Brucellosis report: Disease blamed for death of bighorns

By SCOTT McMILLION, Chronicle Staff Writer

An accidental exposure to brucellosis caused the death of most of the bighorn sheep at a research facility in southeastern Wyoming, according to a researcher there.

In addition, one wild bighorn in the Jackson area has shown possible signs of exposure to the disease, said Terry Kreeger, who works with wildlife diseases at Wyoming Game and Fish's State Diagnostic Laboratory near Cheyenne.

"This is the first report ever of brucellosis in (bighorn) sheep," Kreeger said, although it has been reported in domestic sheep.

The disease causes painful flu-like symptoms in people and in cattle, bison and elk it causes spontaneous abortions. But it is not considered a fatal disease in those species.

For bighorns, it could be more serious.

"We think they may die from it," Kreeger told the technical committee of the Greater Yellowstone Interagency Brucellosis Committee on Tuesday.

He speculated that brucellosis might play some role in some the dieoffs of bighorns around the Yellowstone National Park area.

Live bighorns have been tested often for the disease, but dead ones haven't.

The research facility's bighorns were kept in a 350-acre pasture that shared a fence with elk from northwest Wyoming that had been thought to be free of brucellosis. However, a unique strain of the disease erupted in one animal after it was impregnated as part of a research project.

"This is a bad bug," Kreeger said. "It hides from you."

That animal then aborted along the shared fenceline in March 2000, and the bighorns likely came into contact with the fetus, Kreeger said.

Researchers later noticed one ram had badly swollen testicles and the animal was killed. An investigation revealed abscesses and adhesions on those organs, a typical sign of brucellosis.

The other bighorns in the enclosure were tested and all positive animals were killed, Kreeger said. One ram that was found dead suffered from the disease.

Of about two dozen bighorns, only a handful survive today, he said.

The possibly infected wild bighorn was discovered about six weeks ago and was one of 10 animals tested, Kreeger said.

Brucellosis has been the focus of debate and acrimony for years, but most of it focused on the threat of it spreading to cattle.

Now, Kreeger said, bighorns could be at risk.

The discoveries mean brucellosis could pose "an unknown risk to bighorn sheep."

SIDEBAR: Elk may have infected Wyoming cattle herd

State and federal investigators have focused their investigation on other livestock as the likely source of a recent brucellosis outbreak in a Wyoming cattle herd, they told a group of scientists gathered here Tuesday.

However, if no leads arise in that venue, they'll start looking at elk as a source of the disease.

"You don't have to be a rocket scientist to at least surmise that the infection may have come from the elk," Jim Logan, Wyoming state veterinarian, told a technical committee of the Greater Yellowstone Interagency Brucellosis Committee.

The disease was found in a Sublette County, Wyo., herd late last year.

"If we don't find anything of a livestock origin, we'll have to look at other possible origins," said Arnold Gertonson, a veterinarian who specializes in brucellosis for the federal Animal and Plant Health Inspection Service.

Brucellosis is a bacterial disease spread primarily through contact with infected birthing material or aborted fetuses and can cause cattle to abort. It has been eliminated from almost all cattle herds in the nation, but a reservoir of the disease exists in the bison and elk herds in and near Yellowstone National Park.

In Montana, occurrence of the disease is low in elk, usually running at less than 5 percent. In Wyoming, where elk gather in the winters at state and federal feedgrounds, the prevalence runs as high as 50 percent.

The nature of the disease means it is spread primarily through female animals.

Wyoming's Gov. Dave Freudenthal has ordered all female cattle in Wyoming to be tested for brucellosis within 60 days of their sale, a big job that is costing the cattle industry money.

No female animals have been introduced to the infected cattle herd since 1975, Logan said, although bulls have been brought in for breeding.

Vaccination didn't halt the disease.

The owners of the infected herd had vaccinated their animals "as far back as we can get records on them," Logan said.

Existing vaccines are only about 50 percent to 60 percent effective, according to David Pascual, a researcher at Montana State University.

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