Progressive Inflammatory Neuropathy Ails Slaughterhouse Workers
A continuing investigation of progressive inflammatory neuropathy (PIN) in swine slaughterhouse workers in the CDC’s MMWR details illnesses among workers in a slaughterhouse in southeastern Minnesota (referred to only as Plant A). Six workers have confirmed, two have probable, and two have possible PIN.
According to the MMWR,
Symptoms ranged from acute paralysis to gradually progressive symmetric weakness over periods ranging from 8 to 213 days. Severity ranged from minor weakness and numbness to paralysis predominantly in the lower extremities affecting mobility. Eleven patients had evidence of axonal or demyelinating peripheral neuropathy by elctrodiagnostic testing.
Results of the case-control study indicated that case patients (seven of 10, 70%) were significantly more likely to have worked at the head table than the warm-room controls (12 of 48, 25%) (odds ratio [OR]: 7.0; 95% confidence interval [CI] = 1.3–42.2; p = 0.009). Case-patients also were more likely to have removed brains or remaining skeletal muscle from the pig head (a process known as backing heads) (four of 10, 40%) than controls (two of 46, 4%) (OR: 15.3; CI = 1.8–163.4; p = 0.006). Among head table workers, case-patients were significantly more likely to have removed brains or skeletal muscle from the head (four of seven, 57%) than head-table controls (eight of 65, 12%) (OR: 9.50; CI = 1.40–70.2; p = 0.01). Illness was not determined to be associated with previous travel outside or within the United States; exposure to chemicals, fertilizers, or insecticides; use of medications; or receipt of previous vaccinations.
Environmental assessments of the plant noted that a compressed air device was used to harvest brain tissue from the pig heads (known as “blowing brains”). This device caused brain splatter and may also have aerosolized brain matter which the workers may have breathed. Since the assessment, Plant A has increased worker protection by including face masks and has suspended the harvesting of brains.
Only three other plants (one in Nebraska, one in Indiana) investigated reported using compressed air machines to harvest brains. No cases of PIN were reported in Nebraska; however, several illnesses have been reported in Indiana under similar circumstances to Plant A. It is important to note that the investigation only shows workers at the head table who used compressed air machines may be at risk, possibly because exposure to aerosolized pig neural protein may have induced an autoimmune-mediated peripheral neuropathy. All material processed at the plant passed inspection by FSIS and allegedly has not presented any risk of foodborne illness to the general population.
