Mr. Gosch:
I’m writing in response to your July 9, 2014 email where you shared your concerns about the safety of consuming meat from elk afflicted with treponeme-associated bacterial hoof disease.
The concerns and questions you have raised with the Washington Department of Fish and Wildlife (WDFW) fall into the four categories below, which I will respond to in the following order:
1. Questions about our diagnosis of treponeme-associated bacterial hoof disease.
2. Safety of consuming meat from “sick” vs. “severely crippled” elk.
3. Concern that elk meat may be contaminated by the herbicide atrazine, thus posing a risk to humans who consume the meat.
4. Concern that elk may be infected with Leptospira sp. bacteria, thus posing a risk to humans who handle elk or their carcasses.
Diagnosis of treponeme-associated bacterial hoof disease of elk
Biologists and veterinarians are professionally obligated to adhere to a scientifically acceptable process in the design of their research question(s) or diagnostic investigation, and in interpreting the results. This process includes a review of the existing scientific literature; development of the research question(s) or list of differential diagnoses; selection and use of appropriate methods and tests; sound interpretation of results; and submission of findings to the scientific community for peer review.
Peer review is a critical component of the scientific process, involving presentations at professional association conferences, publication in scientific journals, and dissemination of new information to colleagues and eventually to the public. WDFW’s veterinary staff will be presenting the findings of our elk hoof disease investigations at three upcoming animal disease conferences. Manuscripts describing elk hoof disease in SW Washington and evidence for treponemes being causal are currently in preparation by several of our collaborators. These will go through the peer review process and will be published in reputable scientific journals. Finally, information on treponeme-associated bacterial hoof disease in elk is being disseminated through appropriate channels, such as the July 3 edition of the Washington State Veterinary Medical Association online newsletter:
http://wsvma.org/2014/07/03/severe-treponeme-associated-bacterial-hoof-disease-in-southwest-washington-elk/ As you know, WDFW has relied on the expertise of our 16-member technical advisory group (TAG) to help guide our diagnostic investigation and to assess the results of that effort. Our TAG includes researchers and veterinarians with expertise in clinical veterinary medicine, epidemiology, pathology, microbiology, toxicology, public health, food animal production, and wildlife health. A list of TAG members can be found here:
http://wdfw.wa.gov/about/advisory/ehdtag/EHDTAG_MemberRoster.pdf. Based on all evidence available to date, the TAG developed the following three consensus statements at its June 3, 2014 meeting:
· Available evidence is most consistent with an infectious bacterial hoof disease.
· The disease shares many features and most resembles treponeme-associated contagious ovine digital dermatitis (CODD).
· Environmental factors, including wet conditions, are likely important in disease initiation and propagation
In your letter, you list several statements attributed to members of the TAG at this meeting. You indicate that these statements may refute the above consensus statements, or the diagnosis of treponeme-associated bacterial hoof disease. Without the context in which these statements were made, it is difficult to discern their meaning or significance. However, I am aware of the tendency of scientists – when in the same room together and probing the extent of current understanding of a particular issue – to do a lot of brainstorming, looking at a problem from a variety of angles, and thinking out loud. This casual process and mild debate can be viewed as an informal version of peer review, and also an important initial step in defining additional research questions and developing testable hypotheses.
When the statements you provided were shared with the TAG, one member said this: “Scientists tend to try on and discard ideas, often out loud, which can get very confusing to the public.” Another said: “Unfortunately, given the public nature of the discussions, I don't know how you can avoid laypeople from over-interpreting one small portion of the discussion (or several small portions for that matter) and not even understanding other portions of the discussion.”
In any case, the TAG reached consensus that the preponderance of evidence points to treponeme-associated bacterial hoof disease. That conclusion is consistent with field and laboratory evidence in affected elk, as well as what is reported in the scientific and veterinary literature.
You correctly note that this is a complex disease, probably involving species of bacteria in addition to treponemes – as is known to be the case with similar diseases in livestock: bovine digital dermatitis (BDD) of cattle and CODD of sheep. I encourage you to contact our agency veterinarian, Dr. Kristin Mansfield, who can provide you with more information on treponeme-associated bacterial hoof diseases, or direct you to the existing large body of scientific literature on this subject.
