News Release
November  8, 2007

Bluetongue kills more than 300 sheep in Big Horn Basin;

Producers urged to monitor flocks;
Virus also claims antelope and deer in state

           

Sheep producers in the Big Horn Basin and surrounding areas are urged to closely monitor their flocks for bluetongue, an infectious disease due to a potentially fatal virus.

 

An outbreak of bluetongue this fall has killed more than 300 sheep in the Worland, Otto, Basin and Greybull areas of the Big Horn Basin and led to sickness in hundreds of other sheep.

 

The virus also killed pronghorn antelope, white-tailed deer and mule deer in the Big Horn Basin as well as antelope and mule deer in the Cody, Sinclair and Douglas areas. The disease is also present in southern Montana.

 

Although the incidence of acute clinical disease should subside with the onset of cold weather, sheep owners are urged to contact their veterinarian if they notice symptoms of bluetongue in their flocks, said Don Montgomery, director of the Wyoming State Veterinary Laboratory (WSVL), which is managed by the University of Wyoming’s College of Agriculture.

   

Montgomery said samples from sheep (either live or dead animals) can be collected and sent to the WSVL for testing.

 

“We may see additional losses due to abortion, particularly in sheep but conceivably in cattle; however, infections in cattle are generally not apparent. This could occur even after a hard freeze kills the midges,” Montgomery said. The disease is transmitted by a small Culicoides biting midge, commonly called “no-see-ums.”

 

“Bluetongue crosses the placenta and causes fetal malformations. Delayed death losses may also occur due to aspiration pneumonia because the viral infection damages the muscles involved in swallowing. We are most likely to see this in the Big Horn Basin along the affected drainages,” Montgomery added.

 

UW Department of Veterinary Sciences Professor Donal O’Toole said this has been an unusual year for bluetongue in Wyoming.

 

“We don’t usually see high death loss like we have this fall,” O’Toole said. “The outbreak this year may reflect a cycle of waning natural immunity to the virus. If woolgrowers see an outbreak of lameness or sore mouths in their flocks, they should work with their veterinarian to establish whether it is bluetongue rather than orf or other common diseases of sheep.” Orf is a highly contagious disease of sheep and goats caused by a parapoxvirus.

 

O’Toole added, “We can confirm a clinical diagnosis of bluetongue if veterinarians submit blood samples from live sheep or organ samples from dead sheep.”

 

Lesions seen in the current outbreak include inflammation of the feet, crusting around the nose and mouth, and swollen lips. Bluetongue’s distinctive name is due to blue discoloration of the mouth and lips of infected animals. Pneumonia is usually the cause of death in affected sheep.

 

There is no risk to human health from bluetongue, and, though the virus can infect cattle, it does not usually cause disease, O’Toole said. When wild animals are affected, such as antelope or deer, they are usually found terminally ill or dead, generally close to water sources.

 

The outbreaks in wildlife and sheep in the Big Horn Basin are being investigated by the Wyoming Livestock Board (WLSB) in collaboration with the WSVL, area veterinarians, wool growers, U.S. Department of Agriculture (USDA), and Wyoming Game and Fish Department (G&F).

 

The outbreak of a bluetongue-like disease was first recognized in wildlife in mid-September by the G&F. A press release issued by the G&F reported deaths in pronghorn, white-tailed deer and mule deer. The role of bluetongue in the wildlife die-off was confirmed in mid-October.

 

As of Nov. 8, the WSVL had confirmed infection in sheep on seven ranches in the Worland, Otto, Basin and Greybull areas. Lambs and adult ewes have died, with deaths tending to occur among older ewes.

 

Veterinarian Tim Graham from Basin reports that approximately 300 of 900 affected sheep in one range flock died from the infection.

 

Livestock premises with confirmed infection have been quarantined. 

 

Bluetongue is a warm-weather disease due to the insect vectors. Signs subside after the first hard frost, since freezing temperatures kill the insects that transmit the disease. Thus, quarantines are expected to be lifted soon.

 

There are unconfirmed reports of the disease affecting other Wyoming flocks, but, to date, none of these occurred outside the Big Horn Basin. 

 

O’Toole said treatment is symptomatic.

 

“It involves support and nursing care. Because the mouth is so sore, sheep are reluctant to eat. Valuable animals may have to be fed by a stomach tube, which producers in the Big Horn Basin are doing,” he said. “Animals need to be given shade and access to water, and they need time to recover.”

 

Antibiotics aren’t used to directly treat bluetongue since it’s a virus, but sometimes antibiotics are given to reduce secondary infections, he said.

 

Preliminary results of wildlife cases indicate the strain of bluetongue virus in this year’s outbreak is not unusual for Wyoming.  Most have occurred in the Big Horn Basin, but small numbers of affected pronghorn and mule deer have also been diagnosed near Sinclair (south central Wyoming) and Douglas (eastern Wyoming).

 

Losses in livestock have not been confirmed in areas outside the Big Horn Basin.

 

It is important that producers who suspect the disease report it to the WLSB and work with their veterinarian to establish whether bluetongue is involved. Typically, this involves submitting blood (from live sheep) or tissue (from dead sheep) samples to the WSVL. 

 

Images of bluetongue are available on the WSVL Web page at http://wyovet.uwyo.edu/Diseases/2007/gross_lesions_of_bluetongue_in_s.htm.

 

Contact information follows:

            Sheep

1.    Questions about regulatory issues – WSVL, (307) 742-6638 or WLSB, (307) 777-7515.

2.   Questions about clinical signs – Veterinarian Tim Graham (307) 568-2967.

3.   Questions about test samples – WSVL.

            Wildlife losses

1.   Regional G&F offices (contact information is at http://gf.state.wy.us/admin/regional/index.asp).

2.   G&F Assistant State Veterinarian Cynthia Tate, (307) 742-6638.

Contact: Robert Waggener, Editor
Phone: (307) 766-3571
E-mail: robertw@uwyo.edu

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