Hunters Help With Brucellosis Surveillance

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During the 2005-06 hunting season, hunters voluntarily took blood samples from nearly 900 elk in western Wyoming. Hunters were asked to take part in studies to determine brucellosis seroprevalence rates, or if the animal has been exposed to the disease, in herds of interest around the Jackson/Pinedale region and as part of the Governor's Brucellosis Coordination Team's recommendation to increase sampling throughout the state.

Last year the Wyoming Game and Fish Department surveyed the southwest quadrant of the state by mailing approximately 5,000 sampling kits to hunters with licenses in that region. Of those kits, 343 were returned with useable elk blood samples and a single elk was determined to be seropositive.

The positive elk was found just east of Lander. "This elk was very close to the brucellosis endemic area," said Hank Edwards, Game and Fish wildlife disease specialist. "Historically we haven't found any seropositive elk outside of the brucellosis endemic area in northwest Wyoming."

Elk in southwest Wyoming are not supplementally fed on feedgrounds as the animals are in the Jackson/Pinedale area, where brucellosis rates are much higher. Historically, seroprevalence has ranged from 2-3 percent in elk outside of feedground areas, presumably because these are elk that have interchange with the brucellosis endemic region. In 2004, for example, 1,500 sampling kits were sent to hunters in northeastern Wyoming and all samples that were returned tested negative.

An elk is determined to be seropositive through multiple blood tests that indicate that an animal has been exposed to Brucella abortus, the bacteria causing brucellosis, through antibodies found in the blood. Seropositive results do not necessarily mean that an animal is currently infected or can transmit the disease to other elk or livestock.

Elk and bison were again tested around Jackson, as part of ongoing disease surveillance. This past year, successful hunters in Grand Teton National Park and the National Elk Refuge were asked to participate in a voluntary brucellosis surveillance program.

In bison, brucellosis seroprevalence continues to remain high. Of the hunter-harvested bison in 2005, 66 percent were seropositive, as compared to the five-year average of 60 percent.

"We were really successful in obtaining a large sample size this year," said Jill Miller, Game and Fish brucellosis feedground habitat biologist, who led the Jackson portion of the surveillance effort. "I would like to thank all the agency personnel who were involved, and especially hunters for their efforts. Without their cooperation, we would be unable to survey the health of this herd."

The seroprevalence of this portion of the Jackson Elk Herd was found to be 14 percent of all animals surveyed. The animals targeted in this hunter surveillance included those that would likely spend the winter on the National Elk Refuge.

Brucellosis transmitted to cattle herds from elk caused Wyoming to lose its brucellosis free status in 2004. Ongoing research and surveillance is part of the effort to eliminate brucellosis and gain brucellosis free status back to the state.