Wild horses have potential to stem killer toxins on American rangelands


Most Americans have heard of ebola, anthrax and the Spanish flu, all of which are deadly pathogens and all of which have killed millions of people over the decades.

However, there are some diseases caused by toxins that are not so well-known, yet have capacity to sicken and kill both people and animals in great numbers.

Prions are such a toxin and pose a serious health risk to humans, cervids (deer, elk and moose) and also to livestock, where in cattle, prions manifest as ‘mad-cow’ disease (BSE).

It seems we are currently faced with a new and emerging challenge to our North American deer, elk and moose herds, locally and nationally from such a prion-based disease.

The prion infections in deer, elk and moose (‘cervids’ collectively) is causing Chronic Wasting Disease (‘CWD’); a very serious illness that can kill. And recent experiments with monkeys suggests it may be communicable to humans.

And it may only be a matter of time before it starts moving from cervids and their grazing environments into our livestock, if livestock are commingled with cervids grazing upon infected grasses and brush (suspected prion vectors).

In fact, one of the leading scientific investigators into prion infections wants to start burning grasses to eliminate suspected grass-borne vectors of CWD, according to this N.Y. Times article.

In addition to adversely affecting the $10-billion dollar annual hunting industry in America, CWD and infectious prion diseases certainly have the potential to be devastating to the livestock industry.

Prions are the infectious agent in ‘mad-cow’ disease in cattle, and ‘scrapies’ in sheep.

Prions are misshapen proteins and are particularly worrisome compared to bacteria and viruses because they can be transmitted into animals from contaminated grasses and brush by ingestion, as well as potentially transmitted between animals via contact through other environmental vectors. In the environment, prions can remain infectious for very long periods of time compared to some bacteria and viruses.

The fact that we currently have very little surveillance data (in most geographical areas none!) as to the scope and level of infection already present in America and its cervid herds, makes the problem quite serious.

Dr Mark Zabel
Dr Mark Zabel

In fact, according to Colorado State University’s Dr. Mark Zabel, who was kind enough to spend a couple hours on the phone with me over the past week, there is very little data on which locations across America may be CWD enzoonitc areas.

We really have no idea as to what extent CWD is present in local and west coast cervids and in the grazing environments in and around our forests. And there are already deer and elk that arguably show symptoms of CWD around the western states.

As I have learned from Dr. Zabel, the symptoms of prion disease can easily be mistaken for other causes, such as selenium deficiency. And given the complexity of the diagnoses and limited laboratory facilities able to make such diagnoses, prion diseases can be easily overlooked, allowing it to potentially extend into other animal populations.

According to a Scientific American article, misdiagnoses of prion-involved disease in humans may be more widespread than believed:

“In the human form of mad cow disease, called Creutzfeldt-Jakob, a person’s brain deteriorates — literally developing holes that cause rapidly progressing dementia. The condition is fatal within one year in 90 percent of cases. The culprits behind the disease are prions — misfolded proteins that can induce normal proteins around them to also misfold and accumulate. Scientists have known that these self-propagating, pathological proteins cause some rare brain disorders, such as kuru in Papua New Guinea. But growing evidence suggests that prions are at play in many, if not all, neurodegenerative disorders, including Alzheimer’s, Huntington’s and Parkinson’s, also marked by aggregations of malformed proteins.”

Recently, an article published in USA Today’s Wisconsin Farmer discussed another concerning study about prions and CWD:

“Three of five macaques that were fed infected white-tailed deer meat over a three-year period tested positive for CWD.

“The meat fed to the macaques represented the human equivalent of eating a seven-ounce steak per month.”

It is quite important to note that among large North American herbivores, wild horses (an American native species: click here) are uniquely immune to prions, arguably so through some evolutionary process, which we do not yet understand.

And by abating grasses and brush (each horse consuming 30lbs. of dry grass and brush daily) one of the suspected vectors, wild horses can meaningfully reduce environmental prions affecting other grazing animals, including cervids. This is important because the rate of infection for this prion disease (CWD) is believe to be dose-related. Such grazing by wild horses also has the added benefit of reducing the fuels (grass and brush) for catastrophic wildfires as I discuss in this article.

As we consider all of the foregoing, in light of the BLM’s notion of removing even more wild horses from public lands to increase and extend grazing areas for cattle and sheep into known grazing areas where cervids are present, such a move is clearly a “bad idea” according to Dr. Zabel.

Grazing livestock in proximity to cervids may subject cattle and sheep to prion infections, which may initially be very difficult to perceive or diagnose short of a laboratory analyses, and potentially thereafter, infecting humans who have ingested the meat of any infected animals.

