Spread of Bighorn Sheep Pneumonia Continues


By Jule Banville, NewWest.net guest blogger 8-23-10

The deadly spread of pneumonia in Montana’s bighorn sheep population picked up momentum west of Anaconda, where a hunter alerted Fish, Wildlife & Parks of possible disease in the Lost Creek population. Biologists killed four sheep and confirmed through lab work they were infected. FWP announced the latest outbreak today, which occurred in the sixth bighorn sheep population in west central Montana.

FWP, in its killing of suspected sick sheep, is continuing an experimental and aggressive battle against the easily spread and usually fatal respiratory disease.

“We’re too early in this to know everything we’d like to know. But, until we are able to survey and collect more sheep, we have to proceed as if we are dealing with a pneumonia outbreak,” said FWP Wildlife Biologist Ray Vinkey. “We can’t afford to miss the chance of removing the last sick sheep before they infect the rest of the population. Right now we’re taking it one day at a time.”

A hunter, Wayne Estay of Butte, first reported signs of sick sheep west of Anaconda during a preseason scouting trip on Aug. 17.

Vinkey and another FWP wildlife biologist, Jay Kolbe, responded and shot the sheep that exhibited clinical signs or behavior suggesting pneumonia. According to an FWP news release, they collected blood and tissue samples for further analysis at the FWP wildlife lab in Bozeman. Autopsies showed everything from early to advanced infection in the lungs, which in the worst case had also compromised the heart and liver. The varying stages of infection suggest that the disease is spreading over time.

Other pneumonia outbreaks affected bighorn populations in the East Fork of the Bitterroot late last fall and in the Bonner area and Lower and Upper Rock Creek herds in January and February. Most recently FWP detected pneumonia in the Skalkaho population east of Hamilton on Aug. 9 (see NewWest’s story).

Last fall, FWP began killing sick sheep from the East Fork and Bonner populations to try to protect healthy animals. Officials allowed the disease to run its course in Lower Rock Creek, however, due to terrain and difficulty in finding and approaching the bighorns there. The disease also ran its course in Upper Rock Creek, where it was too widespread to try to control. Bighorns wandering to or from Rock Creek could have spread the disease to the Anaconda herd this summer, but the source may never be proven, according to FWP.

“Our experience so far in the East Fork of the Bitterroot demonstrates that killing sick sheep can succeed in saving the rest of the population,” said Mike Thompson, FWP Region 2 Wildlife Manager. “This kind of work is hard on everyone.  But, the key is early detection and a quick, aggressive response.”

Chris Anderson, a student volunteer with FWP from the University of Minnesota, documented the survival of 32 lambs per 100 ewes in the East Fork this summer, where FWP removed 80 sick individuals last fall and winter, and at least 87 seemingly healthy sheep remain. But where FWP let the disease run its course last winter, Anderson was unable to find any lambs that had survived exposure to the pathogens persisting in Rock Creek bighorns. He reports landowners have found dead lambs and sick adults in that area this summer.

The Lost Creek herd was established in 1967, with help from the Anaconda Sportsmen’s Club, when 25 bighorns were transplanted from the Sun River herd. More than half of the population was lost to pneumonia in 1991, but has since recovered to number at least 297 sheep. Twelve hunters hold either-sex licenses and 30 hold ewe-licenses for this hunting district, which are valid beginning Sept. 5. FWP will contact hunters as more becomes known about the outbreak.

There have been no known cases of humans or pets contracting pneumonia from wild sheep, but FWP cautions anyone who finds dead or sick bighorn sheep to leave the animal alone. FWP also encourages the public to immediately report any observations of sheep exhibiting symptoms of an illness or strange behavior.

“Reports from the public were responsible for the first detection of pneumonia in most of our recent outbreaks,” said Vinkey. “These reports from the public help us determine how widespread the sickness is and give us a chance at catching it in its early stages.” 


Originally posted at NewWest.net