Chronic Wasting Disease (CWD) is a deadly neurological disease that affects deer, elk, and moose. It's caused by infectious proteins known as prions and spreads from animal to animal through bodily fluids and tissues. It's been detected in much of Wyoming.
And new research from the University of Wyoming has found that this widespread disease is actually changing the genetics of the state's mule deer.
Lead author Melanie LaCava and her team partnered with the Wyoming Game and Fish Department (WGFD) and the Wyoming State Vet Lab to analyze hunter submitted samples from mule deer. After CWD testing and genetic sequencing of the samples, the researchers found a link between areas where CWD has been in mule deer herds the longest and how common a genetic mutation which slows down disease progression, known as the 225F allele, is. That mutation was found in samples from throughout the state, but it was more common in areas where CWD has been present for longer. According to LaCava, disease driven natural selection is difficult to study, but this gives strong evidence to the hypothesis that the disease is what's influencing mule deer genetics and making this mutation more common.
However, researchers are unsure what this could mean for mule deer populations. On one hand, the mutation could allow deer who have CWD to create more offspring before they die from the disease.
"So maybe the populations won't decline as much (from CWD) if this mutation becomes more common," LaCava said. "But the downside is that one of the ways that deer contract CWD is through the environment, and so if an animal's living longer, it might be the case that they're spreading these infectious prions into the environment longer, or they're coming into contact with more deer before they die. And so if that's the case, then sure, maybe that animal produces one or two more offspring, but maybe they're spreading that disease to many more deer than they would have if they died faster of CWD."
LaCava said understanding how CWD and an animal's genetics interact can help inform management decisions.
"That was one of our hopes is that this work can feed back into population models where wildlife managers are trying to predict, are populations increasing? Are they declining? How many deer can we harvest from different areas? And how does disease intersect with those kinds of decisions that they're making about management," said LaCava. "And knowing how this genetic mutation is affecting that whole network of disease dynamics can hopefully be one more piece of information that goes into those population models."
The samples the team received from the WGFD also included samples from white-tailed deer, elk, and moose. This research will continue with those other samples.
"We started with mule deer because mule deer had the highest prevalence of CWD in Wyoming and there's also been evidence of population declines associated with Chronic Wasting Disease in mule deer in the state. So it was definitely a management priority for the Wyoming Game and Fish Department and we like to target these big management issues head on," said LaCava.
Image: Tom Koerner/USFWS/Flickr