When it comes to containing infectious disease in wildlife, the buck stops here. Hunters for instance, are at the forefront of the Virginia Department of Game and Inland Fisheries strategy to contain Chronic Wasting Disease (CWD) in deer. The “if you see something, say something” approach has new importance with the suggestion this contagious neurological disease could infect people.
“We’re so thankful for the hunter participation we get for deer harvested in Northwestern Virginia, where we have identified CWD,” said State Wildlife Veterinarian Dr. Megan Kirchgessner. “Their participation has made it possible for us to get the data we need to monitor the spread of the disease.” She said the CWD Containment Area includes Shenandoah, Clark, Warren and Frederick Counties.
CWD belongs to a group of diseases known as “transmissible spongiform encephalopathies (TSEs).” Variations within this family of diseases include well-publicized “mad cow disease” or bovine spongiform encephalopathy (BSE). Kirchgessner said the infectious agent for CWD is a mis-folded prion (an abnormal form of a cellular protein commonly found in the deer’s central nervous system and in lymphoid tissue). While there have been no confirmed cases of CWD in Carroll County, 21 cases have been confirmed in Frederick County and one road-kill deer in Shenandoah was found to have the disease.
“Once exposed, the infectious, mis-folded prion travels to the deer’s spinal cord and brain,” Kirchgessner said. “It causes the normal prions to covert to the abnormal form causing lesions in the brain, eventually turning it into a big sponge.” This characteristic degeneration results in emaciation, abnormal behavior, loss of bodily functions and death.
She said transmission of the disease in deer typically occurs in one of two ways. The first method is from direct contact between infected and healthy deer. The second occurs indirectly by contact with saliva, urine and defecation from an infected deer. The prion can survive in soil for years and still be infectious.
Kirchgessner said studies conducted by Canadian Food Inspection Agency Prion Researcher Stefanie Czub recently were presented at a prion conference in Scotland. The results of this study have not been subjected to peer review which will not happen until the completion of the study in 2018. (The publication of scientific findings occurs only after rigorous peer review and carries more weight than preliminary data presented at a conference.)
Czub’s two-year study involved macaque monkeys, because they are a close genetic analog to humans. Three macaques were fed a meal once a month of venison collected from a confirmed CWD-positive animal along with their regular diet. The venison portion was scaled down to the body weight of the monkeys so it would be the equivalent of a 7-ounce venison steak for an average person.
According to Kirchgessner, since cooked venison is not a usual component of the monkey’s diet, the animals were sedated and the venison was administered through a feeding tube. Two of the three macaques later developed symptoms of CWD and were euthanized. A subsequent necropsy confirmed the presence of CWD prions in the spinal cord.
“Another complicating aspect of CWD is that deer can appear totally healthy for over a year before they look sick,” said Kirchgessner. “Only in the late stages is it apparent. Even when they look completely healthy, infected deer shed the CWD prion in their saliva, urine, and feces. Addtionally, the disease does not discriminate. It can hang out in the soil for years waiting for a healthy deer. It can also infect deer that are young, old, male and female.”
Deer behavior also helps spread CWD. Kirchgessner explained that male deer tend to have a higher risk of contracting the deadly prion because they can cover a lot of territory.
“It is the nature of male deer. Does (in the same family) tend to stay in limited, overlapping territory with other related females. Bucks cover a lot more ground and meet a lot of other deer along the way,” Kirchgessner said. “It is because of these differences in behavior that bucks are more likely to be infected with CWD. Infected bucks can be compared to the sparks of a flame: when these bucks travel 8 to 20 miles from the CWD fire, they have the potential to ignite new spot fires in unrelated locations.”
Kirchgessner said the Department is thankful for hunter participation in sampling efforts in Northwestern Virginia. Hunters also assist in reducing the risk of introducing CWD into new areas of Virginia by following regulations pertaining to the transportation of deer carcasses out of the counties of Shenandoah, Clark, Warren, Frederick and the importation of carcasses from out-of-state locations where CWD is known to exist.
She said vigilance among hunters and citizens is important to the effort to contain and monitor CWD and encouraged hunters to check local regulations before transporting deer carcasses. Signs of CWD in deer include abnormal behavior (i.e. no fear of humans), excessive salivation and loss of control of bodily functions.
Persons may report deer suspected of having CWD by calling the Wildlife Conflict Hotline at 1-855-571-9003. The hotline is staffed from 8 a.m. to 5 p.m., Monday through Friday.
David Broyles may be reached at 276-779-4013 or on Twitter@CarrollNewsDave.