Workers at swine slaughterhouses develop neurologic illnesses

The national Centers for Disease Control and Prevention and the Minnesota Department of Health are investigating an outbreak of neurologic illnesses among workers at a Minnesota swine slaughterhouse.

The plant employs about 1,200 workers and processes about 18,000 pigs per day. The MDH learned of the illnesses on Oct. 29, 2007, and initiated an investigation. As of Jan. 28, investigators identified eight workers with progressive inflammatory neuropathy and four workers with probable or possible PIN.

The onset of illness was from November 2006 through November 2007. Symptoms ranged from acute paralysis to gradually progressive symmetric weakness.

All 12 patients reported having regular contact with an area for processing pig heads. The plant used a compressed-air device to harvest brain tissue. In response to the investigation, the plant voluntarily suspended harvesting of brains and instituted additional mandatory personal protective equipment for workers in the head-processing area.

A survey of large swine slaughterhouses found only two other plants that reported recent use of compressed air for extracting pig brains. Investigators did not identify any cases of PIN in association with workers at a plant in Nebraska. Investigators identified several workers at an Indiana plant with neurologic illnesses and similar histories of exposure to head-processing activities. As a result of the investigation, both plants have stopped using compressed air to extract brain material.

One hypothesis for development of PIN is that worker exposure to aerosolized pig neural protein might have induced an autoimmune-mediated peripheral neuropathy.