PULLMAN, WA — A debilitating hoof disease affecting elk herds across the Pacific Northwest appears to be driven not by a single pathogen but by multiple bacterial species working together, according to a study led by researchers in Washington State University’s College of Veterinary Medicine.
Examining elk hoof tissue, researchers confirmed a previously discovered link between treponeme-associated hoof disease (TAHD) and Treponema spirochete bacteria, while also identifying a second bacterial group, Mycoplasma, as strongly associated with the lesions for which the disease is known. Several additional bacterial groups were found to be associated with TAHD lesions, further suggesting the disease involves multiple microbes rather than a single cause. The findings were published in the journal Applied and Environmental Microbiology.
“What really stood out to us was that similar bacteria were detected in all the regions with TAHD that we looked at, from areas where TAHD is frequently detected to places where cases are more sporadic,” said Liz Goldsmith, lead author of the study. “The consistent presence of Treponema and Mycoplasma in TAHD lesions suggests these bacteria may be working together, and that the disease is driven by a complex microbial community rather than a single pathogen.”
The consistent presence of Treponema and Mycoplasma in TAHD lesions suggests these bacteria may be working together, and that the disease is driven by a complex microbial community rather than a single pathogen.
Liz Goldsmith, graduate research assistant
Washington State University
WSU has been leading the effort to identify the cause of elk hoof disease and to provide critical information to wildlife agencies to better manage the disease in the wild.
TAHD causes painful, ulcerative lesions on elk hooves, leading to lameness and reduced mobility. Although the disease itself is not fatal, affected elk have higher mortality rates, as they can be more vulnerable to starvation, predators, hunters, weather and secondary infections. Currently, there is no vaccine to prevent the disease or proven treatment options for elk in the wild.
The disease was first noted in southwestern Washington elk herds in the late 1990s and has since spread further in the Evergreen State and into Oregon, Idaho and California.
To better understand the cause of the disease, researchers examined hoof tissue samples from 129 free-ranging elk collected from regions where TAHD is widespread, occurs sporadically or has not been detected. Both Treponema and Mycoplasma were found consistently in diseased hoof tissue and were absent from healthy hooves, suggesting they may work together to drive the disease. Several additional types of bacteria were also associated with lesions, including Fusobacterium and a group of Corynebacterium, an indication that TAHD is caused by a complex community of microbes rather than a single pathogen.
“Having a better description of the bacteria that are associated can really help us start to pin down what’s going on with this particular disease,” Goldsmith said, adding that the information also could aid in the development of new diagnostic tools, including tests to detect the disease in live elk rather than only after death as is currently the case.
The team also investigated whether bacterial communities differed between areas with heavy outbreaks and regions with more sporadic cases. Goldsmith, who recently completed her doctorate in biomedical sciences and an anatomic pathology residency in the College of Veterinary Medicine, said no significant differences were found.
“This was quite the surprise,” she said. “It seemed reasonable to think that variation in bacterial communities might explain why some areas see more hoof disease cases than others, but the bacterial patterns were remarkably consistent.”
Follow-up research is under way to better understand where these bacteria are within lesions and how they might interact. Using tissue analysis techniques, the team has begun pinpointing the location of specific bacteria within lesions, which may reveal how they contribute to tissue damage and disease progression and could contribute to development of improved diagnostic methods.
