Jun 14, 2011 (CIDRAP News) A Campylobacter jejuni outbreak that sickened close to 100 people in Alaska in 2008 had a surprising cause: fresh peas contaminated by sandhill cranes, according to a report in Clinical Infectious Diseases.
"This is the first reported outbreak of campylobacteriosis linked to produce contaminated with bird feces," says the report by researchers from the Centers for Disease Control and Prevention and several Alaska state agencies.
C jejuni is one of the most common bacterial causes of diarrheal illness, with an estimated 2.4 million cases annually, but few cases are part of recognized outbreaks, the report says. Though the illness is usually linked to contaminated food or water, it's hard to trace the organism to a particular vehicle, because it doesn't survive long outside an animal host.
But in the Alaska outbreak, investigators managed to confirm the pathogen in pea samples and sandhill crane feces and to match those isolates to some of the isolates from sick patients, according to the report.
The outbreak began in late August of 2008 with the reporting of 10 lab-confirmed campylobacteriosis cases in Anchorage residents. Three of the 10 isolates were matched by pulsed-field gel electrophoresis (PFGE). The cases triggered an alert to the public and a multi-pronged investigation.
A case-control study involving 45 patients with confirmed campylobacteriosis and 90 healthy controls pointed to consumption of raw peas as the only significant risk factor. Overall, 98 people had illnesses that met the case definition, and 63 cases were lab-confirmed, the report says.
Patients had diarrhea for a median of 9 days, and 5 patients were hospitalized. No one died, but one patient experienced Guillain-Barre syndrome, a paralytic condition sometimes associated with Campylobacter infection. The patent was in intensive care for 31 days and subsequently needed neurologic rehabilitation.
Investigators traced the peas eaten by patients to the only farm in Alaska known to produce shelled peas for sale, the report says. The farm is located about 10 miles from the Palmer Hay Flats, a wildlife refuge where about 20,000 sandhill congregate in summer. The farm owner told food safety inspectors that cranes visited pea fields daily during harvest time.
The inspectors found various food safety gaps at the farm, including a lack of chlorine in pea-processing water, inadequate plumbing in the processing area, and inadequate work surfaces for processing. The farmer took corrective actions and agreed to undergo annual safety audits, and no increases in Campylobacter cases occurred during the 2009 and 2010 seasons, the report says.
Of 36 environmental samples collected by investigators, 16 tested positive for C jejuni14 crane-feces samples and 2 pea samples. The authors say they identified 25 unique PFGE patterns in isolates from patients, and four of these patterns, found in 15 patients, matched patterns seen in the two pea samples and in three crane-feces samples.
The report notes that single environmental samples yielded up to seven different C jejuni strains, and consequently individual patients were probably infected with more than one strain.
The report concludes that the outbreak "underscores the need to consider wild-bird feces as an underrecognized source of produce contamination worldwide. Identification of this novel food vehicle further emphasizes the need to better understand the ecologies and reservoirs of Campylobacter and other foodborne zoonotic pathogens, and to develop additional control measures to prevent or reduce contamination of fresh produce."
Gardner TJ, Fitzgerald C, Xavier C, et al. Outbreak of campylobacteriosis associated with consumption of raw peas. J Infect Dis 2011 Jul 1;53(1):26-32 [Abstract]