Brucellosis discovered in three Madison County cows

During a pre-slaughter test early last month, a cow in a Madison County herd tested as a reactor for brucella bacteria and later tested positive for brucellosis. After further testing, two additional positive cows from the same herd and in the same age range were identified. The cows had all run the same pastures. Because of the index cow’s negative test last year, the cows’ prior pastures can be taken off the table as possible locations of infection.

The index cow, the first to test positive last month, had a clean test July of 2012. Adjacent herds will be tested and about 500 cows in the 1000-head herd that included the infected cow have been tested. It is believed that the cow may have contracted the disease from an infected elk herd. The same day the test came back for the Madison County cow, a positive test came back for a cow in Park County. That cow came from a smaller herd of about 550 and it was determined that the infection was not from intra-herd transfer.

Infected herds are first put under a verbal quarantine and then a written quarantine while testing is done. The same is done with adjacent herds. Herds can come off quarantine in as little as six to seven months, but it could also take longer.

Long quarantines and the resulting limited ability for ranchers to manage their herds had some Madison County ranchers at a meeting in Ennis frustrated last week. Ranchers in attendance nodded in agreement with Benny Clark’s statement that they don’t need to be afraid of or nervous about their neighbors’ cattle, but rather of elk herds that can spread the disease. Montana Department of Livestock personnel told the crowd gathered that folks at the state level are working with and trying to put some pressure on Montana Fish Wildlife & Parks about their management of elk herds in the area.

Non-adjacent herds can and have gone about business as usual. Madison County is part of a four-county surveillance area that has heightened testing requirements. Sanctions were instituted against the state’s cattle producers in previous years due to brucellosis-positive cattle.

Brucellosis was largely eradicated in the country but persists in herds of bison and elk in the Yellowstone area of Montana, Idaho and Wyoming. The disease causes infected animals to suffer miscarriages. Before 2007, Montana had not had an infection in livestock since 1985. Even though bulls do not spread the disease, they are tested in order to shine light on a positive herd.

“We can’t entirely eliminate the risk from the elk herds, but we can limit the economic impacts on producers,” State Veterinarian Marty Zaluski told ranchers last week. “We’ve been lucky because we’ve been good about testing a lot. Folks deserve a pat on the back.”

Just as with criminal investigations, DNA and fingerprints are used to determine whether or not the brucella bacteria came from elk or bison. Test results from the National Veterinary Services Laboratory in Iowa can identify which strain of the bacteria a cow has. Calves between four and 12 months of age can be vaccinated. That vaccine wanes after about three years; therefore, MDOL recommends a three-year vaccination cycle. This vaccination, along with early detection and frequent testing, combine to benefit ranchers.

“Testing only every three years in high risk areas concerns me,” Eric Liska, MDOL brucellosis staff veterinarian, said. He said that he hoped everyone stayed up to date with frequent and necessary testing.

MDOL staff continues to work with ranchers in the area and are available to answer questions at 444-3374.

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