Doctors still learning from pig brain disorder

By Julie Steenhuysen

CHICAGO (Reuters) - It started with tingling in the fingers and toes, followed by weakness in the legs.

"It wasn't a normal neurologic illness," said Dr. Aaron DeVries, an epidemiologist with the Minnesota Department of Health who helped lead the state's investigation of a mysterious condition that sickened 18 workers at a Southern Minnesota pork processing plant.

Now, more than a year after their symptoms started, the workers are responding to treatment for the nerve illness that is teaching doctors new lessons about autoimmune disease.

DeVries got involved after a cluster of workers at Quality Pork Producers Inc in Austin, Minnesota, became too weak to visit the fourth-floor health clinic, leading the plant's nurse to alert health authorities.

"The most common denominator was people saying, 'We can't make it up the stairs,'" he said.

Most had been assigned to the head table, where they used compressed air to blow the brains out of pig skulls.

"We observed how brain material was both splattered around on other machines and other workers close by," DeVries said. "But there was also smaller material that remained in the air."

It turns out that all of the sickened workers had been exposed in some way to a fine mist of pig brain matter that triggered a new type of autoimmune disease.

In the 15 months since their illness was first reported, all have responded to immune therapy but they continue to have symptoms and many have mild pain.

'EXPERIMENT OF NATURE'

"This whole thing was a man-made experiment of nature," said Dr. Daniel Lachance of the Mayo Clinic in Rochester, Minnesota, who will present his latest findings on the pork workers' disease at a neurology meeting next month.

"It presents an opportunity to understand a phenomenon that is potentially important to all of us -- autoimmune disease," Lachance said in a telephone interview.

Lachance and Dr. James Dyck of Mayo worked closely with health department doctors to learn as much as possible about what made the workers sick.

While they now believe it was an autoimmune response, it took scores of interviews with plant workers, numerous tests and months of observations to make that call.

They considered infectious agents such as prions -- proteins known to wreak havoc on the brain in diseases such as mad cow and Creutzfeldt-Jakob disease.