Disease focus Team looks at brucellosis challengesWritten by Saige Albert & Joy Ufford
Pinedale – As brucellosis continues to challenge western Wyoming ranchers, the Brucellosis Coordination Team (BCT) met on April 15 to look at actions that can be taken to continue to combat the disease.
“It was a good meeting, and there was a good turnout,” said Wyoming State Veterinarian Jim Logan following the meeting.
The day brought talk of affected elk in the Bighorn Mountains, a National Academy of Sciences’ (NAS) upcoming special report, possible renewal of local test-and-slaughter programs and genomic research that models the “origin” of Greater Yellowstone Area (GYA) brucellosis back to elk and the Jackson Hole area.
The disease is not widespread but is mainly found in Idaho, Montana and Wyoming around Yellowstone, where the designated surveillance area (DSA) imposes different rules on cattle transfer. Affected cattle and domestic bison herds are quarantined, and adjacent herds are tested to contain its spread among breeding livestock.
The BCT includes members of the University of Wyoming (UW), Wyoming Game and Fish Department (WGFD), Wyoming Livestock Board (WSLB), legislators, ranchers, outfitters, sportsmen and federal agencies.
One topic of conversation during the meeting was a proposal to remove Brucella abortus – the pathogen responsible for causing brucellosis – from the Select Agent list. Three Brucella bacteria are considered “select agents” by Homeland Security – Brucella abortus, Brucella melitensis and Brucella suis – due to their potential to be developed as bioterrorism agents with the ability to be aerosolized.
“We talked about submitting comments from the committee on a proposal by USDA and Homeland Security about removing these agents from the list,” said Logan.
Because B. abortus is currently on the Select Agent list, research is limited, and the delisting proposal would be monumental for brucellosis research.
“Delisting B. abortus would enable research to be done on a bigger scale with more animals,” Logan explained, noting that currently research can only be done in Bio-Safety Level (BSL)-3 or BSL-4 laboratories. “In these BSL-3 and BSL-4 labs, there isn’t room to have more than a few animals, and it doesn’t do as much good if we only have a couple.”
Additionally, if B. abortus is delisted, challenge studies would be possible.
“There are some big implications if they delist it,” he added.
The comment period on the action ends April 28.
Peggy Yih and Robin Schoen of the NAS, in Washington, D.C., also attended the meeting to get a grasp on brucellosis activities, programs and reports after the USDA Animal and Plant Health and Inspection Service requested an updated brucellosis review.
APHIS requested a review of new materials and actions with the National Research Council’s (NRC) 1998 report as the foundation, Yih explained. Its working title is “Brucellosis in the Greater Yellowstone Area.” Its statement of task is to get up-to-date literature and expert input, so NRC experts can recommend best options for dealing with brucellosis, based on scientific evidence.
“Some of the literature is quite old,” BCT Director Frank Galey said. “I am hopeful this committee has the time and resources to dig deep and be critical.”
The NRC has received nominations of more than 100 people to serve on the review committee, based on their individual areas of expertise and experience, Yih added. The final nominations will be submitted and checked for conflicts of interest before the NRC approves them to be seated on the committee.
That will open a 20-day comment period. The committee will be provisionally seated and vetted one more time at its first meeting in late June or early July. Three more meetings will follow through 2015 and early 2016, and all will have open public and closed working sessions, according to Yih.
After a report is written, it will be reviewed by peers and an NRC panel, which will sign off on it and submit to the NAS for approval, Yih and Schoen explained. That’s when it becomes public.
Sublette County Rancher Albert Sommers said, “This report will be done, but I hope this will help and not hinder what’s already on the ground.”
Also as a highlight of the meeting, Pauline Kamath presented her preliminary findings of a GYA genomic study of brucellosis transmission for the U.S. Geological Survey (USGS).
Brucellosis is simpler to track than many bacteria because it has low genetic diversity, she explained, and with 250 whole genome sequences from GYA cattle, bison and elk over 48 years, the study modeled brucellosis transmission across space and time.
The same technique is used to track anthrax and the SARS virus, Kamath said.
“It is pretty powerful to have that many genomes,” she said, adding the data could model the spatial distribution of all brucellosis ‘lineages,’ how they cluster and how they relate to one another within and outside the GYA.
“There are similar relationships among the brucellosis cases, and they share a common ‘ancestor’ in the past,” Kamath said.
The models show a linear “ancestor” was a host 30 to 50 years ago, that through transmission, had created five genetically established “lineages” that “all go back to the late 1700s,” she said.
That conclusion is determined by working backward with models of host species and genomic data, she explained.
Lineage and movement
One line of brucellosis moved west to Idaho via elk feedgrounds, and another appeared in Yellowstone and Paradise Valley. Two more widespread lineages “possibly have been around longer or have spread more effectively,” she said.
The fifth and probable originating “ancestor” came from the National Elk Refuge in Jackson and spread southwest to WGFD elk feedgrounds, Kamath explained. Cattle there likely received brucellosis from wildlife.
She suspects, “The primary ancestor would be cattle.”
“Wildlife has been the reservoir source for the last 50 years or so,” she concluded. “The linkages are from the National Elk Refuge area and the Teton area, there’s a lot going on at feedgrounds. For Wyoming, that seems to be a significant factor.”
Wyoming State Veterinarian Jim Logan said an ongoing case of brucellosis in Park County involving a domestic bison herd is on the verge of “testing out” of quarantine.
“I think we’re going to get there,” Logan said. “We need three negative consecutive herd tests, and we have two. We should be able to get that herd off quarantine in 2016.”
A Park County, Wyo. and Carbon County, Mont. cattle herd had an un-bred cow test positive in late October as well, with four adjacent Park County herds and four in Carbon County of 1,700 total being tested, Logan said.
In 2012, the Wyoming Livestock Board issued a voluntary surveillance program in Big Horn and Sheridan Counties after several elk hunted on the west side of the Bighorns tested positive for brucellosis. Wyoming Game and Fish Department biologists in that area propose a study to fit nearby elk with GPS collars to learn where they migrate to keep brucellosis from spreading to beef cattle herds. The two counties have an estimated total of 67,000 cattle between them.
Montana’s Eric Liska, the Department of Livestock’s brucellosis program veterinarian, gave an update on two Montana herds with cattle testing positive last year. One was a single cow in a herd of 2,300. That herd summers with 18,500 more cattle in five Montana grazing associations, and all have been tested twice, he said.
Another herd’s positive reactor resulted in testing almost 21,000 head common to two grazing associations getting tested twice, he said.
“It’s expensive,” Liska said, “but it’s necessary.”
In Idaho in 2012, a recently assembled bison herd in Bonneville County had one animal of 280 reported positive. Further tests showed three reactors. That herd tested out of quarantine last fall. In Madison County, a small beef herd that summers in Fremont County had a cow test as a reactor in 2012, and that herd’s final test will be mid-May. If all test negative, that herd will come off quarantine as well.
Both herds are believed to have mingled with transient elk the previous summer.