A suspected deer-to-human tuberculosis outbreak in Michigan’s wildlife disease laboratory may have begun a year earlier than the state had acknowledged, Bridge Magazine has learned.
The timing matters because the state’s failure to initially test one worker means the Department of Natural Resources may have missed an opportunity to identify the contagious respiratory disease before four additional workers tested positive last summer.
The agency now concedes it neglected to conduct a routine screening of a lab technician to ensure this person was TB-free before the deer-hunting season that began in October 2018. This worker could have been infected as early as 2017, the DNR now admits.
“We’re not sure when exposure for this individual might have occurred — it could have been 2017 or 2018,” DNR spokesman Ed Golder told Bridge for this report.
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The admission is a departure from what the DNR said in March, when Bridge first broke the news of the tuberculosis outbreak, and raises fresh questions about the department’s transparency.
The disease lab is housed at the Michigan State University Veterinary Diagnostic Laboratory in East Lansing. Lab workers test thousands of deer annually in search of two challenging illnesses: chronic wasting disease and bovine tuberculosis.
Four of the five workers diagnosed with a latent form of TB last summer were thought to have likely contracted it from examining deer killed by hunters in the 2018 deer hunting season, which ran from the last three months of 2018 into January of 2019.
Records show lab workers were challenged by the volume of deer they were instructed to examine for disease that season. Workers racked up hundreds of hours of overtime looking for chronic wasting disease. More than 35,000 deer were tested from the 2018-19 deer hunting season, about 12,500 more than the year before.
Public health investigators found overflow conditions in the wildlife lab, with legions of deer heads in rows on the floor. They also noted lymph node dissections performed in annex rooms with lower rates of air exchange and without using biosafety cabinets.
Bridge’s earlier investigation, published March 6, found that five of the lab’s 10 workers screened positive last summer for TB, likely acquired during the surge in testing. State job safety regulators launched an investigation into lab conditions three days after the Bridge article.
Bovine TB is found in cattle but also in deer, though transmission from deer to humans has rarely been documented. Latent TB is not infectious to others unless it progresses, as happens in about 10 percent of cases. Treatment is typically necessary, including months of antibiotics, which the DNR said its workers received.
The state agency did not publicly announce the TB infections last year. In fact, records obtained by Bridge suggested the department was keen on keeping the outbreak quiet. One DNR supervisor was threatened with punishment after he told a hunting group about the lab outbreak, according to personnel records obtained under the state Freedom of Information Act.
According to Golder, DNR Director Dan Eichinger decided the privacy of workers’ health conditions outweighed public disclosure because none of the infected workers were considered infectious to others.
“It’s conceivable the increased (deer) volume in 2018 led to human error or some other problem” that infected workers, Golder said in the spring.
But an internal memo recently obtained by Bridge shows the DNR knew then that one of the five workers was likely exposed before the 2018 hunting season, but was not tested.
“This tech did not work in the (wildlife) lab during the 2018 season,” according to a weekly staff update written to the state health director last August. “So a potential occupational exposure would have been prior to 2018.”
Golder told Bridge this memo was inaccurate: The technician did in fact work during the 2018-19 season — but only the first week of the hunting season starting Oct. 1, before leaving DNR.
Even so, state records suggest this worker likely was exposed before that time.
That’s because, as Golder acknowledges, no infected deer were found that first week of October. And there were just a few deer infections in the preceding months of 2018. By contrast, dozens of deer were found the previous testing season in 2017, DNR records show.
Golder defended the agency’s failure to disclose the testing lapse until now.
“We have not said all the infections occurred in the 2018 season, only that this was the most likely time, given the other positive tests (last summer) and a dramatic jump in specimens,” Golder wrote Bridge in an email.
And he dismissed the possibility that DNR’s failure to previously test the worker allowed a dangerous problem to persist. “I’m not certain the conclusion can be drawn there was a ‘significant’ chance of infection prior to 2018,” Golder said.
Baseline testing for possible diseases, common in health care and lab settings, requires personnel be screened at hiring and annually thereafter. This helps to ensure outbreaks are discovered early and limited in time.
Employee lab screenings are generally conducted in the summer, before archery season begins Oct. 1, with the vast majority of hunter-submitted deer specimens arriving between Nov. 15 through the 15-day firearm deer season, which ends Nov. 30.
The lab technician, who the DNR did not identify, was first screened in August 2017 and did not test positive for TB, Golder said. “We know infection for that individual occurred sometime after that, but we don’t know when,” he wrote in an email, underlining the words for emphasis.
“The person wasn’t tested in August 2018 … because of the expectation at the time that the employee would be leaving prior to the start of the 2018 deer season, rather than in October as turned out to be the case,” Golder wrote.
“It was only after we discovered infection at the lab (in June 2019) that the person, who at that point was not working for the DNR, was tested. That was in August 2019.”
Michigan is the only state where bovine TB is endemic in deer, meaning it can survive indefinitely at low levels. Almost all infected deer have come from a four-county area in the northeast Lower Peninsula: Alcona, Alpena, Montmorency and Oscoda.
Transmission of TB from animals to humans is extraordinarily rare. Only three U.S. cases were known, all involving Michigan hunters, the U.S. Centers for Disease Control and Prevention reported last September, before the infection of the five lab workers became public.
“We went back to be certain that in addition to lab staff, other DNR staff who helped at the lab during the period 2015-2017 were also tested,” Golder said.
That’s not accurate, according to biologist Anna Mitterling, who said DNR did not reach out to her to get tested after the lab workers were diagnosed last summer.
Mitterling volunteered during the 2017 season while working for Michigan United Conservation Clubs and wrote about the experience. Mitterling said she first learned of the TB outbreak when told by Bridge in March. She called the lab and was advised she could come in for screening, but COVID-19 closures prevented her from being tested. Mitterling told Bridge in mid-June she still had yet to be screened.
But she said she is unconcerned.
“The possibility is very remote,” Mitterling said. “I didn’t work on any deer from that region. They have different colored tags.”
State tuberculosis and zoonotic disease experts investigating last year’s outbreak identified inadequate storage and safety lapses at the wildlife lab that might have amplified airborne hazards, their July 24 report shows.
“Such excess in testing relative to facility design and the length of duty shifts could result in an increased risk of occupational exposure,” wrote Peter Davidson, TB program manager for the Michigan Department of Health and Human Services.
MDHHS was notified last August about the possible earlier TB exposure of the former worker, department spokesperson Lynn Sutfin told Bridge.
“This new knowledge did not affect the guidance and technical assistance we provided DNR,” Sutfin said.
The state investigation — prompted by Bridge’s reporting — into possible workplace safety violations remains open, said Camara Lewis, spokeswoman for the Michigan Occupational Safety and Health Administration.
The lab controversy is the second in the past year to draw attention to DNR’s reticence to address outside scrutiny.
A Bridge investigation in November showed that DNR leaders improperly blocked the release of public documents that contradicted the department’s rationale for killing federally protected gray wolves in 2016.