However, I defer to Dr. Mark Zabel, one of the world’s leading experts on the subject, who addressed that concern in the message below where I posit the question to about co-mingling cattle and sheep in areas grazed by cervids:

—–Original Message—–

From: Capt. William E. Simpson – USMM
To: Zabel, Mark
Sent: Thu, Jul 12, 2017 21:16

I think we should have a discussion about how involved you and/or your team would like to be in studying a deployment of wild horses into an ecosystem alongside cervids. And if so, it may be important to survey the existing animals in the area(s) before the horses are deployed in developing some baseline data.

You’re the expert so you’ll have to tell me, but it seems logical that there may be some vector/biological path from the prions causing CWD in cervids to potentially infect livestock via some form of transmission, possibly from cattle and sheep being on grazing lands and sharing water sources with infected cervids? The cattle industry cannot afford any further BSE or similar out breaks (one sick cow with ‘mad-cow shuts the industry down), and they are pushing the US Forest Service hard to graze more cattle in immediate proximity to cervids, sharing grazing and water sources. I think that may be unwise until completed surveys have been conducted and pathways for transmission have been fully explored.

From my relatively ignorant perspective on potential transmission paths, it seems reasonable to think that the cattle/sheep industry would;

1. Want to avoid grazing cattle and sheep in close proximity to cervids, at least or until cervid populations could be surveyed for prions and rates of infection; and,

2. Begin the study of equids and cervids co-existing in an ecosystem to determine what aspect of the evolutionary mutualism has and may continue to benefit cervids through equid mutualism, and possibly determine what mechanism led to the horse’s acquired an immunity to the prions … and if there is a potential cure that can be applied; gene therapy …  epigenetic path to resistance?

The USFS, BLM and the Cattle industry might be inclined to help fund such surveys and studies for the obvious reasons …

From: Zabel, Mark 
To: Capt. William E. Simpson – USMM
Sent: Thu, Jul 13, 2017 11:48 am

You are absolutely right and I would strongly discourage any cattle from grazing in CWD endemic areas. Really short-sighted and bad idea until we know further how prions jump species barriers. Cattle ranchers would not like the bad publicity if the media and beef consumers found out that cattle are mingling with cervids, especially in confirmed CWD enzoonitc areas.

Majestic, one of the wild stallions of Wildhorse Ranch.

Now that there are fewer than 50,000 wild horses ranging-free in America and with Sec. Zinke looking at killing the balance of all the remaining wild horses at the BLM corrals (about 40,000), we seem to be facing a very serious time-sensitive issue where the BLM (Sec. Zinke) is considering slaughtering (soon) the only known cost-effective solution to a potential problem with a national scope; this emerging prion problem.

So what happens if Secretary Zinke allows slaughter of the only animals (wild horses) which can effectively abate the prion vectors in the wilderness and forest lands of the BLM and USFS? Who knows? But on its face, I think it has disaster written all-over it. It reminds me of a forester who told me that ‘BLM’ stands for Bureau of Large Mistakes.

Killing the only potential natural and readily available solution to a couple of very serious emerging problems seems like the ‘bad idea’ of all time to me!

Let’s examine the benefits of harnessing the natural abilities of wild horses to once again serve mankind by using them instead of killing them:

  1. BLM saves about $50m/annually in costs related to keeping the 40,000 horses corralled; and,
  2. Mitigated wildfire fuels saves insurance industry hundreds of millions annually in losses as a small fraction of their current multi-billion dollar losses; and,
  3. Less fire means less fire suppression costs to the USFS (USFS spends 1/2 of its budget on fires), and savings to USFS and BLM-DOI translates to taxpayer savings; and,
  4. Grass and brush abatement by wild horses (immune to prions) may alter prion disease vectors (grasses and brush) and introduction into game animals (deer, elk, moose) that are now succumbing to the prion-caused chronic wasting disease (CWD), which is good for hunting lobbies ($10b annually). Having the immune wild horses abate excess grasses and brush may also provide some fire-walling against transmission of emerging prion diseases into domestic livestock herds from deer and elk (mad-cow – livestock lobby) and potentially infecting humans (medical community). Releasing wild horses back into the wilderness and creating a pilot program to study their affect on CWD may lead to some insights and methodologies for protecting livestock; and,
  5. Last but not least, Wild Horses and Burros provide highly beneficial symbiotic mutualisms to all of their historical ecosystems and add to the aesthetics and tradition of the American wilderness. This final statement is consistent with the Congressional preamble to the 1971 Wild Burro and Horse Protection Act. 
Wild horses in the Pryor Mountains.
Wild horses in the Pryor Mountains. © Jana Wilson/BLM


(PUBLIC LAW 92-195)  §1331. Congressional findings and declaration of policy

“Congress finds and declares that wild free-roaming horses and burros are living symbols of the  historic and pioneer spirit of the West; that they contribute to the diversity of life forms within the Nation and enrich the lives of the American people; and that these horses and burros are fast disappearing from the American scene. It is the policy of Congress that wild free-roaming horses and burros shall be protected from capture, branding, harassment, or death; and to accomplish this they are to be considered in the area where presently found, as an integral part of the natural system of the public lands.”

