Brucellowsis: A False Issue

InterTribal Bison Cooperative, 1997

Brucellosis is a contagious disease in domestic livestock caused by the bacteria Brucella abortus. The disease was originally transmitted to wildlife by cattle, and now is found in wild ungulates such as elk and bison of the Greater Yellowstone Area.

Bison in the Greater Yellowstone Area are being slaughtered under the guise of reducing or eliminating exposure of domestic cattle to brucellosis from wildlife. However, the real issue is not risk of exposure, which is minimal. The real issue is: who manages America's wildlife on public lands? Wildlife biologists and other wildlife professionals, or state or federal agricultural managers, whose perspectives and experience have nothing to do with wildlife management and conservation?

This paper sets forth the most important features of this issue and recommends possible solutions for the consideration of the Secretary of the Interior. Two key points must be noted at the beginning:

1. The states of Wyoming, Idaho and Montana and the Secretaries of Interior and Agriculture have established the Greater Yellowstone Interagency Brucellosis Committee (GYIBC) to help resolve the brucellosis problem. State wildlife agencies, veterinarians, agriculture departments, and the appropriate federal agencies, such as the Animal-Plant Health Inspection Service (APHIS), National Park Service (NPS), Bureau of Land Management (BLM), U.S. Fish and Wildlife Service (USFWS)) are members of the committee.
2. The GYIBC has failed to make any progress because only the National Park Service is willing to commit its share of the funding required to develop and implement a solution to the problem. APHIS is both unwilling to allocate funding to begin work on a solution and is attempting to promulgate new rules expanding its authority over wildlife. This directly violates the spirit and the specific requirements of the Memorandum of Understanding that established the GYIBC.

I believe that the conservation of wildlife resources must be vested in those state and federal departments and agencies whose primary mission is the protection, stewardship, and enhancement of wildlife resources. The brucellosis problem can be solved while assuring that our wildlife is conserved and managed by expert professionals under the overall authority of the Department of the Interior and state wildlife agencies.

What Is Brucellosis?

Brucellosis is transmitted during reproductive events. Although there is a very small chance that bison bulls could transmit the bacteria to cattle females during mating, the Greater Yellowstone Interagency Brucellosis Committee stated: "...transmission from bison to cattle is almost certainly confined to contamination by a birth event by adult females." Therefore, non-pregnant females, calves and male bison pose virtually no risk of disease transmission.

The most prevalent method of transmission is likely associated with exposure to an aborted fetus, placenta and fetal fluids. Uninfected young can also be infected from ingesting infected milk, because the bacteria can be passed through the milk.

The Brucella organism has limited viability outside its host and is quickly killed by direct sunlight. The bacteria can remain viable for longer periods of time in cold weather.

Is Brucellosis A Real Threat to Humans?

Human beings historically have contracted the disease by ingesting non-pasteurized milk, or by slaughtering and handling infected carcasses. Meat from infected animals can be safely eaten as long as the meat is adequately cooked. The widespread pasteurization of milk and near-elimination of the disease from cattle has reduced the number of reported human cases from 6,500 in 1940 to 70 in 1994.

The Centers for Disease Control no longer consider brucellosis a reportable disease. There is no evidence of humans becoming ill from ingestion of domestic American meats. The human incidence of brucellosis (called Undulant Fever) is currently restricted to consumption of unpasteurized goat milk and cheese from chronically infected Mexican goat herds.

Is Brucellosis a Real Threat to Livestock?

There has never been a verified case of transmission of brucellosis from a free-ranging wildlife population to cattle. Transmission has been demonstrated only under experimental conditions with confined animals.

In 1989, 810 cattle from 18 different herds where Yellowstone bison ranged were tested twice for brucellosis infection. No cattle tested positive for exposure to brucellosis.

The Greater Yellowstone Interagency Brucellosis Committee has recognized that bison bulls pose virtually no threat of infecting female cattle by mating.

Animals can be tested for brucellosis exposure by drawing a blood sample. The sample is then tested for the presence of immune reactors for brucellosis specifically. A positive test only means the animal has been exposed to brucellosis and its immune system has responded. It does not mean the animal is contagious. To determine if the animal is currently infected, the animal must be killed and appropriate tissue samples cultured for the Brucella organism.

A vaccine exists for cattle that is about 75% effective and a new vaccine has been developed that does not react positively to the brucellosis blood. No safe and effective vaccine exists for bison.

Predators and scavengers reduce the likelihood of the disease spreading because they quickly find and consume aborted fetuses and birth products, thus removing them from the environment.

Bison usually do not co-mingle with cattle during the calving season and cattle could be controlled on public lands during the vulnerable period. Cattle and bison can be separated in both time and space.

There is some evidence that Yellowstone's bison have developed a tolerance for the disease and do not experience many abortions. In fact, the Yellowstone bison population continues to grow, proof that brucellosis does not limit population growth. Only a few abortions due to brucellosis by Yellowstone's bison have been documented.

What Is APHIS Doing?

The Animal-Plant Health Inspection Service (APHIS) has spent over $3.5 billion since the 1930s to eradicate brucellosis. Today, only 57 cattle herds are left in the U.S. that test positive for brucellosis.

APHIS has committed to eradication of the disease by the end of 1998. The current annual budget for the brucellosis eradication program is $60 million. The elk and bison herds of Yellowstone stand in the way of that eradication goal.

Brucellosis eradication in domestic cattle is achieved by vaccination, test and slaughter and depopulation. If an animal or herd tests positive for exposure they are killed.

Nearly 2,000 bison have been killed in the Greater Yellowstone Area since 1984 for the perceived benefit of brucellosis control.

The prevalence of brucellosis is higher for the southern Yellowstone elk herds because elk are fed during winter on the National Elk Refuge and on 22 feedgrounds operated by the state of Wyoming. The Jackson bison herd also spends the winter on the National Elk Refuge.

What's Wrong With The APHIS Approach?

If APHIS prevails in its current policy, total control over public lands and public wildlife management could be transferred to the agriculture community.

If APHIS is successful in slaughtering all bison migrating from Yellowstone National Park, an abstract wildlife boundary will have effectively been established to keep bison inside Yellowstone. This may set a precedent for all migrating wildlife, grizzly bears, wolves, elk, eagles etc. Ultimately, APHIS and agricultural interests could propose a physical barrier around Yellowstone or other National Parks to keep the wildlife "in".

If APHIS establishes this precedent, it is only a matter of time before they move to eliminate the Yellowstone elk herd under the guise of brucellosis control. Ultimately, all wildlife could be managed intensively by both the state veterinarians and APHIS if they happen to be exposed to a disease of infected by a parasite.

If APHIS ultimately prevails, our wildlife will be treated like livestock, herded into corrals, held there and fed while tests are performed and infected members slaughtered. The remainder will be held in confinement or temporarily turned loose, only to be rounded up again and re-tested. Their wildness will be lost and our appreciation of that wildness diminished.

Regardless of the opinion of the state game and fish agencies, hunters and other wildlife advocates, APHIS could dictate how many, where and which wildlife species should be eliminated, especially on public lands.