New Study Comfirms that Bighorn Sheep Die from Domestic Sheep Diseases

Hells Canyon Bighorn Sheep © Ken Cole
Hells Canyon Bighorn Sheep © Ken Cole

A new study in the Journal of Wildlife Diseases confirms, unequivocally, that the domestic sheep disease Mannheimia haemolytica kills bighorn sheep after the two species co-mingle. This paper has been rumored for the last several months and was cited in the recent Payette National Forest decision to close 60% of sheep grazing allotments on the Forest.

Surely this should end the discussion among reasonable people about whether science supports the notion that domestic sheep and bighorn sheep can co-exsist. They cannot and actions must be taken by Federal and State agencies to make sure that the two species do not overlap on the landscape.

ABSTRACT:   Previous studies demonstrated that bighorn sheep (Ovis canadensis) died of pneumonia when commingled with domestic sheep (Ovis aries) but did not conclusively prove that the responsible pathogens were transmitted from domestic to bighorn sheep. The objective of this study was to determine, unambiguously, whether Mannheimia haemolytica can be transmitted from domestic to bighorn sheep when they commingle. Four isolates of M. haemolytica were obtained from the pharynx of two of four domestic sheep and tagged with a plasmid carrying the genes for green fluorescent protein (GFP) and ampicillin resistance (APR). Four domestic sheep, colonized with the tagged bacteria, were kept about 10 m apart from four bighorn sheep for 1 mo with no clinical signs of pneumonia observed in the bighorn sheep during that period. The domestic and bighorn sheep were then allowed to have fence-line contact for 2 mo. During that period, three bighorn sheep acquired the tagged bacteria from the domestic sheep. At the end of the 2 mo of fence-line contact, the animals were allowed to commingle. All four bighorn sheep died 2 days to 9 days following commingling. The lungs from all four bighorn sheep showed gross and histopathologic lesions characteristic of M. haemolytica pneumonia. Tagged M. haemolytica were isolated from all four bighorn sheep, as confirmed by growth in ampicillin-containing culture medium, PCR-amplification of genes encoding GFP and ApR, and immunofluorescent staining of GFP. These results unequivocally demonstrate transmission of M. haemolytica from domestic to bighorn sheep, resulting in pneumonia and death of bighorn sheep.




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  1. JimT Avatar

    So, will the worm turn, so to speak? Will domestic sheep be culled/killed/harvested (my favorite word) to protect the bighorn? Will range be restricted to prevent contact?

    If bison could read, I would if they could appreciate the tragic irony here. They get killed for merely leaving YP boundaries; will the sheep, as vectors, being given the same treatment? Stay tuned…

    1. Ken Cole Avatar

      Short answer….. No.

    2. Ralph Maughan Avatar

      It doesn’t matter how many scientific studies there are, political power plays a huge role in what veterinarians do, and what doctors do with people.

      Sheep ranchers will keep saying “there is no proof,” and their rancher politicians will say it’s true because we get to say anything and those who disagree better watch out.

      One of the things that bothers me most is the growing tendency for lots of groups to say “the world is flat, so to hell with you and your science.”

      1. JimT Avatar

        Sadly, Ralph, I think you have captured the essence of the wolf wars as well with your last sentence.

      2. Ralph Maughan Avatar


        Will just this morning there is a peer reviewed study from MSU that Montana’s proposed wolf hunt (not on hold) would cut the state’s wolf population in half in just one season.

        Idaho and Montana officials immediately rejected the conclusions.

        To the average citizen, knowledge of the difference between a peer reviewed study and a government or corporation controlled and politically dictated study is not clear.

        “MSU study: Hunt would cut Montana wolf population in half.”

      3. JimT Avatar

        Interesting and true. Besides, what do those academic elites at MSU know when compared to the off the cuff opinions offered at the local grange when it comes to who gets the state’s ear.

        Bottom line…same thing I have been saying all along is true…the ranchers, a significant portion of the elk hunting community, the guide community, and the political powers in the affected states all want the same thing…all wolves dead except for those who have GPS units so they can stay inside Yellowstone

  2. Drew Avatar

    Good work! Science at work. How this is received and used will be interesting to watch. Thanks for this info.

  3. Ryan Avatar

    No shit? Didn’t all know this. Now how to fix it is the question.

  4. Marie Bulgin Avatar
    Marie Bulgin

    I wouldn[t celebrate just yet. Did any of you bother to notice that the report also conclusively showed that there was no transfer of M. h to bighorns kept 10 meters away (only 30 ft) from the domestics.
    When given fence line contact for 2 continual months, 3 bighorns contracted the organsim but showed no signs of sickness.
    So how long do you think bighorns in the wild stay within 30 feet of a domestic sheep? Don Knowles, a researcher at WSU pointed out to the Payette National Forest Supervisor: “These data show that even extended fence line contact of 2 months didn’t lead to disease and death. Disease required co-mingling for a minimum of 48 hours and this was after transmission had already occurred in three of the bighorn sheep. These data leave open the possibility that if left at fence-line contact the bighorn sheep would have developed immunity instead of disease. This is a question for future research. These data show the contact time requirement for transmission and disease is complex and requires extended time periods followed by at least 48 hours of co-mingling.”
    What last winter proved is that bighorns can die in large numbers without the help of domestics. So, the real disease trigger is still a mystery.