Safety of consuming meat from “sick” vs. “severely crippled” elk
In your letter, you suggest that WDFW is giving conflicting advice with respect to the safety of meat from “sick” animals vs. “severely crippled” animals. It is true that the definition of “sick” can be arbitrary and subjective, and may mean different things to different people. Still, we believe that most people – particularly hunters – are capable of recognizing an obviously sick animal. Obvious signs of “sickness” include animals exhibiting extreme lethargy and/or depression; extreme emaciation; lack of awareness or fear of humans or predators; disinterest in their surroundings; unwillingness or inability to stand; labored breathing or coughing; discharge from the eyes, nose, or mouth; or evidence of diarrhea. We would recommend against eating the meat of an animal exhibiting these clinical signs, regardless of the condition of its hooves.
Conversely, if a disease or other abnormality is localized to the hoof, there is no reason to believe that the meat of that animal is unsafe for human consumption as long as the animal appears otherwise healthy. Domestic cattle and sheep with similar treponeme-associated bacterial hoof diseases are routinely sent to slaughter for human consumption. In southwest Washington, several thousand elk – including those with treponeme-associated bacterial hoof disease – are harvested, and their meat consumed, every year. Yet, neither WDFW nor the Washington State Department of Health has received reports of any human disease associated with consumption of elk with treponeme-associated bacterial hoof disease.
Herbicides
The diagnosis of treponeme-associated bacterial hoof disease is congruent with the existing body of scientific and veterinary knowledge, examination and laboratory testing of affected elk in SW Washington, and current expert opinion. In contrast, there is no scientific evidence to suggest that treponeme-associated bacterial hoof disease is caused by herbicides.
Additionally, you raised concerns that hunters are eating elk meat contaminated by herbicides, and you cited an Iranian journal article where the authors detected atrazine in the blood and urine of cattle that were fed corn-based silage. We know that atrazine is one of the most commonly used herbicides for growing corn, including in the United States, and that most livestock feed in this country is corn-based. Yet eating the meat and drinking the milk from domestic livestock is not believed to represent a threat to the health of Americans who consume these animal products. The mere fact that a substance can be detected in an animal’s system does not mean that it is having an effect on its health, or those that consume the animal.
Leptospirosis
It has been known for several decades that wildlife in Washington and throughout the world can be infected with Leptospira sp. bacteria. During the course of WDFW’s hoof disease investigations, evidence of the presence of Leptospira sp. bacteria was found in individual elk with and without hoof disease, and in areas of the state with and without hoof disease (i.e., low titers indicating animals were not having active disease). These findings were not surprising. According to Dr. Jennifer Wilson-Welder, research microbiologist and leptospirosis expert at U.S. Department of Agriculture National Animal Disease Center: “Several strains of leptospirosis are endemic in wild and domestic animals throughout the world, including Washington. In endemic hosts, such as deer, elk, cattle, rodents, raccoons, and other wildlife, the disease is limited to the kidney, urinary and reproductive tracts. Muscle and joint pain reported by humans and other susceptible animals, such as dogs or horses, with leptospirosis is due to severe systemic sepsis and a generalized fever response. Systemic sepsis is not a feature of the disease in endemic animal hosts, and has not been observed in any Washington elk examined to date. Leptospirosis does not affect the hooves of animals; and lameness has not been reported as a feature of clinical leptospirosis in farmed New Zealand red deer, a species closely related to North American elk. Proper diagnostic tests have been applied to samples collected from elk, and positive results were found in both non-hoof diseased animals/areas as well as the ones with hoof lesions. Lack of similarity of clinical signs and failure to find Leptospira titers isolated to only the hoof-diseased animals indicate to the veterinary and research team that leptospirosis is not a cause of the hoof-disease."
Additional information on wildlife diseases that hunters should be aware of can be found at this link:
https://www.avma.org/public/Health/Pages/Disease-Precautions-for-Hunters.aspx ; and information on safe game meat handling and consumption can be found here:
http://wdfw.wa.gov/hunting/meat_safety/ I hope that you find this information useful.
Nate