Concerned readers should write, email and call their local representatives, state representative and especially DOI Sec. Zinke and AG Sec. Sonny Purdue, and weigh in on the pending decision to slaughter the relatively few remaining wild horses.

Horses have served mankind over the millennia and are a gift from our Creator.

God’s law, which is above man’s law, and which is codified in the Bible clearly states that eating horses is forbidden, according to Leviticus-11 and Deuteronomy-14.

Eating horses or burros is also forbidden under all other Mosaic Law.

Is it too much to ask that our own government and its agencies do what’s right for everyone for a change?


William E. Simpson

William Simpson is the author of Dark Stallions - Legend of the Centaurians, proceeds from which go towards supporting wild and domestic horse rescue and sanctuary. » Read Bill's profile

12 thoughts on “Wild horses have potential to stem killer toxins on American rangelands

  • July 16, 2017 at 12:02 pm

    Leave our horses free and alone. We will fight for our horses.

  • July 20, 2017 at 7:41 am

    Thank you again for a very well written case for the necessary existence of our equine roaming free on their native land. I would be suspicious of the intent of the cattle industry. When they feel a threat to their bottom line they could call for free the wildlife services contractor and have the deer, elk, etc exterminated without any testing. Which they have done in the past. If publicized some excuse in talking points to placate the public will than be sent out. Sorry, for my attitude – please keep up your articles and well thoughtful study. Thank you again Mary

  • July 22, 2017 at 5:44 am

    Bovine Spongiform Encephalopathy has resulted from ranchers grinding up dead cattle and feeding their remains to live ones. If a human being eats beef, he is in danger of developing it, too; the prions can not be cooked out of it. Let the horses run free and eat their native foods while they nourish the soil with their uncontaminated droppings. Horses don’t eat meat.

  • August 28, 2017 at 8:37 am

    We have 5 days left before Congress come back and make a ruling on the Wild Mustang , to kill them by shooting them or send them all to Slaughter . It is up to all of Us to be a POWERFUL VOICE For the Wild Mustangs , They Have a Right to Live on their range Wild and Free. Please Call your Senator and tell them that you are against this proposal that the Senate is going to Rule On .. THe Wild Mustang Need our Help our Voice to Speak for Them . I Opposed Slaughter and the removal of the Wild Mustang and Burros from the RANGE > they have rights to Roam Free on the lands they were born on. Wild Freedom Federation

  • October 19, 2017 at 3:51 pm

    Please site the studies used to determine any immunity wild horses have to prions. And also, how many horses it would take to eat affected forage or enough of it to erradicate this disease? It seems to me that having made a jump to monkeys, leading to a likelihood of manifesting itself as other disease diagnosis in humans, it would make sense that we may very well see it in horses over time. There has not, to my knowledge, been any studies proving wild horse immunity. I really don’t want them unnecessarily exposed, or experimented on to find out.

  • October 23, 2017 at 5:15 pm

    Here’s a thought: Stop eating meat. It’s healthier for people, and it’s better for the environment. No overgrazing by livestock means more forage for wild horses. No horses in government holding, no tax subsidies for ranchers, no tax dollars to eradicate predators or round up up horses, means massive savings of our tax dollars, and healthier ranges. What a concept!

  • December 25, 2018 at 5:12 pm

    I call BS. Here from REAL studies –

    “An infectious brain disease that has been killing deer, elk and moose both in the wild and on “captive farms” continues to stalk the land, expanding its domain to 23 states and two Canadian provinces since it was first identified in captive mule deer in a Colorado research facility in 1967.”

    “As for CWD and any risks to humans, the alliance says there is currently no solid evidence that humans can get it from deer, elk or moose. Most researchers agree with that. According to the group, the diseases (BSE(Mad Cow disease) and CWD) are “distinctly different.”

    “Dunfee added that Wyoming did a 13-year study in which cows were put in deer pens heavily infected with CWD, and none of the cows became infected.”

