Date: Thu 17 Jan 2008
In the fall of 2007, clinicians at the Mayo Clinic in Rochester, Minnesota, notified the Minnesota Department of Health of an unusual cluster of 12 patients with inflammatory neuropathy occurring between November 2006 and November 2007 among workers at a pork processing plant in Minnesota. An initial investigation has revealed that they all have worked in the same area of the plant where the heads of the pig are processed. The investigation in Minnesota is ongoing and additional patients have been identified in Indiana, among workers in a similar plant. At this point an etiologic agent has not been identified.
These patients have frequently had illness onset with pain, numbness, and tingling in the extremities. The illness typically progressed with development of relatively symmetric mild to moderate weakness involving predominantly the distal lower limbs. Occasionally, facial weakness has also been observed. They often complain of difficulty with balance (ataxia). Electro diagnostic testing showed prolonged motor distal latencies and F-wave latencies, minimal sensory nerve conduction abnormality, and evidence of mild denervation of distal muscles on EMG (electromyography).
Of the cases in which cerebrospinal fluid (CSF) has been obtained, all have had elevated CSF protein, with minimal if any pleocytosis (such as, cytoalbuminologic dissociation). Thoracic and lumbar magnetic resonance imaging has demonstrated mildly thickened nerve roots and contrast enhancement. Time of illness progression ranged from several days to months with severity of illness ranging from mild weakness in most cases to paraplegia in one. Most have had some level of recovery.
Given the apparent close association of these patients with participation in the processing of pig head material, it is possible that similar illnesses are occurring at other pork processing plants. The CDC is requesting neurologists to provide information about patients who may have developed illnesses similar to that reported by the Mayo Clinic. In particular, neurologists who have diagnosed patients with peripheral neuropathy, myelopathy, or a mixed clinical presentation of peripheral/central (and, more specifically, myelopathic) involvement in persons with exposure to pig butchering or processing during the past year are asked to report this information to their state health department, and contact the CDC at 770-488-7100.
