AUSTIN, Minnesota (CNN) -- A mysterious nerve disorder that hit some slaughterhouse employees with debilitating symptoms apparently was caused by inhaling a fine mist of pig brain tissue.
Susan Kruse remains unable to work but has felt some relief with immunotherapy treatments and medications.
While eating pig brains isn't dangerous, inhaling fumes from particles of pig brain matter can be, scientists say.
A translator assisting Spanish-speaking patients helped to expose the hidden risk, which prompted the Centers for Disease Control and Prevention to name a new disease and led to changes in how pig brains are harvested.
Susan Kruse is one of the patients who suffered from the disease that's called progressive inflammatory neuropathy, or PIN.
Her quest for health started with bizarre, unexplainable symptoms and took her to nearly 20 doctors.
For more than 15 years, the 37-year-old mother worked a regular shift at Quality Pork Processors in Austin, Minnesota. In her spare time, she renovated her home with her boyfriend, son and stepdaughter.
In November 2006, the symptoms began. First, there were charley horse cramps in her left calf that wouldn't go away. Within days, the debilitating aches moved to her right leg. Within weeks, the tips of her fingers began to go numb.
Soon, the pins and needles spread to her feet.
She couldn't figure out what was happening to her body. She wasn't doing anything differently. She hadn't had any major health problems in the past.
Kruse went to local doctors, but they had never seen anything quite like it.
"I was very scared," she said.
She underwent countless tests and saw almost 20 doctors, but all the diagnoses were hazy -- everything from depression to gallstones.
By February 2007, Kruse could no longer stand for long periods. She had to give up her job at a pork processing plant.
"The doctors couldn't believe how fast it came on. In a four-month period I went from being able to walk to not being able to walk," Kruse said. "I'm only in my middle 30s -- who needs to be in a wheelchair in the middle 30s?"
While Kruse continued to struggle with her illness, something strange was unfolding a few blocks from her home.
At Austin Medical Center, a language interpreter began to notice a pattern.
Over the course of 2007, she found herself translating a similar list of ailments from Spanish-speaking patients to doctors.
She heard the same complaints over and over: aching leg pain; an odd numbness and tingling in the hands, legs and sometimes face; weakness; tiredness.
"There was a group of patients seeing different doctors that all seemed to have a similar set of complaints," said Dr. Daniel Lachance, a neurologist.
At the time, Lachance worked at the Austin Medical Center and the Mayo Clinic in Rochester. He asked Austin doctors to try to refer all the similar cases to him.
By late 2007, his team tracked down 12 people, including Kruse, with similar stories.
"These individuals, one, had a common pattern of illness, but also they had something else in common," Lachance said. "They all appeared to work in the same place, which is Quality Pork Processors in Austin."
But the similarities didn't end there.
"When we looked a little further, it seemed that these workers were clustered in a particular part of the plant," according to Dr. Ruth Lynfield, a leading epidemiologist at the Minnesota Department of Health.
Lynfield surveyed the plant with QPP President Kelly Wadding. They focused on a section of the plant called the "head table," the area where brain tissue was harvested and packaged for export.
The market for pig brain tissue includes the American South, where it's used in dishes such as brains and eggs. It's also sold in some Asian countries, such as Cambodia and China, for various recipes, including stir-fries and stews. The brain tissue processed at QPP was used mainly for export to Asia.
State and federal health authorities have said eating pork brains is safe. It's the harvesting method, called "blowing brains," that posed the health risk.
In the procedure, high blasts of compressed air were shot into the head cavity to remove the brains. Sometimes the liquid combined with brain tissue and turned into a mist.
Health investigators said droplets of the mist could have entered a worker's system through the mucous membranes in the nose or mouth. Once in the body, the foreign pig brain matter prompted the immune system to produce antibodies to attack it, in a process similar to an allergic reaction.
But the foreign matter seems to have also triggered an attack on the body's nerve tissue, killing some of the nerves and causing the mysterious numbness.
On January 31, the CDC gave a new name to the unique constellation of ailments: progressive inflammatory neuropathy, or PIN.
"The pattern of abnormalities falls into a combination that we really have not seen with other illnesses," Lachance said.
He is helping to investigate whether PIN cases went unreported or undetected before late 2006.
The CDC also is tracking two other plants that used the procedure. At one plant in Indiana, there have been three confirmed cases. There have been no cases confirmed at a Nebraska plant.
Pig brains are no longer harvested with compressed air. Health authorities have said swift action by QPP management were key to containing the outbreak.
Wadding, who has been QPP president since 1997, said, "Since we put in some precautionary measures and stopped harvesting brains, we have not had any new cases."
To date, no one has died and most patients have recovered and returned to work.
Kruse remains unable to work, but she said she has felt some relief with immunotherapy treatments and medications.
While health authorities are convinced the outbreak is contained, they said it will take months, perhaps years, to understand fully what caused or triggered the illness in workers. E-mail to a friend
A. Chris Gajilan is a senior producer with CNN Medical News.
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