Case of TB in cattle prompts deer testing

By Tim
Spielman

Associate Editor

St. Paul – The discovery of bovine tuberculosis in a cattle herd
in northwestern Minnesota has prompted the state DNR to announce
deer testing will take place in Roseau County this fall to see if
area whitetails contracted the respiratory disease.

Mike DonCarlos, DNR wildlife program manager, said the exact
area and the target number of deer to be tested hadn’t yet been
determined.

“What’s clear is our goal – to determine if it’s been
transmitted to white-tailed deer, and if it has, how far it’s gone
and the infection rate,” he said. “The first step is to find it, to
determine if it has or has not gotten into the deer herd.”

DonCarlos said bovine TB is a contagious bacterial disease
that’s found in cattle, but can be transmitted to other mammals,
including deer and humans. It’s a chronic, slowly spreading disease
that doesn’t spread easily. Bovine TB has never in the past been
found in Minnesota deer.

Interaction between deer and cattle on the 5,000-acre cattle
farm likely occurred, he said. Whether the disease was transmitted
or not must be determined.

The cost of testing is unknown, DonCarlos said, because the
agency hasn’t decided what type of test will be performed and how
many animals will be tested. Funding will come from a DNR account
dedicated for wildlife health issues – the same fund that provided
money for chronic wasting disease testing the past few years.

“We don’t expect it (TB testing) to be costly, and the money is
there,” DonCarlos said.

The testing won’t occur on the scale of that done for chronic
wasting disease during the past few years. The DNR’s Jason Abraham
said since 2002, about 28,000 deer have been tested for CWD in all
areas of the state. None have tested positive.

According to the DNR, bovine TB has been a rare occurrence in
white-tailed deer and hasn’t persisted in wild deer populations.
Prior to 1994, only eight cases had been documented in wild deer in
North America. However, since that time the disease has persisted
in deer in several Michigan counties, possibly due to high deer
densities and the prevalence of artificial feeding, the DNR’s press
release states.

The DNR recommends hunters and others follow a few simple rules
regarding disease in wild animals.

“Baiting and feeding concentrate wild deer, which may increase
the spread of diseases, such as bovine tuberculosis,” DonCarlos
said in a DNR statement. “Baiting is illegal in Minnesota, and the
DNR discourages placing feed for wild animals.”

Thorough cooking of the meat destroys the bacteria. Hunters
should use gloves when field dressing deer to prevent disease
exposure.

“This shouldn’t change anyone’s plans to hunt deer in
northwestern Minnesota this fall,” DonCarlos said. “With the proper
precautions, hunters can safely field dress and enjoy their
venison.”

The Michigan experience

The area of concern in Michigan has been a four- to five-county
area in the northeastern Lower Peninsula. Bovine TB was discovered
in deer there 10 years ago, and testing of deer and liberal harvest
continue today, though testing in 2004 showed “much progress had
been made toward eradication of bovine TB in the wildlife
population,” according to the Michigan DNR.

The Michigan department tested more than 15,000 hunter-harvested
deer last year, and 28 animals turned up bovine TB-positive. The
prevalence rate in Deer Management Unit 452 – the area hit hardest
by bovine TB – was 1.7 percent, a decrease of 65 percent since
1995.

The DNR in Michigan also is working to develop an accurate TB
blood test and an effective TB vaccine, the agency states in a news
release.

“Clearly, we are winning important battles in the war on bovine
TB,” said Stephen Schmitt, a Michigan DNR official.

Bill Parker, editor of Michigan Outdoor News, ON’s sister
publication, said the TB “scare” first hit the state hard, but
currently CWD causes more concern, even though that disease hasn’t
been found in the state’s wild deer herd.

“It was the first big scare, a really big thing that affected
hunting,” he said of TB. The discovery of TB led to the prohibition
of baiting in the TB core area (baiting is illegal in Minnesota)
and restrictions outside that area.

Also, the DNR in Michigan has been offering over-the-counter
sales of deer tags to aggressively reduce the herd size in that
area, Parker said. The department believes it has reduced the deer
herd by 50 percent; some hunters in the area believe the herd’s
been reduced even more than that, he said.

Currently, he said the department’s plan is to “stay the course”
by continuing to put harvest pressure on the herd and keeping bait
out of the picture. The rationale is that baiting and feeding
concentrate deer, making nose-to-nose contact more likely and
increasing the chances of disease spread.

Parker said the prevalence rate has dropped from a high of more
than 5 percent testing positive for TB in the core area to less
than 2 percent. In the outlying area, the prevalence rate has
decreased from just over 2 percent to less than 1 percent.

“There’s more concern now about CWD, and we don’t even have
that, that we know of,” he said.

The Roseau herd

Not since the 1970s has the state had a case of bovine TB in a
cattle herd. At that time, the state had to be “TB-free” for five
years to be considered free of the disease by the U.S. Department
of Agriculture, said Malissa Fritz, communications director for the
state Board of Animal Health. That status returned in 1976.

But earlier this month, a USDA veterinarian detected suspicious
lesions in a 5-year-old cow during routine slaughter surveillance.
The cow was traced back to northern Minnesota using a “back tag”
placed on the cow prior to being sold for slaughter. The Rouseau
County herd, which numbered nearly 1,000 animals, was quarantined,
tested, and an investigation initiated, according to the BAH.

Fritz said officials conducted a “whole-herd” test, which
included 568 animals from the Roseau herd. Of those tested,
biologists were particularly interested in the results from 21 of
them, she said. Those were tested at the University of Minnesota
Diagnostics Laboratory, and 18 tested positive for bovine TB.

“That number told us we had an infected herd,” Fritz said.

Once the USDA and the producer work out an agreeable price
during the indemnity process, the herd will be “depopulated,” she
said. Currently, state and federal officials are investigating
where the cattle from the Roseau herd came from, and perhaps where
they’ve gone. Further, three herds that had “fence line” contact
with the infected herd also will be “whole-herd” tested for the
disease.

Officials also are now discussing how long it will be before the
Roseau farm is “cleared” – when they believe the bacteria has been
eliminated from the farm site.

Categories: Hunting News

Leave a Reply

Your email address will not be published. Required fields are marked *