  Binfet noted there has been a significant outbreak of EHD and blue tongue due to persistent drought conditions, which impacted both white-tailed deer and antelope populations in many areas, and may have even impacted mule deer in some regions.   

                  “Blue tongue and EHD are almost identical. They are both viral diseases which are spread and transmitted by little biting insects, but most commonly by a biting midge,” explained Binfet. “There are multiple strains of each one, but the viruses act the same in susceptible animals.”

                  Binfet continued, “During really dry summers and early falls, animals tend to concentrate more around fewer available water sources, which often become stagnant during a hot, dry summer. This creates ideal breeding habitat for the midges.  EHD is more pronounced during dry years and warm falls.” 

                  This year was exceptionally warm and dry until mid-October, and many parts of Wyoming did not get a hard freeze in September like normal, Binfet noted. 

                  EHD doesn’t typically occur until late summer and early fall – usually in August and September. This year, the outbreak persisted well into October with numerous reports of dead deer being fielded from landowners and sportsmen.

                  “We never know until right before hunting season if wildlife are going to be affected,” said Binfet. “There are parts of the state where we’ve had some of the worst EHD and blue tongue outbreaks that we have documented in several decades.”  

Binfet noted EHD and blue tongue outbreaks are typically localized, but this year they have been widespread.  

Outbreak precautions 

                  While there is not a concern of CWD or EHD amongst livestock, there are strains of blue tongue which can affect cattle and domestic sheep. Binfet recommends producers contact the state veterinarian’s office with concerns and more information on the strains, which affect livestock. He adds, EHD and blue tongue will not be transmitted by wildlife, but instead insects. 

                  “When EHD and blue tongue outbreaks happen, it kills deer or antelope fairly quickly,” Binfet said. “It either kills them in less than a week or sometimes they survive. It’s not always fatal.”

                  It can also kill a large amount of wildlife in a localized area.  WGFD works to document the outbreak, location within the state and work alongside the state veterinarian.  

                  “This year WGFD has documented a significant number of white-tail deer and antelope which have been affected by EHD,” he added. 

                  Infected carcasses are sent to the Wyoming State Vet Lab to be tested. If wildlife from an area tested positive, that information can be found on the WGFD website, as well as information regarding outbreak mitigation. 

WGFD programs

                  There is a comprehensive testing, surveillance and monitoring program for CWD amongst hunter-harvested animals. 

                  Active hunters are encouraged to contact WGFD by calling their offices or checking the website for current impacted priority surveillance areas. 

                  “We don’t have the capacity to test every harvested deer or elk around the state, so what we’re trying to do is extensively sample all of Wyoming’s deer and elk herds on a rotating basis every five years,” explained Binfet. “We ask folks to pay attention to priority surveillance areas, and if they are hunting in one of our designated priority herds, we ask them to do what they can to contribute to our sample goal by having their deer or elk tested.”

                  He continued, “With respect to EHD and blue tongue, there’s nothing hunters can do outside of reporting wildlife death.”             

Consumption of infected wildlife

                  “WGFD adopts measures that come from the Centers of Disease Control and the World Heath Organization, which suggest if hunters harvest a deer or elk that tests positive for CWD, they do not consume it,” Binfet said. “There’s never been a demonstrated case of humans acquiring CWD, but that’s their recommendation and we follow it.”  

                  “With respect to EHD and blue tongue, there’s no human or pet health concerns associated with those,” said Binfet   

                  Binfet explains the West Nile virus has the ability to affect humans and livestock. He notes a concern for the WGFD is sage grouse death, and encourages this to be reported. 

Through the years

                  “CWD is really unfortunate,” said Binfet. “Since we’ve first discovered it in wildlife populations in the mid-80s, we’ve seen it progress throughout the state and spread to all corners of Wyoming with the exception of the extreme southwestern part of the state.”  

                  It has been observed that CWD is consistently taking a large toll on wildlife populations, whereas EHD and blue tongue show up periodically.

                  “CWD is becoming an epidemic within the population and essentially is continuing to run through deer and elk herds year-in and year-out. It’s having a negative long-term impact on deer populations in certain areas, and may even begin to impact elk if prevalence continues to increase,” said Binfet. “This is concerning for the long-term productivity of mule deer herds and white-tailed deer herds in some cases.” 

                  Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.