"We are very worried about the situation," said Dr. Julie Gerberding, head of the Centers for Disease Control and Prevention. "This is a pretty serious and progressive nerve disorder."
But there is no sign that the sick workers can spread the illness to others, Gerberding told The Associated Press.
Nor is there any sign that this is a foodborne illness, said Dr. James Sejvar, a CDC neurologist dispatched to Indiana to study the cases firsthand.
CDC is calling the condition progressive inflammatory neuropathy - meaning something is triggering inflammation serious enough to damage nerves.
Since December, 12 meatpackers in Austin, Minn., and two at a plant in Indiana have reported symptoms ranging from numbness, tingling and worsening weakness in their arms and legs to paralysis. A few are severely disabled; others have returned to work.
All 14 employees worked near powerful compressed air systems that blow brains out of pig heads at what is known as the head table. Both plants have stopped using the process.
Investigators have ruled out many of the prime suspects, including a number of toxins, known viruses and industrial chemicals. Now a chief theory is that contact with pig brain tissue is somehow triggering an autoimmune reaction, where the body's immune system goes out of control and attacks its own tissue, Sejvar said.
They haven't completely ruled out the possibility of an infectious agent, he said.
