Bighorn Sheep from Two Herds are Sick and Dying Due to Disease Spread by Domestic Sheep

Guest opinion by Melissa Cain, Bighorn Conservation Director for Western Watersheds Project

Photo by Erik Molvar/WWP

Last week, wild bighorn sheep herds in Washington and Oregon have been detected with deadly pneumonia, likely caused by a deadly pathogen spread by domestic sheep grazing on public lands. The bighorn are dying slow and painful deaths because they have no natural immunity to the livestock-borne disease.

In Washington, the Department of Fish and Wildlife announced that deadly pneumonia had been detected in the Cleman Mountain herd of bighorn sheep, located primarily in the Okanogan-Wenatchee National Forest northwest of Yakima. A day later, the Oregon Department of Fish and Wildlife announced the detection of pneumonia in the Burnt River herd, southeast of Baker City. Both herds of bighorn likely contracted the illness from domestic sheep or goats.

The Forest Service has been failing to address the threat that domestic sheep allotments pose to bighorn sheep, making infections all but inevitable.  Bighorn sheep pneumonia is caused by pathogens carried by domestic sheep and goats, who typically remain asymptomatic themselves. The pathogens, which include the primary infectious agent Mycoplasma ovipneumoniae as well as a variety of bacteria that act as secondary agents to make bighorn sheep ill, originally traveled with domestic sheep from the old world to the new. The bacteria reached the American West in the Mid-1800s as enormous bands of domestic sheep were brought to graze lush mountain meadows throughout the region, decimating populations of bighorn sheep, who hadn’t evolved with the bacteria and thus had no natural immunity. Several states saw their bighorn populations extirpated entirely, while others saw them reduced to a fraction of historic numbers. The bighorn deaths have continued for more than a century, reducing the remaining native herds as well as reestablished herds through sudden all-age die-offs and through subsequent annual losses of lambs, who can contract the bacteria from their mothers long after the initial disease event appears to have passed.

Science tells us that domestic sheep need to stay far away from bighorn in order to keep our wildlife safe – i.e. social distancing for the Bovidae. But the Forest Service is going to need to start making firm decisions about grazing permits, taking the political heat, and giving priority to native wildlife.






  1. Maggie Frazier Avatar
    Maggie Frazier

    Yet one more common sense reason to buy out all grazing allotments and prevent more eradication of our wildlife! The damage to bighorn sheep? The slaughter of buffalo (because of brucellosis) the slaughter of wolves (killed to protect domestic livestock) the absolute slaughter of how many millions of wild AND domestic animals & birds (Wildlife Services). How long will we allow this decimation of our wild species AND our range lands & forests? All in order to subsidize an industry that does not deserve to BE subsidized! Not even dipping a toe into what the logging industry has accomplished!

  2. James A Bailey Avatar

    In particular, there are 3 related management options for dealing with the bighorn-domestic sheep-disease issue. We hear a lot about (1) moving the domestic sheep, which the FS seldom does. Mostly neglected are (2)develop a larger herd of bighorns that will be more resistant to disease, mostly for genetic reasons; and (3)Strategically improve bighorn habitat to draw bighorns away from domestic sheep. Many (most?) of the FS herds are near lower treeline and the Forest border where domestic sheep and goats are common year-round. Bighorn are habitat specialists, doing best with at least 6 seasonal ranges connected by local migration corridors. They should be a species of conservation concern wherever herds are small and isolated. Their habitat needs must be analyzed with a fine-filter analysis. The course-filter analysis usually employed is inadequate, allowing seasonal ranges, unrecognized by the FS, to become abandoned due to forest-shrub encroachment onto key areas, and then due to loss of “herd memory”. Where are the FS bighorn biologists and why are they silent?

    1. Maggie Avatar

      Perhaps the FS doesnt listen to their biologists anymore than they listen to the rest of us! I have to wonder where our “comments” actually go or if anyone takes the time to read them. It does appear that the livestock producers concerns are the ones that matter.

  3. R.DeMario Avatar

    The ewe that infected the herd on the Okanogan-Wenatchee NF was from a local private property owner, not from the grazing allotment on the national forest. Please fact check.

    1. Maggie Frazier Avatar
      Maggie Frazier

      But – no matter what private owner was responsible – the herd was still infected!

  4. Ida Lupine Avatar
    Ida Lupine

    You can only imagine if it was the other way around, what would happen. 🙁

    1. Maggie Frazier Avatar
      Maggie Frazier

      Oh yeah! Look at the reason given for killing buffalo outside of Yellowstone. Cant take a chance on brucellosis infecting livestock! My question is why arent livestock producers vaccinating against it – rather than slaughtering native wildlife as a preventative? No vaccine?
      I would say the same question applies here!

  5. Beeline Avatar

    Best option is to remove the ‘range maggots’ (euphemism for sheep).

    1. Ida Lupine Avatar
      Ida Lupine

      I feel bad, because the cows and sheep are not to blame; it’s their stubborn owners.

      1. Maggie Frazier Avatar
        Maggie Frazier

        thats true, Ida. But until the owners are prevented from destroying public lands, forests, and our native wildlife & their habitat – what alternative is there other than removing them? These owners should not have access to federal ranges – bottom line. Or if they do – pay the going rate, stop the subsidies, & make them responsible for the damage they do. I read that in some cases, they not only use the water rights on public land but CHARGE the gov. for the water wildlife uses (us, the taxpayers). Pretty good deal, right?

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