The health of wild sheep, as in any animal, is determined by multiple factors. Disease plays a large part, but stress, diet, population density, and changes in habitat can dramatically affect their health as well.

STRESS

When animals are continually exposed to stress, or experience a very stressful event, their immune system is suppressed and they are more vulnerable to disease. They will also experience increased difficulty fighting an infection. This is the same process that occurs when we have a stressful week, and then get a cold or the flu that weekend.

In many areas, wild sheep are believed to suffer from chronic stress. They appear to have a reduced ability to cope with stress when compared with other species. Some factors that cause stress to wild sheep include:

• Human disturbances
• Industrial activities
• Loss of availability or poor quality habitat
• Competition for food or space from grazing domestic animals, other wild animals or other wild sheep
• Low feed availability
• Poor quality feed
• Too many wild sheep on a small range
• Predators (coyotes, wolves, cougars, bears, eagles)
• Poor weather
• Infectious disease and parasites
• Contact with domestic sheep or goats

DIET

Diet can play a large part in an animals overall health. As we all know, it is not only important to eat enough food, but to eat the right kind of food to stay healthy. Wild sheep may experience a decrease in food availability from competition with other animals for food, habitat development, forest fires, invasive weeds, or poor weather to name a few. Even if appropriate food is present, it may be low in essential nutrients. Recent attention has been focused on trace mineral requirements for wild sheep, and locating regions where these may be deficient. More research is needed in this area.

DISEASE

All animals are susceptible to disease, but wild sheep have an unusual history of multiple large scale die-offs due to disease, namely pneumonia. This is complicated by the fact that wild sheep are susceptible to some of the diseases carried by domestic sheep and goats.

Pneumonia – the “Achilles Heel” of Wild Sheep

Pneumonia is the most prevalent and devastating disease in wild sheep. It is responsible for multiple large scale die-offs where entire herds can be reduced to a few individuals. Due to their remote nature, wild sheep have evolved without much contact to the bacteria and viruses that can lead to pneumonia. This makes them exquisitely sensitive when they do come in contact with these organisms.

Bacterial causes of pneumonia in wild sheep include Pasturella multocida (primarily Type A and Type F), Mannheimia hemolytica, Mycoplasma argini in bighorn sheep, and Mycoplasma ovipneumoniae in Dall’s sheep. Pasturella spp. tend to cause the most mortality. A high prevalence of Pasturella spp. at the time of lambing can cause 75-95% of the lambs to die within their first month. Wild sheep become infected with Pasturella primarily from direct contact with an infected individual, whether it is another wild sheep or a domestic sheep. Less common modes of transmission include contact with infected moist soil (Pasturella spp. can survive up to 12 hours in the right environment), or contact with aerosolized saliva when an infected animal sneezes up to several meters away.

Certain viruses affecting the respiratory system can cause disease and predispose the sheep to a bacterial infection as well. Some of these viruses are Respiratory Syncytial Virus (RSV), Parainfluenza Virus 3 (PI3), and Bovine Viral Diarrhea (BVD).

Pneumonia can, and is usually, caused by a combination of the bacteria and/or viruses mentioned above. The initial source of these organisms is thought to be domestic sheep or goats. Domestic sheep and goats have evolved with these organisms, and therefore can carry them without any sign of disease. Domestic sheep and goats that graze on the same territory as wild sheep are a big concern. A sheep farm that is located near wild sheep territory can also pose a problem. Some wild rams that are interested or attracted to domestic ewes will travel long distances to reach a sheep farm. If infected at the farm, the wild ram can carry organisms back to the wild and infect the whole herd. If an animal in the herd does not die from the infection, this individual may act as a “carrier” and be a potential source of re-infection of the herd during times of stress. Therefore, you can also see outbreaks of pneumonia in wild sheep even when they have not had recent contact with domestic animals. See Compatibility Between Wild and Domestic Sheep for more information on the interactions between wild and domestics.

