Study a blow to elk feeding
Authors say practice of test-and-slaughter may lead to more, not less, brucellosis in elk.
Wyoming Game and Fish Department officials coax a group of elk into a holding area of the state's largest elk trap at the Muddy Creek feed ground, about 25 miles south of Boulder, Wyo., earlier this year. The operation is part of a controversial test-and-slaughter program that researchers say may increase brucellosis among elk. NEWS&GUIDE PHOTO / PRICE CHAMBERSView our entire photo gallery >>
By Cory Hatch
September 6, 2006
Brucellosis management in Wyoming, especially congregating elk on feed grounds, only exacerbates the disease and flies in the face of current disease-prevention research, according to a recent review.
The study, printed in the journal Frontiers in Ecology, also takes issue with current test-and-slaughter procedures and suggests changes for vaccination programs in both elk and bison.
The paper says that states without winter feed grounds, such as Montana, see brucellosis in zero to 3 percent of the elk population, while Wyoming herds average 34 percent, ranging up to 80 percent in extreme cases. Brucellosis is a bacteria that has the potential to spread from wildlife to infect stock.
Transmission from elk to cattle in Sublette and Teton counties led the federal Animal Plant Health Inspection Service to rescind the state’s brucellosis-free status. Two Jackson Hole cattle herds were destroyed and stock shipped from Wyoming must now undergo more extensive surveillance, to the economic detriment of ranchers.
Brucellosis causes undulant fever in humans and is the reason for pasteurization. How to combat it in Teton County has opened a debate between conservationists and sportsmen centered mainly on feed grounds.
One of the paper’s authors, freelance researcher Leslie Bienen, said phasing out feed grounds would likely reduce or eliminate the disease in Wyoming, given enough time. But she also recognizes that feed grounds are a political football and may not be easily eliminated, if at all.
“Every model that I’ve ever seen shows that it [brucellosis] would likely die out in elk unless they got it back from cattle,” Bienen said in a telephone interview. “Natural behavior doesn’t congregate elk like that. It wouldn’t spread through natural behaviors without feed grounds.”
Further, the paper suggests that proper management of brucellosis is crucial to counter more serious diseases like chronic wasting disease, a condition similar to bovine spongiform encephalopathy (“mad cow” disease) that kills 100 percent of infected animals.
“A wide range of disease ecologists and [Wyoming Game and Fish Department’s] own officials are in agreement that [chronic wasting disease] will eventually reach Wyoming’s feed grounds,” the paper states.
Bienen and co-author Gary Tabor make recommendations for controlling brucellosis in elk, including gradually phasing out feed grounds. Over the long term, the plan suggests wildlife officials “end routine feeding of elk anywhere in the GYE [greater Yellowstone ecosystem], except on an emergency basis.”
The recommendations also include protecting and enhancing winter habitat for elk.
As for test-and-slaughter, Bienen says that current efforts to reduce brucellosis in elk herds actually encourage brucellosis rather than stem the disease.
The current test-and-slaughter program at the Muddy Creek feed ground removes roughly 10 percent of the population. But the removal of these brucellosis-positive animals includes some animals that have developed a natural resistance to the bacterial infection, leaving only naive elk – those that haven’t been exposed to the disease – in the herd.
Keeping these resistant animals alive acts in a similar way to vaccination. Killing these animals, and leaving only naive elk, can actually increase disease transmission, according to the study.
For bison, the most recent test-and-slaughter models suggest that eliminating brucellosis would take 50 years and would require killing almost all the animals in the herd. In Montana, a long-standing test-and-slaughter program actually increased brucellosis prevalence from 40 percent to between 45 and 50 percent.
Suggestions for test-and-slaughter programs include an experiment comparing the Muddy Creek test-and-slaughter program with a Gros Ventre feed ground phase-out to see which method yields the lowest brucellosis prevalence over a five-year period.
The authors also suggest diverting money currently used for other test-and-slaughter programs into research programs for more accurate diagnostic tests. Today elk and bison are tested for brucellosis by drawing blood. But those tests reveal whether elk have been exposed to the disease only, not whether they are infected.
The way to determine infection is by testing organs, a feat accomplished only by killing the animal. Infection percentages are well below those for exposure.
Vaccination programs also present a problem. In bison, the vaccines seem to work well, and scientists estimate that they could eradicate brucellosis within several decades if 40 to 50 percent of bison were “consistently” vaccinated.
But in elk, Strain 19, the vaccine commonly used in Wyoming, has a poor reputation.
“The vaccination of elk works very poorly, if at all,” Bienen said. “It [the disease] seems to decrease a little bit, and even that is controversial.”
Bienen and Tabor suggest widespread use of a new vaccine, RB51, as soon as officials determine that it is environmentally safe. Also, funds should be increased for efforts to develop more potent vaccines.
While Bienen says that, at least for elk, a hands off approach coupled with the elimination of feed grounds might yield the best results, environmentalists must recognize that this is impossible.
“Conservation groups and wildlife groups have to live with the concept of intervention,” she said. “Even if leaving those populations entirely alone was a reasonable solution, politically it’s not.”
Further, wildlife managers and scientists must understand the difference between laboratory experiments and the factors that confound brucellosis elimination efforts in the wild.
“There’s no closed system,” she said. “There’s no such thing as a truly clean herd.”