Inflammatory Peripheral Neuropathies Prevalent in Poultry and Swine Farmers

Crina Frincu-Mallos, PhD

November 18, 2009

November 18, 2009 (Philadelphia, Pennsylvania) — Symptoms associated with inflammatory peripheral neuropathies are significantly higher in farm workers exposed to poultry and swine, researchers reported here at the American Public Health Association 137th Annual Meeting.

Food-borne infection with Campylobacter jejuni, a common pathogen associated with poultry and swine exposure, is considered a major risk factor for peripheral neuropathies, including Guillain-Barré syndrome, said Meghan F. Davis, DVM, MPH, a PhD student from the Department of Environmental Health Sciences at Johns Hopkins School of Public Health in Baltimore, Maryland.

Campylobacteriosis, the disease produced by bacteria of the genus Campylobacter, affects more than 2.4 million people each year, close to 1% of the population of the United States. Guillain-Barré syndrome is the leading cause of acute peripheral neuropathy worldwide. According to the Centers for Disease Control and Prevention, 3000 to 6000 people in the United States develop Guillain-Barré syndrome each year.

"These are diseases [that farm workers] may develop as a result of their contact with farm birds and animals and the pathogens they carry," Dr. Davis said in an interview with Medscape Public Health & Prevention. The bacteria are usually found in poultry but have also been isolated in swine, putting farm workers at increased risk of becoming carriers and potentially developing neurologic disease.

Among swine farmers and workers, the risk for numbness was 18% and 23% higher, respectively, than among control subjects. The risk for weakness was 22% and 28% higher, respectively, than among control subjects (P < .05).

Among poultry farmers and workers, the risk for numbness was significantly higher than among control subjects (27% vs 25%; P < .05). No increase in self-reported speech or vision problems was observed, note the investigators.

"Our findings strongly suggest that [farmers and farm workers] are going to be at higher risk," she cautioned.

"The public health significance is that we need to focus on farm worker safety, potentially using more protective gear and educational programs, and doing more surveillance for diseases that they might develop as a result of their contact with farm animals and birds," said Dr. Davis.

A total of 52,395 farmers from North Carolina and Iowa were recruited from the Agricultural Health Study between 1993 and 1997. A complete set of data for key symptoms and exposures was available for 20,599 participants. Of these, 15,932 farmers and workers were exposed to swine and poultry.

Swine farmers (n = 7079), swine confinement workers (n = 5930), poultry farmers (n = 784), and poultry workers (n = 713) were evaluated for possible exposure to C jejuni and compared with farmers who reported no occupational animal exposure.

Symptoms relevant to inflammatory peripheral neuropathies, such as numbness, weakness, blurred vision, and night blindness, were examined for the purpose of this retrospective analysis.

Exposure to birds and pigs was used as a surrogate for Campylobacter exposure, explained the investigators, who sought to determine whether exposure increased the prevalence of neurologic symptoms in this cohort.

"What we are going to do as a follow-up is to look more closely at this association, using biomarkers to assess whether the association is very specific to C jejuni and Guillain-Barré syndrome," Dr. Davis said. They are planning a prospective study of "either established farm workers (or processing plant workers) or [workers] new to these work occupations, and [intend to] follow them over time to see if they have a higher risk for the development of this particular disease."

"A very well-run study," said Lee Hurt, MPH, an epidemiologist with the Center for Maternal and Child Health, Maryland Department of Health and Mental Hygiene in Baltimore. Dr. Hurt expressed her interest in "the effects of farm work on public health" in an interview with Medscape Public Health & Prevention.

Controlling pathogens like C jejuni at the farm level might help reduce risks for occupational exposure and address concerns regarding food-borne disease, conclude the investigators.

The work was supported in part by grants from the National Institute of Environmental Health Sciences. Dr. Davis and Ms. Hurt have disclosed no relevant financial relationships.

American Public Health Association (APHA) 137th Annual Meeting: Abstract 213221. Presented November 8, 2009.

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