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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