Brucellosis research continues
Casper – “Brucellosis is that issue that seems to never go away,” opened Frank Galey, Dean of the UW College of Agriculture and Natural Resources in a lecture Aug. 17 at the 2011 Cattlemen’s Conference, hosted by the Wyoming Livestock Roundup and Double S Feeders.
The history of brucellosis extends back to the late 1800s when a man named David Bruce discovered the disease, and Brucella abortis, the strain affecting cattle, was discovered by Bernhard Bang just prior to the turn of the century. The first isolates of the bacteria were found in the early 1900s, and brucellosis was seen in the Greater Yellowstone Area at the end of the early 1900s.
While brucellosis has been a problem in the wildlife population for a number of years, loss of the calf crop in elk and bison was not seen as a paramount issue, according to Galey.
“Now that they have other things, such as wolves and grizzlies, eating the elk, the diminished herd size is important,” said Galey.
Both elk and bison carry brucellosis in Wyoming wildlife populations.
“There is a very large reservoir in the disease in wildlife,” explained Galey. “The disease keeps appearing because up to 80 percent of the bison in the Greater Yellowstone Area are seropositive and upwards of 20 to 30 percent of elk have been exposed.”
These exposed animals are likely to be affected or are affected by brucellosis.
“The elk on feedgrounds were traditionally thought to be the problem,” said Galey. “Now we are seeing higher prevalence in elk that are not fed artificially in places like western Park County.”
Galey added, “We aren’t sure how these numbers are going up, but there is some speculation that the increase in predation is causing bunching in larger numbers closer to cattle, which may cause higher disease prevalence.”
No vaccine strategy is currently present to handle the disease in wildlife, though it can be controlled in cattle by test and slaughter methods and through the use of vaccines.
The first big case of brucellosis in Wyoming cattle was in 2003 in Sublette County.
“In Teton County we had a second case and lost our brucellosis-free status in 2004. There was also a scare in Campbell County in 2004,” said Galey. “Last year in Park County we had three cases, two in cattle herds and one in a domestic bison herd.”
The last case of brucellosis was in January 2011, but it did not cost Wyoming its brucellosis class-free status. Of the infected herds in Park County, one cattle herd was released from quarantine and the other was retested in July, which revealed one suspect animal. The bison herd will be tested for a second time this fall.
A new boundary for the Designated Surveillance Area has expanded the area to include all of Park County and parts of Lincoln County where commingling with elk may be an issue.
Brucellosis in the United States is not specific to the Greater Yellowstone Area, according to Galey, who described cases in both Montana and Texas.
“This year they had their first case in Texas in over five years. It was a small herd with a total of nine reactors,” said Galey. “It was probably not a wildlife source in that case, and was likely a reservoir of infection from the past.”
Brucellosis also affects other countries and species outside of cattle.
“In Canada, outfitters have been given kits to test bison that are hunted off the park west of Calgary,” said Galey. “Brucellosis is all over, and is a big problem in Central Asia.”
“There is a very high prevalence of undulant fever in Central Asia,” explained Galey of the human form of brucellosis. Problems exist in goats, sheep and small ruminants as well, but limited resources in the area restrict research.
“They have some real problems with Malta fever, which is the goat brucellosis, and Biovis in their sheep,” added Galey. “Right now they pretty much live with it because they don’t have the funds to do much research. Maybe at some point we can cooperate and at least get access to some of their animals for research.”
Brucellosis is also present in reindeer and caribou herds around the world.
“One person estimated that they lost 20 to 25 percent of their calf crop,” said Galey.
The wide-reaching disease has been the subject of a number of regulations and research projects recently.
“In the College of Agriculture and Natural Resources we’re trying to put our money where our mouth is,” said Galey. “Our new immunology professor has an interest in the development of vaccines for exotic diseases. We also have a couple of molecular targets that make good candidates for new tests.”
Current tests only reveal if the animal has been exposed and not whether whether an active infection is going on, explained Galey.
He continued, “We have a live animal test at least in development to see if an animal is actually packing infection.”
Galey added, “We’re also working on a project for how these targets might fit into a new vaccine and looking at the impact of adult vaccination of cattle.”
Additionally, latent heifer studies are being done, since USDA is no longer supporting whole-herd depopulation when a positive case is found. Cooperation with the Wyoming Game and Fish Department also focuses on some elk studies.
In Louisiana, Texas, Iowa and Montana, academic facilities are working to develop new models, explore the genome of affected animals and develop new vaccines, said Galey.
To regulate brucellosis in the U.S., APHIS has adopted a new interim rule.
“If you had more than one case active at one time, it used to cost us our class free status,” said Galey. “Now more than one case inside the DSA won’t impact the entire industry.”
Depopulation of affected herds is also not mandated or the first choice of APHIS.
“I think that is more of an economic decision, and it is one that our coordination team is watching very closely,” added Galey.
The new rule also reduces the age of testing for intact cattle to six months of age. The U.S. has been declared brucellosis-free as a whole, and states will not lose their status as long as they develop MOUs.
Saige Albert is assistant editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.