A 12th worker at a pork processing plant in Austin, Minn., appears to have the same mysterious neurological condition identified in 11 others by an ongoing state health department disease investigation.
But health officials have backed away from their earlier identification of the condition as chronic inflammatory demyelinating polyneuropathy, or CIDP. Initially they said that five of the workers had CIDP. After additional testing, officials said that none of the workers fits the precise diagnosis of that extremely rare disease -- though the tingling and numbness they experience in their arms and legs are similar to it.
Officials believe the condition is causing the workers neurological problems but at this point it cannot be identified as a known or specific disease.
Last week the Minnesota Department of Health announced it had launched an investigation into a cluster of illnesses in 11 workers at Quality Pork Processors in Austin.
They all worked in the same area -- the head table, where workers cut the meat from pig heads and extruded the brain from the skulls with a compressed air system.
Though health officials are looking into all possible causes of the illness, they have focused on the compressed air system, which is used by only a few meat processing plants in the country. The system, which exposes workers to airborne particles of pig blood, tissue and fluids, was implemented around the same time that the workers first started reporting problems last December. The plant has stopped using it and now provides employees with more protective clothing and face masks.
Dr. Daniel Lachance, a neurologist at the Mayo Clinic who is involved in screening the workers, said that preliminary tests conducted last week on the 12th worker indicate she has the same symptoms as the others. She worked in the area under investigation. The evaluation is not yet complete, "but I'm convinced that she has it," he said. "The preliminary testing is consistent" with the others.
Ruth Lynfield, the state epidemiologist, said that she is not surprised that an additional case turned up and that investigators may yet find even more at the Austin plant or at others. They spent last week talking to hundreds of plant workers and anyone who reported neurological symptoms was referred to the Mayo Clinic for screening. Lachance said that a 13th worker is also going through the evaluation process, but preliminary results are not yet available.
A less-specific diagnosis
Lachance and Lynfield also said that further testing has shown that the workers do not have CIDP, a disease in which the immune system for some unknown reason attacks the protective sheath that surrounds nerves. CIDP is very rare, occurring in about 2 out of 100,000 people, and can often be disabling.
Key to differentiating the condition from CIDP is a characteristic of CIDP involving an interruption or blockage of the electrical signaling in and between nerves, Lachance said. Tests now show that none of the 11 workers has that problem, he said.
They do have damage to the nerve system caused by their immune systems, he said. But at this point it can be categorized generically only as an inflammatory response that is damaging the nerve sheaths, he said.
Two of the 11 have symptoms that are different than the rest, Lachance said. One has problems in the spinal cord, and the other has problems in muscles. The others have symptoms that are more similar, characterized by tingling, numbness, discomfort in arms and legs, and variable amounts of weakness. They also described "a very abrupt sense of fatigue," he said.
For example, one worker was a regular soccer player until he started experiencing tingling and numbness in his legs. Now he can't play and even walking up stairs is exhausting, Lachance said.
Mayo doctors are developing a treatment regimen for the workers, he said. Most have not been completely evaluated for treatment, but he expects that with help most will improve.
"If we never exactly figure it out and patients stop getting sick, that's good," he said. "We're happy with that."
Josephine Marcotty • 612-673-7394