  • December 26, 2018 at 11:51 am


    Cervid to human prion transmission

    Kong, Qingzhong

    Case Western Reserve University, Cleveland, OH, United States


    We hypothesize that:

    (1) The classic CWD prion strain can infect humans at low levels in the brain and peripheral lymphoid tissues;

    (2) The cervid-to-human transmission barrier is dependent on the cervid prion strain and influenced by the host (human) prion protein (PrP) primary sequence;

    (3) Reliable essays can be established to detect CWD infection in humans; and

    (4) CWD transmission to humans has already occurred. We will test these hypotheses in 4 Aims using transgenic (Tg) mouse models and complementary in vitro approaches.



    Scrapie, CWD, tse prion, transmit to pigs by oral route

    ***> However, at 51 months of incubation or greater, 5 animals were positive by one or more diagnostic methods. Furthermore, positive bioassay results were obtained from all inoculated groups (oral and intracranial; market weight and end of study) suggesting that swine are potential hosts for the agent of scrapie. *** Although the current U.S. feed ban is based on keeping tissues from TSE infected cattle from contaminating animal feed, swine rations in the U.S. could contain animal derived components including materials from scrapie infected sheep and goats. These results indicating the susceptibility of pigs to sheep scrapie, coupled with the limitations of the current feed ban, indicates that a revision of the feed ban may be necessary to protect swine production and potentially human health. Results: PrPSc was not detected by EIA and IHC in any RPLNs. All tonsils and MLNs were negative by IHC, though the MLN from one pig in the oral <6 month group was positive by EIA. PrPSc was detected by QuIC in at least one of the lymphoid tissues examined in 5/6 pigs in the intracranial 6 months group, 5/6 pigs in the oral 6 months group. Overall, the MLN was positive in 14/19 (74%) of samples examined, the RPLN in 8/18 (44%), and the tonsil in 10/25 (40%).

    ***> Conclusions: This study demonstrates that PrPSc accumulates in lymphoid tissues from pigs challenged intracranially or orally with the CWD agent, and can be detected as early as 4 months after challenge. CWD-infected pigs rarely develop clinical disease and if they do, they do so after a long incubation period.

    This raises the possibility that CWD-infected pigs could shed prions into their environment long before they develop clinical disease.

    Furthermore, lymphoid tissues from CWD-infected pigs could present a potential source of CWD infectivity in the animal and human food chains.





    Cervid to human prion transmission 5R01NS088604-04 Update

    National Institute of Health (NIH)


  • December 26, 2018 at 11:52 am

    FRIDAY, DECEMBER 14, 2018

    Norway, Nordfjella VKM 2018 16 Factors that can contribute to spread of CWD TSE Prion UPDATE December 14, 2018



    THURSDAY, OCTOBER 25, 2018

    ***> Norway New additional requirements for imports of hay and straw for animal feed from countries outside the EEA due to CWD TSE Prion



  • December 26, 2018 at 11:53 am


    here is the latest;


    Oral transmission of CWD into Cynomolgus macaques: signs of atypical disease, prion conversion and infectivity in macaques and bio-assayed transgenic mice

    Hermann M. Schatzl, Samia Hannaoui, Yo-Ching Cheng, Sabine Gilch (Calgary Prion Research Unit, University of Calgary, Calgary, Canada) Michael Beekes (RKI Berlin), Walter Schulz-Schaeffer (University of Homburg/Saar, Germany), Christiane Stahl-Hennig (German Primate Center) & Stefanie Czub (CFIA Lethbridge). To date, BSE is the only example of interspecies transmission of an animal prion disease into humans. The potential zoonotic transmission of CWD is an alarming issue and was addressed by many groups using a variety of in vitro and in vivo experimental systems. Evidence from these studies indicated a substantial, if not absolute, species barrier, aligning with the absence of epidemiological evidence suggesting transmission into humans. Studies in non-human primates were not conclusive so far, with oral transmission into new-world monkeys and no transmission into old-world monkeys. Our consortium has challenged 18 Cynomolgus macaques with characterized CWD material, focusing on oral transmission with muscle tissue. Some macaques have orally received a total of 5 kg of muscle material over a period of 2 years.

    After 5-7 years of incubation time some animals showed clinical symptoms indicative of prion disease, and prion neuropathology and PrPSc deposition were detected in spinal cord and brain of some euthanized animals. PrPSc in immunoblot was weakly detected in some spinal cord materials and various tissues tested positive in RT-QuIC, including lymph node and spleen homogenates. To prove prion infectivity in the macaque tissues, we have intracerebrally inoculated 2 lines of transgenic mice, expressing either elk or human PrP. At least 3 TgElk mice, receiving tissues from 2 different macaques, showed clinical signs of a progressive prion disease and brains were positive in immunoblot and RT-QuIC. Tissues (brain, spinal cord and spleen) from these and pre-clinical mice are currently tested using various read-outs and by second passage in mice. Transgenic mice expressing human PrP were so far negative for clear clinical prion disease (some mice >300 days p.i.). In parallel, the same macaque materials are inoculated into bank voles.

