Hoof rot expert speaks to community
July 13, 2023
Dr. Margaret Wild, a professor at the Washington State University College of Veterinary Medicine, gave a presentation Monday night on the current research into the hoof rot affecting elk populations locally and in other areas in the west.
The talk was an extension of the Wahkiakum County Commissioners meeting. They were all in attendance, as well as a biologist from the Washington Department of Fish and Wildlife, Eric Holman.
In 2017, the Washington State legislature assigned WSU College of Veterinary Science to conduct research on the disease, Wild said, and their research supplements management of the disease by the WDFW.
Wild said the hoof rot is referred to as a treponeme-associated hoof disease (TAHD), and emphasized that it was treponeme-associated not treponema-caused. She said the lesions start between the toes and usually look like a little round sore.
"Our objectives are to help wildlife managers using applied research which managers can use to decrease harm from the disease," Wild said, "not cure."
Wild went over a series of questions that she is asked regularly.
Have they solved the issue yet?
"It's been five years," Wild said, "but the short answer is no."
There was a lot of controversy about contributing factors when she started, but a lot of foundational research has been done since then,
"All wildlife diseases are inherently complex," Wild said. "With domestic animals and humans, patients are often there for an appointment and can be followed through time. You can know history."
"We don't know their history, what they've been exposed to," she said of the elk. "All you have is this point and time."
She also acknowledged that treatment is challenging, because as a food producing animal, managers can't use antibiotics which could harm people harvesting the animals.
"We are just trying to learn more and mitigate the negative impacts," Wild said. "It's important to set realistic expectations."
Is the disease spreading to other species or to other areas?
They have not diagnosed TAHD in any other species, Wild said. While they receive samples of deer hooves that are deformed, it always turns out to be something else.
"Keep submitting samples through WDFW anyway," she implores hunters.
As far as location, a lot of attention was paid to southwest Washington because of a high prevalence of cases, but TAHD has been found in Oregon, Washington, Idaho, and California. Strangely enough, it hasn't been found in Canada.
There are areas where they think it might be, but they are still waiting to receive samples from those places.
"I'd really appreciate if you harvest an animal in those areas, if you would submit the hooves to WDFW, to determine if that is going on," Wild reiterated. "That allows us to monitor disease over time."
Is it really caused by bacteria?
This was a contentious matter when Wild first started. In collaboration with scientists in the United Kingdom, they have verified it's a treponema, which is a spiral shaped bacteria.
Taking tissue samples, they extracted DNA to discover what bacteria was present. It also allowed them to compare hooves with the disease with hooves without disease.
They found TAHD in the infected hooves, but there were also other bacteria present. In all their work, she said, they never found any of the family of leptospirosis.
What they couldn't do in wild animals was watch this disease take it's course, from beginning to end, so they decided to do just that with captive elk at WSU.
A research project was designed and four elk were housed in individual pens. The soil was kept moist in an effort to recreate this environment. Researchers chopped up infected hooves and placed them in soil. They also took some of that sample and placed it between the toes of the four elk, and wrapped up the hoof.
They were able to reproduce the disease in the captive elk. In four months they all had lesions. By five months three of the four elk had to be euthanized. One recovered.
"I don't know what was different about him," Wild said. "It shows that they can recover, but I don't think we should count on it in the wild. This is good strong evidence that we have a transmissible infectious disease, and more strong evidence of a cause that is bacterial."
She believes that the treponema bacteria are a hallmark of the disease, but it's likely the treponema is working in consortium with other bacteria as well.
Can other factors contribute to the disease?
Questions still remain. One thing they are considering is mineral deficiency. One is the loss of good minerals like selenium, copper, and zinc, but the addition of things like chromium, lead, and cadmium associated with herbicides could also cause potential problems.
The issue is they only have feet to sample from, Wild said. Fortunately, the feet have hair, which was collected, and a mineral analysis was done on what they had.
"Hair is not the best tissue to be running, but sometimes it's a good proxy," Wild said.
The only association they found in the study was that low selenium seemed to be associated with elk with hoof disease.
More investigation is needed, Wild said, and there are plans in the future to study the livers of infected elk.
Can we treat affected elk?
"No, not really," Wild said. "It's not logistically feasible, and we can't be putting antibiotics into the environment. There is no vaccine. These kind of veterinary cures are way down the line if at all."
Wildlife management techniques are their current course of action, she said.
What have you accomplished?
They have good, rigorous, scientific evidence to support what they thought might have been happening before, Wild said, and it's giving them new ideas on how this disease is working.
They are also learning what type of management would be acceptable to people, and while hunters and non-hunters have different ideas, people are more likely to support lethal removal of elk with hoof disease only in situations where a lot of animals were affected and not when only a few are infected, she said.
"What I would like for you to keep in mind is from a disease management standpoint, the only time we have a chance of managing a disease is if we hit it hard and hit it fast early on," Wild said.