Wyoming State Veterinarian reviews causes, control strategies for brucellosis in the state
Worland – Wyoming State Veterinarian Jim Logan says he could talk about brucellosis all day long, and that he doesn’t think it will go away during his career, as it’s not only a bacterial disease, but also a political disease.
“The political aspects make it extremely difficult to clear up,” said Logan to a group of producers gathered at WESTI Ag Days in Worland on Feb. 1.
The bacteria brucella abortus can be spread during a birthing event from an infected animal – an abortion or live birth – and it can cause ungulate fever in humans.
The disease is spread through ingestion, and Logan said one abortion from an infected cow, in theory, contains enough bacteria for over 10,000 infective doses.
“Susceptibility is related to age. Young animals – newborns, heifers and yearlings – are more likely to be infected, and pregnancy status plays a role,” he explained, adding that late-term pregnancy is the best time to test for brucellosis, because that’s when the bacteria is at its highest concentration in the bloodstream.
Trace-outs from infected herds now go back to cattle sold from that herd over the preceding year, because of the disease’s variable incubation period.
“We’re not sure when the infections in Meeteetse showed up,” said Logan of the latest two herds with cases of the disease. “We know when we found them, but not when the exposure occurred, so we’ve got to go back at least a year to test cattle sold out of both of those herds to make sure they weren’t just incubating and negative on the test at the time of sale. The testing on trace-outs is done to protect the producer who bought those cattle so he doesn’t end up with brucellosis in his herd.”
Logan said the best prevention is still to keep female cattle away from bison and elk.
“The elk in the Greater Yellowstone Area (GYA) and Designated Surveillance Area (DSA) are heavily infected with brucella abortus,” he said. “A problem with the elk is that, according to Wyoming Game and Fish Department reports, their calving season, along with bison, has been extended farther into the summer. A lot of the reason for that is the wolves are bothering them during their natural breeding season, and as a result they’re not all getting bred up early in October and November and they’re calving later into the spring and summer. That poses a problem to stockmen who typically turn out on summer range in late May and early June, because if elk are still calving in June in the area where cattle are, our risks as livestock people go up. Keeping cattle separated in time and space from wildlife is really important.”
“People cuss Wyoming for having elk feedgrounds, but they do a good job of keeping elk off cattle feedlines,” said Logan of one control strategy. “We all wish they weren’t there, and had never started, because they provide the opportunity for intraspecies transmission in elk, but in absence of feedgrounds we’d have elk all over cattle feedlines and we’d have a much bigger problem with cattle than we do now.”
“Three or four years ago, prior to western Park County being added to the DSA, we had been told the elk in Park County were probably no more infected than about three percent. A year later, we got a report from Game and Fish that they were finding seroprevalence rates on hunter kill and other sampling at nearly 20 percent. In Park County we never would have expected that, because they don’t have feedgrounds. In absence of feedgrounds, how do we keep elk off the cattle feedlines?”
The DSA now includes the western half of Park County, all of Teton and Sublette counties and the northern two-thirds of Lincoln County, and also the area west of the Wind River Indian Reservation in Fremont County.
“I don’t know what the Wyoming Livestock Board (WLSB) will do now that we’ve had the situation in Meeteetse, but we do know there are infected elk east of Highway 120, which is the boundary in Park County,” said Logan. “There is a possibility the WLSB will entertain changing the boundary of the DSA, but I don’t know where that will go yet. The key thing the WLSB needs to consider is making sure we protect all of Wyoming, as well as our trading partners, from buying brucellosis-infected or exposed cattle.”
As a result of the Park County cases in 2010, the WGFD is collecting more slaughter samples in the area and has extended the elk season in the region to move elk away from cattle.
“It may help a little bit, but I’m not sure. If we move elk off one place, they’ll find feed someplace else,” said Logan. “The Game and Fish has been a pretty good partner in alleviating the exposure risks, but my biggest complaint has always been that they’ll give me a figure for their target population in these elk herds, but most are over objective and they’re not doing a great deal to work on them. We can’t do much with this disease without using some of those tools to keep elk away from where cattle are.”
Of the USDA APHIS Brucellosis Interim Rule that’s in the works, Logan said, “This will deviate from the current brucellosis uniform methods and rules in the current code of federal regulations, and I agree with them doing this because both of those documents are very outdated, going back to the 1950s when we were dealing with a nationally infected herd and the focus was cattle to cattle transmission, and we were using strain 19 vaccine. Those situations are no longer relevant.”
Up until late January the GYA had been the only place where brucella abortus was still a problem in the U.S. However, Texas found a case recently in the southern tip of the state from a cowherd that most likely relates to a Mexican import situation, said Logan.
“Now we’re not the only guys playing this game, but we’re still the primary focus,” he added.
In the interim rule the country will be declared free of brucellosis in livestock, and when cases are found in Wyoming, Idaho or Montana, or anyplace else in the country, they’ll be dealt with on an emergency basis.
“That’s nothing different than what we’ve done the last 15 years, with the infected herd quarantined, and contact and adjacent herds quarantined and tested. Nothing will change in Wyoming with this interim rule. Most of what would change is in wildlife arena, where wildlife agencies would have to meet certain criteria, and I don’t know how that will all play out,” he explained.
Logan said he’s formulating comments on the interim rule for the WLSB to review at their meeting Feb. 16. The deadline for comments to be submitted to USDA is Feb. 25.
“We already have a good surveillance and prevention system. We know we’ll find brucellosis occasionally in the DSA. It’s inevitable, and we’ve got too many infected wildlife. The cases we’ve had show me that our surveillance system works, and we caught the disease before it spread, even very much within those herds – at least the cattle herd,” he stated.
“If we continue as we are, Wyoming will maintain brucellosis-free status and should be able to continue to market cattle,” he said.