    Taken together, there is strong evidence of transmissibility of CWD orally into macaques and from macaque tissues into transgenic mouse models, although with an incomplete attack rate.

    The clinical and pathological presentation in macaques was mostly atypical, with a strong emphasis on spinal cord pathology.

    Our ongoing studies will show whether the transmission of CWD into macaques and passage in transgenic mice represents a form of non-adaptive prion amplification, and whether macaque-adapted prions have the potential to infect mice expressing human PrP.

    The notion that CWD can be transmitted orally into both new-world and old-world non-human primates asks for a careful reevaluation of the zoonotic risk of CWD..

    ***> The notion that CWD can be transmitted orally into both new-world and old-world non-human primates asks for a careful reevaluation of the zoonotic risk of CWD. <***



    P190 Human prion disease mortality rates by occurrence of chronic wasting disease in freeranging cervids, United States

    Abrams JY (1), Maddox RA (1), Schonberger LB (1), Person MK (1), Appleby BS (2), Belay ED (1) (1) Centers for Disease Control and Prevention (CDC), National Center for Emerging and Zoonotic Infectious Diseases, Atlanta, GA, USA (2) Case Western Reserve University, National Prion Disease Pathology Surveillance Center (NPDPSC), Cleveland, OH, USA..

    SEEMS THAT THEY FOUND Highly endemic states had a higher rate of prion disease mortality compared to non-CWD states.


    P172 Peripheral Neuropathy in Patients with Prion Disease

    Wang H(1), Cohen M(1), Appleby BS(1,2) (1) University Hospitals Cleveland Medical Center, Cleveland, Ohio (2) National Prion Disease Pathology Surveillance Center, Cleveland, Ohio..

    IN THIS STUDY, THERE WERE autopsy-proven prion cases from the National Prion Disease Pathology Surveillance Center that were diagnosed between September 2016 to March 2017,


    included 104 patients. SEEMS THEY FOUND THAT The most common sCJD subtype was MV1-2 (30%), followed by MM1-2 (20%),


    THAT The Majority of cases were male (60%), AND half of them had exposure to wild game.

    snip…see more on Prion 2017 Macaque study from Prion 2017 Conference and other updated science on cwd tse prion zoonosis below…terry



  • February 27, 2019 at 11:16 pm

    Based on my observation over the last 5 months and the research that I have done, I am concerned that this may be Contagious Wasting Disease. There has been 1 fatality thus far within the herd. Horses as well as cattle share a fence with the Elk; although there have not been any (Wyoming) reports of CWD in horses and/or cattle ((that I have found)), I am not convinced that it couldn’t. I think that it may be a possibility and I’m worried about the welfare of my own horses (I own adjacent property) as well as the well being of the Elk, Cattle, and Horses. Please contact me by landline at 907-745-2445, cell phone 307-231-3708, and/or email aliciahallalaska@gmail.com

    Thank you.

    Best Regards,
    Alicia Hall
    Wolverine Equestrian Park, Alaska

    P.S. I do not know the cause of death of the one elk that died about 5 months ago but that is when I started watching this slightly thinner elk and have to my best effort documented via dated photos of his progression; showing signs of lethargy, isolation, lack of appetite, abnormal/unresponsive behavior, and most recently diarrhea. Also there is a very sad glazed look in its eyes. … There may also be a welfare concern as the owners have taken no action allowing the suffering to go beyond what I would consider humane.
    This is not a report of animal abuse or neglect but rather a concern for the well-being of these and other animals.

  • February 28, 2019 at 8:35 am

    Alicia Hall, you have great cause to be very cause.

    1st, this statement is absolutely incorrect;

    ”Wild horses’ immunity to prions – the toxins causing Chronic Wasting Disease – gives them a unique place on the range lands.”

    they have no clue, and no transmission studies have been done…but;

    The first report of polymorphisms and genetic characteristics of the prion protein gene (PRNP) in horses
    Yong-Chan Kim ORCID Icon & Byung-Hoon Jeong ORCID Icon
    Pages 245-252 | Received 07 May 2018, Accepted 07 Aug 2018, Accepted author version posted online: 30 Aug



    new outbreak of TSE Prion in NEW LIVESTOCK SPECIES

    mad camel disease




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