Bovine TB testing of wild deer wraps up after disease found at Michigan cervid farms

Michigan wildlife scientists found 16 white-tailed deer infected with bovine tuberculosis among those submitted by hunters for screening last year, and more may yet be found.

Researchers at the state Department of Natural Resources are now wrapping up the last bovine TB tests on deer heads from the 2021 hunting season, which comes in the wake of the disease recently being found in two cervid farms. Whole-genome DNA sequencing may help regulators track how the bacterial disease spreads, even between wild deer and livestock.

Bovine TB primarily affects cattle but can spread to all mammals, including humans.

Michigan has a long-running bovine TB zone in the northern Lower Peninsula, where infected wild deer are common. The challenge for regulators and farmers has been to keep the sickened free-ranging deer from infecting livestock animals, whether cattle or deer.

State authorities require regular bovine TB screening of cattle herds and other livestock animals. Officials also encourages deer hunters to voluntarily submit deer heads to test for both bovine TB and chronic wasting disease, another infectious disease that can harm wildlife.

Emily Sewell, state DNR wildlife health specialist, said DNA data collected in the project doesn’t provide 100 percent certainty on how bovine TB moves through free-ranging deer, but can be useful for regulators. Genome sequencing is completed for samples from both wildlife and livestock, and she said it can help piece together the puzzle of disease transmission.

Common disease pathways include nose-to-nose contact between wild animals and livestock, or contamination of hay bales or feed piles.

“We have a really great family tree of all the TB – the genomes of all the TB that’s been found in Michigan – and so that helps us understand when we do have a positive cattle herd or a positive cervid facility, we can look and see what that TB is most closely related to,” Sewell said.

Last week, state farm officials announced the discovery of bovine TB in two animals, one at a cervid farm in Alcona County and the other at a similar facility in Sanilac County. The last time authorities found a bovine TB-positive animal at a Michigan cervid farm was in 2009; TB-infected cattle have more recently been found – including a herd in Oscoda County announced this week, the 82nd affected cattle herd in Michigan since 1998.

State agricultural officials said herds at the two affected cervid facilities have not been destroyed, but instead remain under quarantine. Michigan farm regulators are expected to consult with the US Department of Agriculture on response plans for both herds.

Cervids are deer family species, including white-tailed deer, elk, and moose, among other hoofed ruminant animals. Michigan is home to about 350 deer and elk breeding facilities or high-fence hunting ranches for such animals, all regulated under state agriculture laws.

Industry group United Deer Farmers of Michigan reports more than 40 percent of those facilities launched within the last decade. An economic study the group conducted showed deer farming is an $87.5 million industry in Michigan.

Group President Doug Roberts of Davison, Michigan, said they never like to see any type of disease found in the industry’s regulated facilities in Michigan. But he said it’s “not totally a surprise,” given the area at least one of the affected farms was found.

Alcona County is within the state’s core bovine TB zone for wild deer.

“Even though our industry has 10-foot-high fences, we try to maintain our feeders and waters internally away from the perimeter fences, the potential for nose-to-nose contact, or the spread of that disease, even from predator animals is still possible,” he said.

All livestock farmers are encouraged to store animal feed behind a fence or inside a building, feed livestock daily to avoid leftover silage for wild deer to find, and feed and water livestock away from wild de habitat.

Current statistics show most of the wild deer from the 2021 hunting season that so far tested positive for bovine TB came from Alcona County: eight came from Alcona County, four from Alpena County, two from Oscoda County, and one each from Cheboygan and Montmorency counties . More than 11,700 wild deer from last year were tested statewide thus far, records show.

The DNR made drop boxes available across northern Michigan for hunters to submit deer heads for testing. Additionally, Sewell said the DNR started to work with wild game processors in 2020 and expanded that effort last year, which led to an uptick in the number of deer heads being submitted for testing from the TB zone.

State records show at least 702 of the wild deer tested for bovine TB last year were killed under disease control permit kill tags, most from Alpena County. Shooters must apply for such permits and kill tags.

The goal of that deer-culling program is to help control the transmission of TB to livestock.

Such permits may in some cases be used year-round within the five-county core bovine TB zone: Alcona, Alpena, Montmorency, Oscoda, and Presque Isle counties. Kill tags under approved disease control permits may only be used outside of regular hunting season in the surrounding six counties: Cheboygan, Crawford, Iosco, Ogemaw, Otsego, and Roscommon.

The kill tags must be filled during daylight hours and without the use of artificial light, under Michigan’s Wildlife Conservation Order. That differs from a pilot program launched in 2008 to test the impact of unsolicited disease control kill tags sent to livestock farms in the core TB zone, an effort which drew criticism from hunters.

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