    1. Ken Cole Avatar


      It should be made clear that there has been confirmed contact between bighorn and domestic sheep near Sula, Montana where the outbreaks started. In all of the other outbreaks, with the possible exception of those in Utah, there were domestic sheep or goats in close proximity to the bighorn herds which were affected. To say that “[w]hat last winter proved is that bighorns can die in large numbers without the help of domestics” is not supported by the evidence. Because contact was not confirmed in all of the outbreaks you cannot say that it didn’t happen.

      I, unfortunately, have not been able to obtain this study yet so I have not reviewed it. One thing is clear though, domestic sheep diseases kill bighorn sheep. You have been saying for many years that this is not the case and we know your agenda is to protect the woolgrowers from the implications of this type of study.

      I don’t know what you propose as a solution to this problem but it is now unequivocally clear that bighorn sheep and domestic sheep are not compatible with each other. If you are proposing vaccinations for bighorn sheep I don’t see this as a feasible solution. Too little is known about the status of bighorn sheep populations in Idaho and the animals, in many cases, are in very remote areas much of the year. That being said, even the most remote animals are subject to these domestic sheep diseases likely through transmission from dispersing rams and have experienced die offs as a result. Wildlife should not have to be vaccinated just so someone can make a buck off the public dole.

      Federal Public lands are not just the dominion of the livestock industry, they are habitats for wildlife and perform many other functions. When one use causes irreparable harm to another, as is the case with domestic sheep diseases causing the death of bighorn sheep, it simply must be ended. We will not stand by while our bighorn sheep decline into oblivion.

      Stick a fork in it. It’s done. Domestic sheep kill bighorn sheep. They are not compatible.

  5. Marie Bulgin Avatar
    Marie Bulgin

    Ken, we have known for ages that when the animals were confined together, bighorn sheep die. What we didn’t know was how much contact and how close that contact had to be before disease was seen. My point has been and still is, how long and how close do you think a bighorn gets to domestic sheep in the wild. These are animals with herders, guard dogs and herding dogs with them all the time. On the Payette, which is the area I know, there have never been contact between the species during the period that the domestic sheep are on their summer range. BHS have never even been observed by the herders and the camp tenders that are there 24/7. I can’t speak to other places and other ranges, but the disease experienced by the Hells Canyon BHS is not due to contact with domestic sheep belonging to the Payette lease holders.
    And what is “close proximity”? The Reseach says that 30 feet is far enough apart to prevent disease and it takes more than fence line contact to produce disease.
    My proposal is to find out why bighorns are so susceptible to a disease that other ruminant generally throw off if nutrition is adequate and stress levels are minimal. I agree, traditional vaccination isn’t a good answer but there are some interesting procedures in the pipeline that might be helpful in the future.
    And in the meantime, look at taking a groups of bighorns which have been plagued with disease and supplementing their winter nutrition. Nutrition makes a huge difference in the immune competency of domestic sheep and cattle, why wouldn’t it for BHS?

    1. Ken Cole Avatar

      I’ve had the chance to read the study and, in fact, it does not say that it took two days of commingling to produce disease. It says that one of the sheep died within two days of the beginning of commingling portion of the experiment. All four of the sheep, even the one which did not contract M. haemolytica during the fenceline portion of the study died within 9 days of the beginning of the commingling portion of the study. There is no evidence to support the claim that “disease required co-mingling for a minimum of 48 hours”.

      The study even says that:

      “It is conceivable that the bighorn sheep that acquired the tagged M. haemolytica during the fence-line contact would have died even without commingling with the domestic sheep.”

      Furthermore, there is no evidence that “if left at fence-line contact the bighorn sheep would have developed immunity instead of disease”. The study actually states the opposite may be true:

      “This notion is supported by the fact that one bighorn died only 2 days after commingling with the domestic sheep.”

      It’s almost as if you want us to believe that these pathogens just appear out of nowhere like is postulated by the theory of spontaneous generation. These pathogens don’t just live in the dirt and spring forth to cause disease, they must have a host and that host is domestic sheep and goats.

  6. Cody Coyote Avatar
    Cody Coyote

    The Wyoming Game and Fish is reporting that its flagship herd of Bighorns near Dubois, the Whiskey Mountain population , is now also infected with pneumonia.

    Their press releases say nothing about proximity to domestic sheep.

    Perhaps Hoskins has some info on that…

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