She had worked at the Quality Pork Processors plant in Austin for 15 years. Then the 36-year-old started having cramps in her legs, followed by muscle stiffness, soreness and pain that left her unable to work and dependent on a walker to get around.

Kruse was among the first of 11 employees at the plant to be diagnosed with a rare neurological disease called CIPD, short for chronic inflammatory demyelinating polyneuropathy.

Doctors have told her she may never work again. Her disability insurance payments recently ended, and she's now living on Social Security.

``It started with a charley horse in my calf that wouldn't go away,'' Kruse told the Star Tribune in an interview at her home Tuesday night. ``Then my hands and feet got sore and cold and numb. I had perfect health before.''

``She can't do a lot of the things she used to,'' said her son, Travis Kruse, a ninth-grader. ``Before, she could lift heavy boxes and stuff, but now she gets tired after she walks a little.''

The plant owner, Kelly Wadding, said Tuesday that investigators told him they probably won't know ``for some time'' what caused the illnesses.

The Minnesota Department of Health, which disclosed the illnesses Monday, is leading the investigation, which is expected to take months or longer. Department staffers arrived in Austin on Tuesday, while another team is researching the autoimmune disease, which normally strikes only two out of every 100,000 people.

``We're trying to get a sense of whether the incidence has changed in recent years,'' State Epidemiologist Ruth Lynfield said, adding that there could be clusters of cases elsewhere in the country that have not been recognized.

Officials were able to connect the 11 Austin cases because of a fortunate confluence of events, Lynfield said. Plant nurses were the first to recognize that they were seeing an unusual number of people with odd neurological symptoms. They very quickly connected with doctors at the Mayo Clinic in Rochester who happen to be among the nation's experts in CIDP, she said.

Autoimmune diseases occur when the body's immune system attacks healthy tissue because it can't tell the difference between healthy tissue and foreign invaders. In the case of CIPD, it gradually damages the tissue sheath surrounding nerves in arms, legs and the trunk.

Kruse went through another battery of tests at Mayo on Tuesday. Every other week, she spends five hours receiving an intravenous drug that doctors hope will ease her symptoms, which include muscle weakness, pain and tingling. She had been puzzled about the illness until last week, when someone from the Health Department called asking questions. Then she ran into a co-worker at Mayo who had the same illness.

But it wasn't until Monday's Health Department news conference that she realized the link to her job.

Kruse worked in the ``day kill area,'' where she carved meat out of the back of butchered pigs' heads with a small knife. Her work area was next to the place where compressed-air hoses were used to blow out brain material from pig skulls.

According to experts, the cause of CIDP is unknown and could include any number of factors, including infectious microbes, toxins or something from the pigs that triggers the body's immune system to attack healthy tissue. It's the chronic form of another disease, Guillain-Barre syndrome, which develops much more rapidly and has a number of known triggers. It first received public attention in 1976 when linked to the swine flu vaccine. CIDP does not appear to be spread by person-to-person contact, Lynfield said.

Symptoms first emerged around the same time the plant began using the high-pressure air system. Some health experts think exposure to blood and pulverized tissue might have caused the autoimmune response, and they recommended that the plant shut the compressed-air system down.

Kruse said she liked her job and is sorry she can no longer do it.

``It's depressing,'' she said of her increased weakness and decreased mobility and of her uncertain future. ``I hope that my arms aren't so weak that I can't at least get a desk job.''

Update presented on disease in pork plant workers

SEATTLE – More than a year after developing a unique neurological disorder, the affected pork processing plant workers have improved, but all have some continuing symptoms and many have ongoing mild pain, according to a study released today that will be presented at the American Academy of Neurology's 61st Annual Meeting in Seattle, April 25 to May 2, 2009.

The workers developed symptoms such as walking difficulties, weakness, numbness and tingling in the arms and legs, pain and fatigue. All had worked in or near the area where compressed air was used to extract pig brains. All plants have discontinued the practice.

For the study, researchers reexamined 24 of the workers affected at plants in Minnesota and Indiana. Of those, 17 were treated with immune therapy such as steroids. Sixteen people improved with treatment; 12 had marked improvement, two had moderate improvement and two had mild improvement. Six of the people who had no treatment also improved after they were no longer exposed to the pig brain mist.

Neurologists have identified the illness as a new disorder that is a sensory predominant polyradiculoneuropathy. The patients all have a unique antibody not seen before. The disease affects the nerves, and can usually be identified by standard tests (nerve conduction studies and EMG), although in four mild cases specialized tests were needed to detect the abnormalities. The disease seems to improve with treatment and removal of exposure to pig brain.

The disorder likely has an autoimmune basis, with workers exposed to the pig brains developing an autoimmune response that caused nerve damage. The researchers hope that further studies on this disease will aid understanding of other autoimmune disorders. "There are other autoimmune disorders where the trigger is not known, so this case with a known trigger could provide us with an opportunity to understand how an antigen can trigger the body's immune system to produce disease," said study author P. James B. Dyck, MD, of the Mayo Clinic in Rochester, MN, and a Fellow of the American Academy of Neurology.

Additional details on the patients' testing and outcomes will be presented at the AAN Annual Meeting.

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Pork plant worker says symptoms started with charley horse

Update presented on disease in pork plant workers