Lungworms

Protostrongylus stilesi and Protostrongylus rushi are unique species of lungworm found in wild sheep. Many animals can become infected in moist regions where the lungworm’s intermediate host, the snail, survives. The lungworms can create lesions in the lungs and cause respiratory distress. These lesions can also make the wild sheep more susceptible to acquiring pneumonia.

Contagious Ecthyma

Wild sheep, domestic sheep and goats can become infected with Contagious Ecthyma (CE). CE is virtually endemic in all of these species, and is caused by the parapoxvirus orf virus. It is transmitted between species and among themselves by direct contact with affected animals or with contaminated surfaces and objects (fomites). CE creates scabby lesions in and around the mouth, face, udder, vulva, pizzle and lower limbs. Generally, affected domestic sheep and goats will be uncomfortable for a period and recover uneventfully. In wild sheep, severe outbreaks can occur where the crusting and erosions are so uncomfortable that they may become anorexic and some die.

Pink Eye

Pink eye is created by a bacterium called Moraxella bovis. It is common in cattle, and domestic sheep. It is not commonly a problem in wild sheep, but it can occur.

Lumpy Jaw

Lumpy Jaw is caused by a bacterium called Actinomyces bovis, which is a natural inhabitant in the mouths of ruminants. This bacterium will create lumpy jaw if there is an oral abrasion, puncture or opening where it can enter the tissue or bone. This occurs more often in cattle, and less frequently in domestic and wild sheep.

Parasites

In addition to lungworms, bighorn sheep are affected by many parasites including mites, ticks and gastrointestinal parasites. Parasites are normally not a major cause of disease in wild sheep.

Footrot

Footrot is an infectious disease that is of more concern in domestic sheep, but can occur in wild sheep. When the tissues around the hooves become compromised, certain bacteria can invade and infect the tissue. This leads to lameness and inflammation.

TREATMENT

Various treatments and management decisions have been attempted in order to care for the health of wild sheep. When herds of wild sheep become ill, it can be very difficult to reach them, catch them and administer treatment without causing more harm in the process. It is best to try and prevent the wild sheep from encountering stress, an improper diet and exposure to disease. Please visit the Helping Wild Sheep page to learn more about how wild sheep health is being managed in British Columbia and what you can do to help!

Free CWD Video Is Here and Now

The Chronic Wasting Disease Alliance (CWDA) and American Outdoor Productions (AOP) have partnered to provide a free, on-line chronic wasting disease (CWD) education video, reports the Wildlife Management Institute. Titled "Shedding Light on CWD," the video presents current and comprehensive status information on CWD and shows proper field-processing techniques for deer, elk and moose harvested in CWD-positive areas.

Nearly 35 minutes in length and offered at two connection speeds, the video contains 19 chapters such as "CWD Facts," "State Regulations," "Field Dressing Precautions" and "CWD Testing." Each chapter can be viewed independently to allow users to access targeted information that pertains to their specific question or concern.

Combining the production expertise of AOP and technical input from CWDA, "Shedding Light on CWD" was initiated in 2004. Originally available only through sales, the video became free for on-line viewing after CWDA purchased the rights to the production from AOP last year. Since then, the video has undergone extensive updating to make it current with the most recent CWD information, regulations and research available.

AOP currently is providing on-line hosting services for the video and will cooperate with CWDA to provide informational updates.

"American Outdoor Productions was proud to be a partner in this important project," said AOP’s Director of Business Bob Fiesthumel, "The synergy involved in developing this video was inspiring. We at AOP are happy to continue to play a role in ensuring that hunters throughout the CWD-affected states and provinces are provided only the best, up-to-date intelligence on this disease."

To view the video, visit http://www.cwd-info.org and click on the Watch Shedding Light on CWD link, or visit http://www.welcometohunting.com/video/CWD/cable/cwd.html to view or link to the video directly. (mcd)