College of Agriculture and Natural Resources researchers at the University of Wyoming continue to study brucellosis in wildlife. Brucellosis causes elk, bison, and cattle to abort fetuses and can also be transmitted to humans and cause undulant fever. Typically, animals will abort once and won’t abort again; occasionally, an animal will abort a second time, and rarely will abort a third time.
“Once they abort they are essentially immune for life, but they will be zero positive for the remainder of their lives,” said Walt Cook, University of Wyoming brucellosis coordinator.
Brucellosis was originally passed through unpasteurized milk. Since most of the milk in the United States is pasteurized, the disease isn’t as big of an issue as it is in other countries where it is a great human health concern. Brucellosis is an exotic disease that came from Europe and European cattle and was then transmitted to wildlife.
“We have eradicated the disease from livestock but occasionally get a disease spill over from elk transmitting over to livestock,” said Cook.
“One of the ways that we try to control brucellosis is through the use of vaccinations.”
Cattle in the United States have been vaccinated since the 1930’s with an original vaccine called strain 19. That vaccine was moderately affective preventing 60-70 percent of cattle from the disease. Strain 19 was later replaced by the rb51 vaccine.
“Again, it only protects 60-70 percent of the herd so that leaves 30-40 percent of the herd vulnerable, and because of that we are looking for better vaccines and that is what I have been involved in here at the university,” said Cook.
Several investigators at the University of Wyoming are looking at different vaccines. Gerry Andrews, associate professor in the Department of Veterinary Sciences and a medical microbiologist has developed unique vaccines.
“These vaccines haven’t been tested. They are in the early stages, but we are very excited and hopeful it can be a better vaccine for cattle,” said Cook.
Scientists are also interested in pursuing vaccines for wildlife, particularly elk; existing vaccines for cattle are not very effective on elk.
“That would be another avenue, but our emphasis now is on livestock,” said Cook
Elk on the feeding grounds can be vaccinated with strain 19. Researchers are able to inject the elk with what is called a “bio bullet,” which contains a freeze--dried pellet. The bullet is shot into a rear muscle of the animal and then breaks down to vaccinate the animal. That technique works pretty well but in a non-feeding elk population it becomes more challenging.
In the northwestern part of Wyoming, 20-40 percent of elk will test positive on the blood test, which means they were at some point exposed to the virus. That doesn’t mean they are actively spreading the virus. As one goes east of Yellowstone National Park into Park County, 5-15 percent of elk can be zero positive which shows they have been exposed to the disease and brucellosis has spread farther east.
“It is still a concern because we are seeing it where we normally haven’t been seeing it in our elk,” said Cook.
The farm bill approved use of funds for brucellosis vaccine research. “There could be significant funding for brucellosis vaccine research, and that would be a really good thing,” said Cook. “The University of Wyoming might be a great competitor for that, but there are lots of other places as well.”
Louisiana State University, Texas A&M University, Virginia Tech, and University of California, Davis, have conducted brucellosis research, but that has been reduced today because there is less brucellosis in the country. Researchers at the University of Wyoming are hoping to eventually receive money to continue brucellosis research efforts.