Neurologic Symptoms Associated With Raising Poultry and Swine Among Participants in the Agricultural Health Study

Workers in agriculture face a variety of occupational risks, including exposures to pathogens. These exposures can be associated not only with acute infection but also with long-term sequelae, such as neurologic disease. Guillain-Barre Syndrome (GBS), an autoimmune disorder, is the major cause of acute peripheral neuropathy in the world.1 Clinically, patients affected by GBS or GBS-like illness present with symptoms that range from weakness and tingling in affected limbs to a life-threatening, ascending paralysis.1,2 Worldwide, incidence of GBS ranges from 0.6 to 4 cases per 100,000 population.3 Men are 1.5 times more likely to develop the autoimmune neuropathy than women.3 GBS in the United States may carry an economic burden of up to $420 million.4 The major identified risk factor for GBS is infection by the bacterial pathogen Campylobacter jejuni.1,5,6 In a literature review, C. jejuni infection preceded 30% to 40% of cases of GBS.1 Other studies have demonstrated increased risk of GBS in the two months after an episode of C. jejuni infection.6,7 Clusters of GBS cases may occur after outbreaks of bacterial enteritis.3 Other risk factors for GBS include other prior infections, for example, with cytomegalovirus, Epstein-Barr virus, influenza, or Mycoplasma pneumoniae.3,5 The putative mechanism underlying this association is autoimmunity induced by a cross-reacting mimicry between surface antigens of C. jejuni and corresponding epitopes of the host peripheral nervous system.8,9 Antibodies to variant C. jejuni lipooligosaccharides cross-react with human neuronal gangliosides to cause the pathophysiological events that induce autoimmune peripheral neuropathy.10 Particular subtypes of C. jejuni, such as HS:19 and HS:041, are more closely linked to the development of GBS, which is associated with polymorphisms in specific genes that encode variant surface proteins.11–13 Variation in host immunity also plays a role in determining individual susceptibility for developing GBS after infection.8,9 Studies describing associations between GBS and C. jejuni infection primarily have examined infections associated with poultry consumption.14,15 The occupational risks for C. jejuni exposure among workers in food animal production have been well-described16,17 Because Campylobacter is carried commensally by poultry and often is isolated from swine, occupational contact with these animals is associated with increased risks of C. jejuni carriage, particularly under conditions of concentrated animal-feeding operations.18 In 2007, Price et al.19 reported on increased risks of neurologic symptoms indicative of Guillain-Barre--like peripheral neuropathy in a relatively small cross-sectional study of poultry workers. The present study builds on these results by examining prevalence of symptoms consistent with peripheral neuropathy in a large cohort of farmers: the Agricultural Health Study (AHS). Our motivation for using available data from the AHS came, in large part, from our interest in identifying a viable population for a future cohort study of inflammatory peripheral neuropathy.