Bighorn Sheep

Health Issues Which May Affect This Animal

What Causes This Disease?

Brucellosis in elk, bison, and cattle is caused by Brucella abortus. There are a variety of other Brucella species can affect sheep (B. ovis), goats (B. melitensis), pigs, caribou and reindeer (B. suis), dogs (B. canis), and several species of marine mammals.

Where Is The Disease Found?

Brucellosis is found worldwide in livestock, but most countries have control or eradication programs to control or eliminate the disease. Brucellosis has largely been eliminated from domestic livestock in North America. A reservoir of brucellosis occurs in elk and bison in the Greater Yellowstone Area which includes eastern Idaho. Because wild ungulates and cattle share range, disease transmission to domestic cattle is of great concern.

Signs of Disease

There are no obvious signs of brucellosis in infected animals. Abortions can occur in the middle trimester of pregnancy. Elk infected with brucellosis may abort between January and June. There are no typical outward signs of Brucellosis in most animals. Males that are infected with brucellosis may have swollen testicles or swollen joints. In chronic infections can lead to infertility in both males and females..

Read More About Brucellosis

What Causes This Disease?

Contagious ecthyma is caused by a poxvirus. In domestic sheep and goats it is known as Orf. Orf is spread by direct contact with lesions or scabs from infected animals to humans and other animals.

Where Is The Disease Found?

Contagious ecthyma occurs in domestic livestock and wild ruminants throughout North American, but it occurs rarely. Contagious ecthyma has not been documented in Idaho.

Signs of Disease

In animals, contagious ecthyma causes fluid-filled blisters with thick scabs on lips, mouth, nose, eyelids, ears and teats. The scabs on the mouth may make it difficult or painful for the animal to eat and some animals may appear weak. If scabs are on the feet, animals may find it painful to walk normally. Scabs on the teats may cause females to not let young nurse.

Read More About Contagious Ecthyma

What Causes This Disease?

Epizootic hemorrhagic disease (EHD) is caused by a virus in the genus Orbivirus. There are two distinct types of EHD in North America, and about 16 types of BT. The virus is spread between susceptible animals by biting midges (Culicoides spp.).

Where Is The Disease Found?

EHD is found throughout North America from the southeast to the northwest. EHD and bluetongue have been documented in most areas of Idaho with large outbreaks in white-tailed deer in the Clearwater Region.

Signs of Disease

Clinical signs in infected deer include sluggishness, difficulty breathing, and swelling of the head, neck and tongue. Ulcers or erosions of the tongue or gums may be present. Internal lesions include swelling and fluid accumulation in the lungs, ulcers in the abomasum an d hemorrhages on the heart and intestines. Animals with chronic EHD can have abnormal hoof growth, hoof sloughing and sometimes are emaciated..

Read More About Epizootic Hemorrhagic Disease

What Causes This Disease?

The most common pathogens in bighorn sheep are respiratory bacteria Pasteurella haemolytica or Pasteurella multocida, and Mycoplasma ovipneumonia but respiratory viruses like Infectious Bovine Rhinovirus, Parainfluenza virus, Bovine Respiratory Syncytial Virus, or parasites like lungworms can contribute to pneumonia in bighorns and other ruminants. There is evidence in captive and free-ranging bighorn sheep that transmission can occur after contact with domestic sheep or goats. Other ruminants can develop pneumonia from these and other bacteria including Arcanobacter spp., Corynebacterium pseudotuberculosis, and Trueprella pyogenes as well as a variety of respiratory viruses.

Where Is The Disease Found?

Generally, pneumonia is a problem in bighorn sheep and to a lesser extent in deer and elk. Pneumonia in bighorn sheep has been found throughout North America. In Idaho, pneumonia in bighorns has been found in all areas where bighorn sheep exist. Isolated cases of pneumonia have been documented in mule deer, white-tailed deer, elk, moose, pronghorn and mountain goats in Idaho.

Signs of Disease

Clinical signs of pneumonia in ruminants include coughing, shortness of breath, and a weakened condition. Generally, animals with pneumonia will have discolored lungs possibly with adhesions to the rib cage or abscesses. In trials of captive bighorn sheep that are inoculated with Pasteurellaceae bacteria, survival is generally less than 2-3 days. Depending on the bacterial pathogen present, the nutritional and immune status of the individual, and other factors, affects range from chronic pneumonia in adult females, summer lamb mortality events and ill thrift to rapid whole herd mortality events . Often the mortality events are found by hunters or during herd surveys when carcasses or skeletons are found. Similar signs of disease occur in other ruminants affected by pneumonia but pneumonia in other species of ruminants tends to occur in single individuals rather than on a herd basis.

Read More About Pneumonia

What Causes This Disease?

Several species of tapeworm produce cystercerci in the intermediate host. The most common in cervids is Taenia hydatigena, but other species including T. pissiformis and T. krabbei.

Where Is The Disease Found?

Tapeworm cystercerci are found in appropriate ruminant hosts across most of North America. They are commonly reported in ungulates in Idaho.

