Investigation of Progressive Inflammatory Neuropathy Among Swine

depar depar depar depar department of health and human ser tment of health and human ser tment of health and human ser tment of health and human ser tment of health and human services vices vices vices vices the Minnesota Department of Health (MDH) was notified by a tertiary-care provider of unexplained neurologic illnesses among workers in a swine slaughterhouse (plant A) in southeast Minnesota. As a result , MDH initiated a detailed investigation at plant A to characterize the outbreak. This report describes the ongoing investigation and outbreak-control measures undertaken by state public health officials and CDC. Plant A, located in southeastern Minnesota, employs approximately 1,200 workers and processes 18,000 pigs per day. After being notified of the illnesses, MDH investigators initiated active case finding, interviewed workers at plant A, and reviewed the plant's occupational health and employment records. As of January 28, 2008, a total of 12 workers at plant A had been identified with confirmed (eight workers), probable (two), or possible (two) progressive in-flammatory neuropathy (PIN) (Box). Illness onset ranged from November 2006 through November 2007. Median age of the 12 patients was 31 years (range: 21–51 years); six patients were female. All 12 patients reported being healthy before the onset of neurologic symptoms. 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 ax-onal or demyelinating peripheral neuropathy by electrodiagnostic testing. Cerebrospinal fluid was obtained from seven patients. All seven had elevated protein levels (median: 125 mg/dL; range: 75–231 mg/dL [normal: 14– 45 mg/dL]) with no or minimal pleocytosis (median: 1 cell/dL; range: 1–73 cells/dL in a nontraumatic tap); five patients had evidence of inflammation on spinal magnetic resonance imaging (four patients in peripheral nerves or roots and one patient in the anterior spinal cord). All 12 patients reported either working at or having regular contact with an area where swine heads were processed (known as the head table), which was located within a larger processing area in plant A known as the warm room. A case-control study was conducted among plant A workers to identify specific risk factors associated with illness. The 10 patients with confirmed or probable cases were included BOX. Working case definition for progressive inflammatory neuropathy among swine slaughterhouse workers, 2007–2008 Epidemiologic criterion …