Twelve of 100 cow elk captured in early February in the Ruby Valley have tested positive for exposure to brucellosis in an initial screening.
“I thought maybe we would get a few, but not that many,” said Neil Anderson, the Fish, Wildlife and Parks wildlife laboratory supervisor who is in charge of the study.
The elk were captured west of the Gravelly Mountains near the Blacktail Wildlife Management Area over four days with the help of a helicopter netting crew. The capture and blood testing is part of a five-year study to help refine the state’s approach to managing the risk brucellosis-exposed elk pose to livestock and focuses on fringe areas of previous brucellosis surveys.
The initial blood testing indicates if an animal has been exposed to the disease and does not mean the animal is infected and can spread the disease, Anderson explained. The cow elk that tested positive in the field and that were pregnant were given tracking devices that will be expelled when they give birth. It’s believed that birth material is the most common means of transmitting brucellosis.
After being tested in the field, all of the blood samples were sent to the Montana Department of Livestock Diagnostic Laboratory for further testing.
Eight cow elk tested positive for exposure in the field, six of which were pregnant and received the tracking device. The Livestock Department lab was where the additional four positives were discovered.
The samples that tested positive on the full panel of tests at the Livestock Department lab will now be sent to a laboratory at Louisiana State University for an additional test to determine if false positive results may have occurred.
Anderson said sometimes the Livestock Department tests will show a false positive from a bacteria that is similar to brucellosis.
“The hard part is sorting out the false positives,” Anderson said.
Actual brucellosis exposure is expected to be somewhere between eight and 12 cow elk, Anderson said.
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“We know the (DOL) test isn’t perfect,” he said. “The Western blot test (at LSU) will reduce it somewhat.”
Results from the LSU laboratory are not expected for a month or more.
“It’s unfortunate that the preliminary results indicate some brucellosis exposure in elk in this area,” said Marty Zaluski, state veterinarian.
In order to better understand elk movements and distribution in relation to the risk of disease transmission, researchers are following 30 GPS radio-collared elk throughout the year to determine seasonal movement patterns and interactions with other elk and livestock. Anderson said that involves about two aerial flights a month plus weekly on-the-ground surveys.
Elk that test and remain positive for exposure to brucellosis for five years will be removed from the population for further study to confirm brucellosis infection.
“The study will attempt to determine if a brucellosis-positive cow elk aborts and if a cow elk that aborts in one year continues to do so, or if it occurs primarily with the first pregnancy,” Ken McDonald, FWP Wildlife Bureau chief, said in a statement. “In addition, the study will attempt to determine if elk that test positive in one year continue to do so in succeeding years.”
Over the course of five years, crews will capture 100 elk in a different area each year. The effort will be replicated in four other areas between 2012 and 2015 if sufficient funding and collaboration with landowners can be secured. The study is estimated to cost about $300,000 each year.
“We’re hoping the information we get from this will improve our understanding of seroprevalence and what it means,” Anderson said.
Contact Brett French, Gazette Outdoors editor, at email@example.com or at 657-1387.