Controversy in Idaho Legislature over the threat posed by the meningeal worm to elk, mule deer, and moose

Elk breeders push to relax rules. Legislature close to rejecting the breeders-

White-tailed deer and the parasitic meningeal worm (Parelaphostrongylus tenuis) coexist fairly well. They have fought each other to a near standstill in evolutionary conflict spanning perhaps a million years. The whitetails rarely get sick from these adult nematode type worms that live in the membranes surrounding the brain, called meninges.

The same can’t be said for mule deer, elk, moose, sheep, goats, alpaca, and llamas. They can die from the infestation. This parasite enters their brains and spinal cord rather than dwelling upon it in the meninges, though moose, for example, suffer more than elk.

The character of the infestation in elk has become an issue in the Idaho Legislature. The Elk Breeders in Idaho, a powerful group based on their many legislative victories, wants to change a state rule adopted in 1995. The rule prohibits the importation of elk from places where the meningeal worm is endemic. That is established to be east of the 100th meridian longitude.

Many eastern states are trying to reestablish elk. The Eastern Elk (Cervus canadensis canadensis) went extinct in 1877. Efforts to restore elk using Rocky Mountain elk (C. c. nelsoni) have been successful some of time, but in a number cases this “brainworm” from whitetails has caused the elk restoration to fail.

Whitetails in the West are free of the worm. As a result, western elk, mule deer, and moose are not infected. State wildlife agencies, hunters, wildlife lovers, environmentalists want to keep it that way. Elk breeders in Idaho certainly don’t want the parasite to show up, but their opponents say they are taking too big a risk by pushing to remove the ban on importing elk from the East.

Breeders say the risk of infestation is very low. They believe elk are an “end host” — elk cannot shed infectious fecal materia suitable to complete the parasite’s life cycle. However, a major study, “Meningeal Worm in Elk”, J. of Wildlife Management, 1992, reported experiments where elk calves were infected by whitetail derived worms. The infected elk then produced infectious feces, which then was used to reinfect whitetails and elk.

Last year’s July meeting with the Department of Ag saw only a portion of the stakeholders present – Fish and Game (opposed), the Department of Livestock and the breeders. The Idaho Department of Agriculture approved the rule change proposed by the elk breeders.

Virgil Moore, the director of Idaho Fish and Game wrote Moore, the Fish and Game chief, wrote to the Department of Agriculture, “Minnesota just recently eliminated moose hunting due to declines of over 50 percent in their populations in the last three years, in part due to substantial impacts from meningeal worm.” Other states in the region are stepping up precautions against importing the worm, he wrote – not loosening them.

Fish and Game and the elk breeders were the only stakeholders present and the proposed rule was adopted. Later, after they found out about it, sportsmen, wildlife enthusiasts, environmentalists were upset and said they had not been notified.

The Idaho Legislature can block new administrative rules by vote. The other stakeholders approached the 2015 session of the Idaho Legislature, and both the House Committee and the Senate Committee voted narrowly to reject the new rule. The close vote in the House Committee led its chair, Representative Ken Andrus, to have a revote the next day. He said one committee member wanted to change his vote. The new vote was a tie. So the rule was not rejected this time, but news reports are that Andrus made a procedural mistake. The vote is probably not valid. Andrus is suggesting his committee will now hold a procedurally proper vote.

Elk breeders say they want a new rule because they want to import some special genetics of eastern game farms. Critics suggest artificial insemination as a risk free method.

To complete its life cycle, the meningeal worm requires two hosts – deer or elk followed by slugs or snails and back to deer or elk.

The fertilized eggs are flushed from the brain to the lungs. The eggs hatch in the lungs; larvae are coughed up and swallowed. The emerge with the feces onto the ground/grass. There they reach out and penetrate small land snails or slugs that encounter the feces. Inside these gastropods they develop into larva that are infectious to deer, and we now know, elk. The deer/elk accidentally ingest the larvae when they are eating the grass and the life cycle is complete.

Interestingly in a similar way, prions (infectious deformed proteins) that cause the dread chronic wasting disease (CWD) are also taken up when an ungulate eats the infected soil around the grass. States are trying to keep wasting disease out or limit its spread too. Idaho is fortunate with no reported chronic wasting disease, and it does have a law from 2012 that puts up protective restrictions. Brain tissue samples from all the domestic elk adults that died or were harvested on the elk farms or ranches were to be submitted for testing.

Last year (2014) the new law was weakened in an effort by the elk breeders. Now only 10% must be submitted for testing.

Many believe that Idaho’s wild ungulates are at risk from CWD and could become from brainworm too. The elk breeders say the risks are so low that stringent regulations are not needed.

There has been a long running controversy in Idaho whether game farms will bring CWD to the state. It has appeared in game farms in a number of other states and provinces of Canada.



  1. Carter Niemeeyer Avatar
    Carter Niemeeyer

    Any risk, no matter how slight, is too much. If this parasite isn’t here and the potential harm to ungulates, like the moose, is presented by introducing the “worm”, then I would consider this “maneuver” reckless, political foolishness.

  2. Terry S. Singeltary Sr. Avatar

    I have postulated this for some time ???

    Saturday, December 21, 2013

    Parelaphostrongylus (Brainworm) Infection in Deer and Elk and the potential for CWD TSE prion consumption and spreading there from ?

    kind regards, terry

  3. Dr. Karen Bruhn Balch, DV Avatar
    Dr. Karen Bruhn Balch, DV


    The “risk” potential is exactly what Sen. Burgoyne said in commitee: “A lot of what we do in government is shift costs and shift risks from one group to another,” said Sen. Grant Burgoyne, D-Boise. “People are always asking us to do that, and it’s our job to decide if it’s appropriate. Here, the benefits (of lifting the import restriction) are pretty narrow for one small group, while the potential risk is broad. You can argue that risk is small, but if it comes to pass it would be devastating. The damage [to Idaho’s big game] would be extraordinary.”

  4. Eric T. Avatar
    Eric T.

    Rulon Gardner has elk farms in Idaho and Utah. Recently one of shooter bulls that was harvested at his Utah ranch tested positive for brainworm. Given that, the claim that the risk is miniscule falls flat.

    Also, any elk that Gardner has brought to idaho from Utah should be quarantined , put down and tested.

    1. skyrim Avatar

      I’d like to know how a guy goes from selling off his Olympic memorabilia in Bankruptcy to pay $4 Mil in taxes to this relatively new enterprise.
      I guess the Trustee isn’t looking to close or he’s into the Game Farm in name only.

  5. Immer Treue Avatar
    Immer Treue

    How ironic that the dafodils are all over E. granulosis, but to the best of my knowledge, nothing about this, something that has the real potential to send one on a long journey down a one-way river of no return.

    1. Immer Treue Avatar
      Immer Treue

      I should qualify above statement, Brainworm, the big danger to elk/moose, and CWD to humans. The moose of NW MN have all but disappeared, and very few wolves present, however, Whitetails with accompanying brain worm and liver flukes, you betcha!

  6. Ralph Maughan Avatar
    Ralph Maughan

    Good news! The Idaho State Senate passed the rejection of the Dept. Of Agriculture rule yesterday (March 12). The new rule was thought to increase the likelihood the brainworm would be introduced to elk, deer, or moose in Idaho.

    The Idaho House is yet to act.

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