Wyoming is keeping an eye on Brucellosis
June 24, 2013
Often called Bang's disease, Brucellosis affected as many as 25 percent of cattle in the U.S. before control programs and vaccination. A rigorous program to eliminate this disease in cattle was begun as soon as a vaccine was developed. Vaccination is not 100 percent effective, however, so a test and slaughter program was also used. Herd testing, slaughter of all infected animals, and vaccination of all healthy heifers eventually eradicated this disease in most of the U.S. except where wildlife (mainly elk and bison) continue to pose a threat.
This is a challenge for Idaho, Montana and Wyoming – bordering Yellowstone Park – where the disease exists in elk and bison in the Greater Yellowstone Area (GYA). Dr. Jim Logan, Wyoming State Veterinarian, says these states have designated surveillance areas. "These are the areas where we recognize that this disease is in wildlife, and where all three states have had cases the past dozen years. We have all developed rules for livestock that include surveillance testing and vaccination, and identification to help prevent the disease, and assist in epidemiologic investigations for disease control if it happens," he says.
"In Wyoming we went brucellosis class free in 1985. We did not find another case until 1988 – when one case was found near Dubois, Wyoming, in Fremont County. That case went into litigation, and the cause was ultimately determined to be infected elk in that area. At that time, the affected cattle herd was depopulated," says Logan.
In the late 1990s, due to pressure from other states that received Wyoming cattle, and pressure from USDA-APHIS, the Wyoming Livestock Board implemented test requirement on six counties in northwestern Wyoming (Lincoln, Sublette, Teton, Park, Hot Springs and Fremont counties). That requirement stated that any cattle changing ownership had to be tested within 30 days prior to change of ownership. They were also tested if they went through a Wyoming livestock auction market.
"We did that from 1998 until 2001, at which time we had tested several hundred thousand head of cattle from that area and found no brucellosis. After pressure from livestock owners in those six counties, the Wyoming Livestock Board gave up the testing. We then had voluntary testing, which equated to zero. The only testing done during that time was at slaughter," Logan says.
"From 1988 until 2003, Wyoming did not find another case of brucellosis within our boundaries. Then we found a case in Sublette County, just south of Yellowstone Park and south of Teton National Park, in November 2003. Those cattle were culled from the ranch of origin and sold to slaughter buyers, and when tested at slaughter they were found to be positive. The rancher did not know it was in the herd," Logan said.
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"That herd was quarantined and depopulated – about 400 cattle – at significant expense to the owner. They were indemnified at that time by USDA-APHIS, but even though the rancher was compensated for the cattle, it didn't cover the entire loss. Indemnity payments never do," he explained. The many years of genetic selection, for instance, are gone.
"In the spring of 2004 we found three additional cases in Teton County. At that time, the federal program for brucellosis (which was subsequently changed) required that any state having two or more cases within a 2-year period would lose their brucellosis class free status. This is very important because it impacts freedom of marketability and ability to send cattle to other states without having to test. Wyoming lost its brucellosis free status in 2004, and regained it in 2006 because we didn't find any more cases after we got those herds cleaned up," recalled Logan.
Then in 2008, another case was found. "That resulted in depopulation of a herd of more than 600 cattle. When we find cases, it also involves quarantine of any co-mingled or adjacent contact herds. With the 2003 cases, we had 12 additional herds that were quarantined until they could be tested and determined that they did not have the disease. All of our cases have been contained within a single herd; there has not been any inter-herd spread. All cases in Wyoming, Idaho and Montana in the last 15 years have been determined to be caused by elk, rather than by other cattle."
Wyoming regained brucellosis-free status in 2006 and some changes occurred in the federal program after that. "State Veterinarians from Idaho, Wyoming and Montana and the cattle industries from these states were instrumental in getting APHIS to change some of the protocols in the national programs, one of which was loss of free status. We were depopulating too many herds, APHIS was spending too much money wiping them out, and it wasn't making sense, especially when spread of the disease wasn't from cattle to cattle but from wildlife to cattle," says Logan.
"One change was that even if a state found more than one case within a 2-year time frame, they would not lose their brucellosis-free status as long as they were doing an adequate job (in the eyes of APHIS and other states) of containing the disease and not allowing it to spread from herd to herd. This change helped our states and producers maintain marketability. The second thing was that we went away from whole herd depopulation to a test-and-remove program," he said.
It's not always feasible to test and remove, however. Some herds are so heavily infected that every time they are tested more positives are found. "In order to release the quarantine, a herd must have three consecutive negative whole-herd tests, with the last test at calving season. This is the best opportunity to find the bacteria in blood tests," he explained.
"We made the changes in the federal program, then a case was found in Montana, and one in Idaho. In late 2010 Wyoming had two cases, and two more in 2011. We didn't lose our free status because we contained it to those herds. There was no epidemiologic link between any of those herds – no inter-herd spread. All of the herds adjacent or co-mingled tested negative. So we didn't lose free status. I'm sure it raised eyebrows in other states, but nobody put sanctions on us," Logan said.
"It has been a lot of work to get those herds cleaned up, but we didn't have to depopulate any of those herds and were able to test out of it. This salvaged the herd genetics and made the producers somewhat less frustrated.
"It's no fun to be under quarantine and it isn't fun for me to have to put somebody under quarantine. But we do that to protect the entire state's industry and that producer. My first goal when I put them under quarantine is to devise a way to help them get out of that quarantine and resume business as usual," he said.
All of the cases in Wyoming have been found to be caused by elk transmitting the disease to cattle. "On March 7th I was notified by Wyoming Game and Fish Department that two elk just outside our designated surveillance area boundaries to the east were found positive through our hunter-killed surveillance, which our Game and Fish Department does every year," he explained.
"Those two elk were positive on serology. We don't know for sure if it was actually brucellosis; it's remotely possible it could be cross-reaction from other bacteria, but until we get more elk surveillance (by Game and Fish, in conjunction with Wyoming Livestock Board and producers), we won't know for sure," he said.
"We are working on getting more elk surveillance and cattle surveillance – which will primarily occur this fall at preg-testing time in the cattle herds. We will also get surveillance testing done on any cattle that leave the area of concern. Wyoming is taking steps to try to determine the extent and if it is in fact brucellosis or something else. We hope to know, later this year," said Logan.
"The reason a brucellosis program was started in the 1940s was because of public health significance. We don't see it in humans much anymore, due to milk pasteurization and other strategies, but there is still risk. Many veterinarians and ranchers have been exposed and suffered the consequences, and I am one of those veterinarians."
Whenever there is a case, meetings are held with producers, especially those who will be quarantined, and public meetings to help explain the disease. "When we get a case and implement a quarantine there is a period of panic and public misperception. So we try to explain the impacts. We had a couple recent meetings, relative to the elk situation outside of our DSA. We held one in Greybull on April 4th with producers and public. We had a second meeting at Sheridan, and it was well attended by producers, with a lot of good questions. We'll have additional meetings, probably in June, in Lovell and some follow-up meetings in that area as we find out what the Livestock Board and Game and Fish is going to do regarding surveillance," Logan said.
Editor's note: The Wyoming State Veterinarian with the advisory of the Wyoming Livestock Board has suggested that ranchers around the area where the two elk were discovered, test their cull cows for the reassurance that Wyoming cattle herds are Brucellosis-free.