Signs of Disease

Cystercerci are usually small bladders, approximately 0.5-2 cm in diameter, containing fluid and a single larval tapeworm. The location of the cystercerci depends on the tapeworm species and the host species. Taenia hydatigena and T. pissiformis typically form cystercerci in the mesenteries or the liver. Taenia krabbei typically forms cystercerci in the skeletal muscle. There also may be white, star-like scars on the surface of the liver from the migration of larval tapeworms. Carnivores like wolves, coyotes and foxes are the definitive host of the adult tapeworms and usually appear healthy even though they may be infected with large numbers of tapeworms.

Read More About Tapeworm cysts (Cystercerci)

What Causes This Disease?

Winter ticks are a one-host tick of ungulates. Large numbers of ticks can cause anemia due to blood loss, hair loss due to excessive grooming, and poor body condition due to inadequate food intake.

Where Is The Disease Found?

Winter ticks are present in nearly all areas of ungulate distribution in North America except for Alaska. Winter ticks have been identified in most ungulate species in Idaho.

Signs of Disease

Winter ticks are usually not seen on animals in the larval or nymphal stages as these are relatively small. The adult males and females are the same size as typical wood ticks. The engorged adult females can be 1-2 cm in diameter. Moose, elk and deer with large numbers of winter ticks often lose significant amounts of hair, especially in late winter. Some of these animals may be lethargic and appear weak from loss of blood, hypothermia and inadequate nutrition.

Read More About Winter ticks


  • Bighorn Sheep / Photo by Gary Powers

    California man wins bighorn sheep tag in lottery

    John M. Taylor of Arroyo Grande, California was the lucky winner of a hunting tag from the 25th Annual Bighorn Sheep tag lottery drawing July 26 at Idaho Fish and Game Headquarters. The tag is offered under a partnership between Idaho Wild Sheep Foundation (WSF) and Idaho Fish and Game.

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    Owyhee Wilderness California bighorn sheep lamb survival study

    Jake Powell was able to spend several days on the East Fork Owyhee River monitoring bighorn sheep lamb production.  In March of this year, I spent several days with a team of biologists capturing and radio-collaring bighorn sheep as part of this study. Here is some video from the field.

  • Bighorn Sheep / Photo by Gary Powers

    Moose, goat, and sheep controlled hunt results available online

    Results of the drawings for moose, bighorn sheep, and mountain goat controlled hunts are now available online.

    Check results

  • Bighorn ram running

    Moose, sheep and goat controlled hunt application deadline approaching

    Hunters, anglers and trappers are also reminded they will see new prices starting May 1 with an additional $5 Access/Depredation fee for resident adults and $10 for nonresident adults when they buy their first annual license.

  • Bighorn sheep on rockslide

    Another bighorn euthanized after contacting domestic sheep near Challis

    A one-year-old bighorn sheep ram that mingled with domestic sheep near Challis was euthanized Friday, April 14, to prevent the sheep from potentially carrying disease back to the wild herd. This is the third bighorn sheep removed from the same area on the edge of Challis since March 30.

    Idaho Department of Fish and Game officials euthanized the yearling ram after receiving reports that it was observed inside a pen on private property with a small flock of domestic sheep.

  • Bull moose in yellow grass

    Apply now for moose, bighorn sheep and mountain goat hunts

    The application period for moose, bighorn sheep and mountain goat controlled hunts is now open. Hunters have through April 30 to apply.

    Hunters can apply at any Fish and Game office, license vendor, or use a credit card by telephone or over the Internet. Telephone applications may be made at 1-800-554-8685. Internet users may apply through Fish and Game's website at Mailed applications must be postmarked no later than April 30.

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    Bighorns euthanized after contacting domestic sheep in Challis

    Two bighorn sheep rams that were in immediate proximity to domestic sheep near Challis were euthanized Thursday, March 30, to prevent the sheep from potentially carrying disease back to the wild herd. One ram was a five-years-old and the other a six-year old.

  • Bighorn Sheep / Photo by Gary Powers

    Moose, sheep and goat rules available soon

    Idaho's 2017 and 2018 moose, bighorn sheep and mountain goat seasons and rules booklet arrived from the printer and should be available at Fish and Game offices and license vendors later this week.

    They are available online now at

  • Super Bowl Sunday Bighorn Sheep Capture in Hells Canyon

    Low flying helicopters deploy net guns to capture bighorn sheep in Hells Canyon on Sunday. Sheep are transported to processing site where researchers measure overall sheep body condition and take samples to test for disease. Animals are marked with a collar and ear tag to monitor movement and survival rates.



  • Redbird Ram

    Hells Canyon Bighorn Sheep Capture Underway

    The Idaho Department of Fish and Game, Oregon Department of Fish and Wildlife, and Washington Department of Fish and Wildlife plan to capture 100 bighorn sheep in five Hells Canyon herds February 2nd –14th as part of the ongoing Hells Canyon Initiative to restore bighorn sheep populations. 

    Bighorn sheep will be captured by net gunning from a helicopter and brought to a processing site near the capture location. Biologists will take health samples, radio collar the sheep, and release them on site. 

Bighorn Sheep

Ovis canadensis

IDAPA Classification: Big Game
View Species Profile