I suppose it’s never reassuring to hear about a Mystery Disease Among Slaughterhouse Workers, even if it doesn’t sound contagious:
Three patients had the same highly unusual set of symptoms: fatigue, pain, weakness, numbness and tingling in the legs and feet.
The patients had something else in common, too: all worked at Quality Pork Processors, a local meatpacking plant.
The disorder seemed to involve nerve damage, but doctors had no idea what was causing it.
Tests showed that the man’s spinal cord was markedly inflamed. The cause seemed to be an autoimmune reaction: his immune system was mistakenly attacking his own nerves as if they were a foreign body or a germ. Doctors could not figure out why it had happened, but the standard treatment for inflammation — a steroid drug — seemed to help. (The patient was not available for interviews.)
Neurological illnesses sometimes defy understanding, Dr. Lachance said, and this seemed to be one of them. At the time, it did not occur to anyone that the problem might be related to the patient’s occupation.
By spring, he went back to his job. But within weeks, he became ill again. Once more, he recovered after a few months and returned to work — only to get sick all over again.
By then, November 2007, other cases had begun to turn up. Ultimately, there were 12 — 6 men and 6 women, ranging in age from 21 to 51. Doctors and the plant owner, realizing they had an outbreak on their hands, had already called in the Minnesota Department of Health, which, in turn, sought help from the federal Centers for Disease Control and Prevention.
Though the outbreak seemed small, the investigation took on urgency because the disease was serious, and health officials worried that it might indicate a new risk to other workers in meatpacking.
“It is important to characterize this because it appears to be a new syndrome, and we don’t truly know how many people may be affected throughout the U.S. or even the world,” said Dr. Jennifer McQuiston, a veterinarian from the disease centers.
In early November, Dr. Aaron DeVries, a health department epidemiologist, visited the plant and combed through medical records. The disease bore no resemblance to mad cow disease or to trichinosis, the notorious parasite infection that comes from eating raw or undercooked pork. Nor did it spread person to person — the workers’ relatives were unaffected — or pose any threat to people who ate pork.
A survey of the workers confirmed what the plant’s nurses had suspected: those who got sick were employed at or near the “head table,” where workers cut the meat off severed hog heads.
On Nov. 28, Dr. DeVries’s boss, Dr. Ruth Lynfield, the state epidemiologist, toured the plant. She and the owner, Kelly Wadding, paid special attention to the head table. Dr. Lynfield became transfixed by one procedure in particular, called “blowing brains.”
As each head reached the end of the table, a worker would insert a metal hose into the foramen magnum, the opening that the spinal cord passes through. High-pressure blasts of compressed air then turned the brain into a slurry that squirted out through the same hole in the skull, often spraying brain tissue around and splattering the hose operator in the process.
The brains were pooled, poured into 10-pound containers and shipped to be sold as food — mostly in China and Korea, where cooks stir-fry them, but also in some parts of the American South, where people like them scrambled up with eggs.
The person blowing brains was separated from the other workers by a plexiglass shield that had enough space under it to allow the heads to ride through on a conveyor belt. There was also enough space for brain tissue to splatter nearby employees.
“You could see aerosolization of brain tissue,” Dr. Lynfield said.
The workers wore hard hats, gloves, lab coats and safety glasses, but many had bare arms, and none had masks or face shields to prevent swallowing or inhaling the mist of brain tissue.
Dr. Lynfield asked Mr. Wadding, “Kelly, what do you think is going on?”
The plant owner watched for a while and said, “Let’s stop harvesting brains.”
Quality Pork halted the procedure that day and ordered face shields for workers at the head table.
Epidemiologists contacted 25 swine slaughterhouses in the United States, and found that only two others used compressed air to extract brains. One, a plant in Nebraska owned by Hormel, has reported no cases. But the other, Indiana Packers in Delphi, Ind., has several possible cases that are being investigated. Both of the other plants, like Quality Pork, have stopped using compressed air.
But why should exposure to hog brains cause illness? And why now, when the compressed air system had been in use in Minnesota since 1998?
At first, health officials thought perhaps the pigs had some new infection that was being transmitted to people by the brain tissue. Sometimes, infections can ignite an immune response in humans that flares out of control, like the condition in the workers. But so far, scores of tests for viruses, bacteria and parasites have found no signs of infection.
As a result, Dr. Lynfield said the investigators had begun leaning toward a seemingly bizarre theory: that exposure to the hog brain itself might have touched off an intense reaction by the immune system, something akin to a giant, out-of-control allergic reaction. Some people might be more susceptible than others, perhaps because of their genetic makeup or their past exposures to animal tissue. The aerosolized brain matter might have been inhaled or swallowed, or might have entered through the eyes, the mucous membranes of the nose or mouth, or breaks in the skin.