(Observations from 2012 to present.)
Limping = Red, Dead = Black
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Observations of elk with deformed, broken, or missing hooves have increased dramatically in southwest Washington over the past decade. Tests conducted by scientists in the U.S. and abroad show these abnormalities are strongly associated with treponeme bacteria, known to cause digital dermatitis in cattle, sheep and goats.
Digital dermatitis has plagued the livestock industry for decades, but the disease has never before been documented in elk or other wildlife. The Washington Department of Fish and Wildlife (WDFW) is working with scientists, veterinarians, outdoor organizations and others to develop management strategies for elk herds affected by the disease.
Several aspects of the disease in elk are clear:
- Treponeme associated hoof disease appears to be highly infectious among elk, but there is no evidence that it affects humans.
- Tests show the disease is limited to animals’ hooves, and does not affect their meat or organs.
- Currently, there is no vaccine for the disease, and there are no proven options for treating it in the field.
Scientists believe that treponeme bacteria likely persist in moist soil and spread to new areas on the hooves of infected elk. To help minimize the spread of the disease, WDFW requires hunters to remove the hooves of any elk taken in affected areas and leave them on site. During the 2015-16 hunting season, this rule applied to Game Management Units 501-564 and 642-699 in southwest Washington.
In 2013, WDFW created two advisory groups to help address scientific issues and societal concerns raised by the disease. The Hoof Disease Technical Advisory Group helped to guide the diagnostic effort and members continue to consult with the department on evolving research needs. The Hoof Disease Public Working Group consults with WDFW on management issues and helps to publicize information about the disease.
Both groups collaborate with the department on field studies to assess the distribution, prevalence, and other dynamics of the disease.
Sightings of limping elk increase
In the late 1990s, WDFW began receiving sporadic reports of limping elk and elk with hoof deformities in the Cowlitz River Basin. Since 2008, sightings have increased rapidly and spread to 10 counties in southwest Washington, affecting both the Mount St. Helens and Willapa Hills elk herds.
The disease is now suspected in Clark, Cowlitz, Grays Harbor, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, and Wahkiakum counties. In 2015, five elk sampled in northwest Oregon tested positive for the treponeme bacteria associated with hoof disease.
In late 2015, evidence of treponeme-associated hoof disease was detected in an abnormal hoof taken from an elk killed in Skagit County and submitted for testing by WDFW. Additional testing is planned in early 2016 to determine whether the bacteria are the same as those found in southwest Washington.
Diagnosing hoof disease in elk
Starting in 2009, WDFW collected hooves and tissue from 43 elk and sent samples to five laboratories for independent analyses. The elk were selected by age and sex, and taken from areas known to be affected by hoof disease as well as those believed to be free of the disease. By 2014, the treponeme bacteria had been independently identified in samples from affected elk in each laboratory, providing evidence of their role in causing the disease.
Those tests supported the findings of WDFW’s Technical Advisory Group, which agreed that the disease most closely resembles a form digital dermatitis that afflicts domestic sheep. WDFW continues to work with researchers, epidemiologists, veterinarians and diagnostic labs around the world to learn more about the disease.
Digital dermatitis in livestock
First reported in Italy in 1974, digital dermatitis is a hoof disease known to cause lameness in cattle, sheep, and goats. Multiple bacteria likely play a role in the disease, but treponeme bacteria are most apparent.
Bovine digital dermatitis, which emerged as a serious disease of dairy cattle in the United States in the 1990s, is now the leading cause of lameness in dairy cows nationwide. It has been found to occur in 70 percent of the nation’s dairies and is responsible for 50 percent of all cases of lameness in cows. Contagious ovine digital dermatitis in sheep has never been diagnosed in the U.S. but is increasingly being documented in the United Kingdom and Ireland.
The condition of infected livestock may improve if their hooves are trimmed and they receive repeated applications of topical antibiotics and daily footbaths. However, they frequently become re-infected after treatment, and wildlife managers do not believe this approach is feasible for treating free-ranging elk.
Field studies and other actions
Treponeme-associated hoof disease presents a significant challenge for elk management in Washington State. In 2015, WDFW conducted two field studies to learn more about the scope and impact of the disease. Following those studies, the department established criteria for euthanizing individual elk that are severely afflicted.
- Survival and reproduction: As of January 2016, wildlife managers had radio-collared 94 cow elk in the Mount St. Helens area. These elk will be monitored during the next four years to understand the possible effects of the disease on elk survival and reproduction.
- Prevalence: In the spring of 2015, a team of 223 volunteers drove more than 7,000 miles across 10 counties to help assess the proportion of elk affected by the disease. Volunteers and WDFW staff documented over 250 observations of groups of elk during the citizen-science effort.
- Euthanasia protocol: In consultation with its working and advisory groups, WDFW determined that culling elk is not likely to effectively control the spread of hoof disease. The department did, however, approve a euthanasia protocol designed to end the suffering of individual animals.
WDFW continues to encourage the public to report observations of elk with hoof deformities on the reporting web tool on this page.
Back ground information information (Merck Veterinary Manual):