CDC cites increases in Campylobacter, Vibrio infections

Apr 18, 2013 (CIDRAP News) – The overall US incidence of major foodborne diseases was about the same in 2012 as it was about 5 years earlier, but Campylobacter infections were significantly more common, for unclear reasons, federal officials announced today.

The annual foodborne disease report from the Centers for Disease Control and Prevention (CDC) showed that Campylobacter incidence was 14% higher in 2012 than in the CDC's chosen baseline period of 2006-08 and was at the highest level since 2000. Oddly, the findings come as federal officials report seeing signs of reduced Campylobacter contamination in poultry, regarded as the most common source of the pathogen.

The other exception to the generally static foodborne disease picture was the incidence of Vibrio infections, which was 43% higher than in the baseline period, though the shellfish-linked illnesses remain rare.

The data come from the CDC's FoodNet foodborne disease surveillance system, which tracks culture-confirmed cases of major foodborne diseases in 10 states with about 15% of the US population.

At a press conference today, Robert Tauxe, MD, MPH, deputy director of the CDC's Division of Foodborne, Waterborne, and Environmental Diseases, said the overall incidence of six key foodborne pathogens "is down 22% from where we were in the late 1990s, although in the last few years, since 2006 to 2008, it really hasn't changed."

The CDC presented the full FoodNet findings in today's issue of Morbidity and Mortality Weekly Report. The article says 19,531 infections, 4,563 hospitalizations, and 68 deaths associated with foodborne diseases were reported in 2012. For most of the pathogens, incidence was highest in children under age 5, while hospitalizations and deaths were most common in those over 65.

Salmonella infections were most common, with a rate of 16.42 cases per 100,000 population. That was down a bit from 16.47 in 2011 but well above the federal "Healthy People 2020" objective of 8.5.

Campylobacter was second most common, at 14.30 cases per 100,000, nearly the same as last year's 14.31, though well above the 2006-08 baseline. The 2020 goal for Campylobacter is 8.5 per 100,000.

Incidences (per 100,000) for the other major pathogens are as follows, with the 2011 figures and the 2020 objectives shown for comparison:

  • Shigella, 4.5 (3.21, no 2020 goal set)
  • Cryptosporidium, 2.60 (2.83, no goal set)
  • Shiga toxin–producing Escherichia coli (STEC) O157, 1.12 (0.98, 0.6)
  • STEC non-O157, 1.16 (1.08, no goal set)
  • Vibrio, 0.41 (0.33, 0.2)
  • Yersinia, 0.33 (0.34, 0.3)
  • Listeria, 0.25 (0.28, 0.2)
  • Cyclospora, 0.03 (0.05, no goal set)

The increase in STEC O157 cases in 2012 marked a turnaround from a downward trend since 2006, and it now exceeds the previous federal goal for 2010 of 1 case per 100,000, the report says. Meanwhile, the continued increase in non-O157 E coli cases probably reflects the increased use of tests that detect those infections.

Because of changing lab technology, the real numbers for Campylobacter and E coli O157 and non-O157 may be higher than what FoodNet found, the CDC said. FoodNet relies on detecting bacterial pathogens by growing them from clinical specimens, but labs are expanding their use of "culture-independent" tests for Campylobcter and E coli.

Data from patients with only culture-independent test results suggest that in 2012, the count of lab-identified Campylobacter cases could have been 9% higher and the number of STEC (O157 and non-O157) cases might have been 7% to 19% higher than in the FoodNet findings, the CDC report says.

Officials at the press conference acknowledged being puzzled by the upward trend in Campylobacter infections.

David Goldman, MD, MPH., assistant administrator of the Office of Public Health Science in the US Department of Agriculture's (USDA's) Food Safety and Inspection Service (FSIS), noted that in 2011 the FSIS set its first performance standard to limit Campylobacter contamination in chicken and turkey.

Compared with findings from a 2007-08 baseline study, he said, "The evidence we have . . . is that Campylobacter contamination is decreasing, at least on whole chickens and whole turkeys."

In response to questions about the seeming contradiction between the Campylobacter incidence and contamination findings, Jeff Farrar, DVM, PhD, of the US Food and Drug Administration (FDA), said, "These are questions we're asking ourselves right now." He is the FDA's director of intergovernmental affairs and partnerships.

He said campylobcteriosis often occurs as a sporadic illness rather than as part of an identified outbreak, adding, "We don't always have a clear link to a causative agent or vehicle or food." A working group of FDA, CDC, and USDA officials is currently trying to determine what percentage of Campylobacter cases are due to poultry versus other foods, he said.

Tauxe commented that Campylobacter has also been associated with raw milk and raw produce. "The easy assumption that it's mostly poultry has been the default assumption, but it's not one we should accept without question," he said. "There are methods we're exploring to do that attribution better."

In other comments, Farrar said the report points up the importance of new rules to be implemented under the FDA Food Safety Modernization Act and predicted that the changes will help reduce foodborne illnesses. The agency has proposed regulations on general preventive controls for food processors and rules for improving produce safety.

The Consumer Federation of America said today that the CDC report shows that food safety progress remains "stalled." The group had some criticism for the USDA.

"Salmonella and Campylobacter illnesses are frequently associated with raw or undercooked poultry," the federation said in a statement. "Much of the poultry that consumers purchase in the supermarket is sold as parts, yet the Food Safety and Inspection Service has only collected data on whole birds, not on the level of contamination of poultry parts. The agency is in the midst of a study of poultry parts, but has not yet published any data. Additionally, whole birds purchased at retail and tested by consumer groups have shown unacceptably high rates of Salmonella and Campylobacter.

"The lack of progress in reducing illnesses from these pathogens is particularly concerning as the Food Safety and Inspection Service is seeking to implement a new inspection program for poultry, yet the agency has almost no data on how the proposed program will actually affect Campylobacter rates on poultry," the group added. "The agency's proposal also does not require poultry plants to test for Salmonella and Campylobacter, significantly limiting the agency's ability to assure that poultry plants are reducing contamination from these pathogens."

CDC. Incidence and trends of infection with pathogens transmitted commonly through food—Foodborne Diseases Active Surveillance Network, 10 U.S. sites, 1996-2012. MMWR 2013 Apr 19;62(15) [Full text]

See also:

Apr 18 CDC news release on the report

Apr 18 Consumer Federation press release

Jul 30, 2012, CIDRAP News story on last year's FoodNet report

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