Preliminary Incidence and Trends of Infections With Pathogens Transmitted Commonly Through Food

Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2015-2018

Danielle M. Tack, DVM; Ellyn P. Marder, MPH; Patricia M. Griffin, MD; Paul R. Cieslak, MD; John Dunn, DVM; Sharon Hurd, MPH; Elaine Scallan, PhD; Sarah Lathrop, PhD; Alison Muse, MPH; Patricia Ryan, MD; Kirk Smith, DVM; Melissa Tobin-D'Angelo, MD; Duc J. Vugia, MD; Kristin G. Holt, DVM; Beverly J. Wolpert, PhD; Robert Tauxe, MD; Aimee L. Geissler, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2019;68(16):369-373. 

In This Article

Discussion

Campylobacter has been the most commonly identified infection in FoodNet since 2013. It causes diarrhea, sometimes bloody, and 18% of persons are hospitalized. A rare outcome of Campylobacter infection is Guillain-Barré syndrome, a type of autoimmune-mediated paralysis. Poultry is a major source of Campylobacter.[2] In August 2018, FSIS began using a new testing method; in a study of that method, Campylobacter was isolated from 18% of chicken carcasses and 16% of chicken parts sampled.[3] FSIS currently makes aggregated test results available and intends to update performance standards for Campylobacter contamination.

The incidence of infections with Enteritidis, the most common Salmonella serotype, has not declined in over 10 years. Enteritidis is adapted to live in poultry, and eggs are an important source of infection.[4] By 2012, FDA had implemented the Egg Safety Rule, which requires preventive measures during the production of eggs in poultry houses and requires subsequent refrigeration during storage and transportation, for all farms with ≥3,000 hens. In 2018, a multistate outbreak of Enteritidis infections was traced to eggs from a farm that had not implemented the required egg safety measures after its size reached ≥3,000 hens.[5] Chicken meat is also an important source of Enteritidis infections.[4] In December 2018, FSIS reported that 22% of establishments that produce chicken parts failed to meet the Salmonella performance standard (USDA-FSIS Salmonella verification testing program**). The percentage of samples of chicken meat and intestinal contents that yielded Enteritidis were similar in 2018 to those during 2015–2017 (USDA-FSIS, unpublished data). In contrast, a decline in serotype Typhimurium isolated from the same sources was observed during the same period. This trend coincides with declines in Typhimurium human illnesses. Changes in poultry production practices, including vaccination against Typhimurium, might have resulted in these declines.[6] In the United Kingdom, vaccination of both broiler and layer chickens against Enteritidis, along with improved hygiene, was followed by a marked decrease in human Enteritidis infections.[7]

Produce is a major source of foodborne illnesses.[2] During 2018, romaine lettuce was linked to two multistate outbreaks of STEC O157 infections.[8] The marked increase in reported Cyclospora infections was likely attributable to several factors including produce outbreaks and continued adoption of DNA-based syndrome panel tests.[1] Improved agricultural practices are needed to prevent produce-associated infections. FDA provides technical assistance to task forces created by the produce industry, to determine how to prevent contamination of romaine lettuce and facilitate outbreak investigations by improving product labeling and traceability. In 2018, FDA expanded surveillance sampling of foreign and domestically grown produce to assess its safety.[9] FDA is implementing the Produce Safety Rule,†† with routine inspections of large produce farms planned this spring. Because produce is a major component of a healthy diet and is often consumed raw, making it safer is important for improving human health.[10]

The findings in this report are subject to at least three limitations. First, the changing diagnostic landscape makes interpretation of incidence and trends more complex. Increases in reported incidence might be attributable entirely, or in part, to changes in clinician ordering practices, increased use of DNA-based syndrome panels that identify pathogens not routinely captured by traditional methods, and changes in laboratory practices in response to the availability of these panels. Second, some CIDT results might be false positives. Finally, year-to-year variations, attributable in part to large outbreaks, might not indicate sustained trends.

The need to obtain and subtype isolates from ill persons is becoming an increasing burden to state health departments but is critical for maintaining surveillance to detect and investigate outbreaks, evaluating prevention efforts, and developing targeted control measures. Measures that might decrease foodborne illnesses include enhanced efforts targeting Campylobacter contamination of chicken; strengthening prevention measures during egg production, especially within small flocks; vaccinating poultry against Salmonella serotype Enteritidis; decreasing Salmonella contamination of produce, poultry, and meat; and continued implementation of the Food Safety Modernization Act, specifically FDA's Produce Safety Rule. FoodNet continues to collect data and develop analytic tools to adjust for changes in diagnostic testing practices and test characteristics. These actions, along with FoodNet's robust surveillance, provide data to help evaluate the effectiveness of prevention efforts and determine when additional measures are needed.

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