Brucellosis incidence increases in elk herd in Bighorn Mountains
Worland – At the latest meeting of the Brucellosis Coordination Team on Nov. 12, members of the team looked at the implications of three new seropositive elk that have shown up in the Bighorn Mountains during this year’s hunting season.
“The main topic from that meeting are the seropositive elk we have seen,” said Jim Logan, Wyoming state veterinarian. “How much exposure do we have to brucellosis from the elk? I don’t think anyone can really answer that.”
Logan further noted that surveillance needs for cattle in Big Horn and Sheridan County were also discussed at the meeting.
Brucellosis was first detected in the Bighorn Mountains when two elk were found to be seropositive in 2012. Two more were identified in 2013, and three have been found this year.
“This year, Wyoming Game and Fish Department (WGFD) found one elk in Hunt Area 40, where the previous elk had been found,” Logan said. “They also found one in Hunt Area 39 and Hunt Area 41.”
The two areas are immediately north and south of Hunt Area 40, and Logan commented, “It isn’t a surprise that it is being found in other hunt areas. They were all pretty close to Hunt Area 40.”
For the livestock industry, Logan noted that no cattle surveillance requirements are mandatory at this point, and he said, “I’m not at the point where I would suggest expanding the boundaries of the Designated Surveillance Area (DSA).”
He also said it is premature to even discuss expanding the DSA, but it will be important to monitor the results from the rest of the 2014 hunting season.
“Since we have found elk outside of the DSA to have titers to brucellosis, surveillance has been on a voluntary basis,” Logan continued. “The majority of the samples have come from the Sheridan County side of the Bighorns. We aren’t getting a great cross section of herds or even an adequate number of cows tested.”
Additionally, Logan noted that the majority of cattle tested have been tested at the farm or ranch, rather than at markets.
“The bulk of testing at markets has been done at the Billings, Mont. markets,” he said. “We aren’t getting many tests from our in-state markets.”
Other states have also maintained an interest in the status of brucellosis in Wyoming cattle.
“Other states haven’t threatened to do anything at this stage of the game, but they have a keen interest,” Logan said. “However, if we find one cow outside the DSA with brucellosis, other states are going to start making rules for us. We don’t want that. We should police ourselves as we have in the past instead of leaving it up to 49 other state to impose rules on our producers.”
Logan recommended that producers should take advantage of testing when they are preg-checking cattle. The Wyoming Livestock Board (WLSB) also reimburses the cost of testing in the DSA and approved “areas of concern.”
“Cattle could be tested at pregnancy testing time,” he said. “While it is an added effort, they won’t have to work the cows one more time. We may have missed the window of opportunity this fall, though, as many producers have already pregnancy-tested their cattle.”
He additionally noted that the WLSB has been working to make veterinarians aware of and involved in the importance of testing.
Logan also noted that the WLSB is working to set up meetings with producers to discuss the implications of brucellosis and not testing.
“We want to create awareness on the seriousness of this situation,” he said. “It would be ideal if producers would call us, go through the herd plan risk assessment process and develop a herd plan.”
If producers test early, there is an opportunity to address any potential problems before calving season.
In elk herds
WGFD Wildlife Disease Specialist Hank Edwards commented, “This is awfully tough to really wrap our hands around as to what might be going on. I think we can speculate a lot.”
Edwards noted that, from his viewpoint, the first case in 2012 was regarded as a “flash in the pan.”
“When we came back in 2013 with elevated surveillance, really hit it hard and came up with two more positives in the hunt area, that raised the concern level,” he said. “We now have brucellosis out of the Greater Yellowstone Area (GYA).”
While the appearance of brucellosis outside of the GYA is alarming, Edwards also commented that a silver lining is present in that the WGFD has stepped up their surveillance efforts successfully.
“I think we have a fair handle on where brucellosis occurs in the Bighorns,” he added. “The silver lining here is that all of the positives we have had are on the eastern slope of the Bighorns, and they are all closely clustered. This is a good thing.”
In 2014, 427 useable blood samples were submitted to WGFD, Edwards noted that their samples are a pretty good representation of the elk in the area.
“In some hunt areas, like Hunt Area 38, we are able to a blood sample on every other elk,” he said. “Others we don’t have the same coverage.”
The usability of the samples is also a factor.
“Not all of the samples we get are suitable for testing for a variety of reasons,” Edwards explains. “This year, about 75 percent of our samples have been suitable.”
WGFD Wildlife Management Coordinator Tim Woolley added, “We’ve made some great progress and are getting hundreds of samples back from hunters now.”
Woolley noted that extra efforts have been made to collect blood samples, including increasing WGFD presence in the field and increased contact with hunters during the season. The efforts have increased sample submission dramatically.
Edwards also noted that it is important for surveillance efforts to continue into 2015, particularly on the western side of the Bighorns.
The question that WGFD is seeking to answer is where did the brucellosis come from.
“Are these elk moving in from somewhere, or is this disease becoming established in the Bighorns?” Edwards said. “We would love to know the answer, but it isn’t easy.”
He also noted that obtaining a Brucella isolate would be ideal to help to determine where brucellosis came from.
“Unfortunately, it is super hard to get tissue on hunter harvested elk,” Edwards noted. “The questions we have to answer continue to be tough.”
Human health impacts minimal
Wyoming Game and Fish Department Wildlife Disease Specialist Hank Edwards emphasized that while elk have come back seropositive for brucellosis, it does not necessarily mean the elk have brucellosis.
“Just because an animal is seropositive does not mean that the animal is capable of spreading disease,” Edwards explains. “There is very little threat to hunters and to humans from brucellosis in elk during the fall and early months of winter.”
Edwards explained that as with humans, if elk are exposed to disease, the animal’s body begins to produce antibodies, which can be detected in the bloodstream for a period after exposure to the disease.
“For example, humans continue to hold a titer to diseases like chicken pox, measles and mumps after getting the disease or being vaccinated for it,” he said. “Elk probably don’t hold a titer for as long as humans do, but nonetheless, they hold the antibodies for several years.”
Edwards further noted that brucellosis is very unique in that can be difficult to culture from the animal until the third trimester of pregnancy, when the organism becomes active.
“In the third trimester, Brucella moves into the reproductive tissues and infects the cotyledon, which is where the female uterus is attached to the fetus,” he said. “It destroys the cotyledon and infects the fetus, which causes the fetus to abort.”
Abortions typically occur in February, March and April, leaving hunters at little risk of exposure.
“Most hunters are very safe,” Edwards said. “It is not a disease that affects meat, so the chances of hunters contracting brucellosis is very, very low.”
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.