Report ranks food-pathogen pairs by disease impact

Apr 28, 2011 (CIDRAP News) – Most of the foodborne illnesses in the United States are caused by a fairly short list of pathogens in a limited number of foods, with Salmonella, Campylobacter, and poultry ranking high, the University of Florida's Emerging Pathogens Institute said in a lengthy report released today.

The report cites Salmonella as the leading foodborne pathogen, while Campylobacter-tainted poultry leads a list of the 10 food-and-pathogen combinations causing the biggest burdens on public health. Also, poultry leads a list of the 12 food categories associated with the most disease.

Second on the top 10 list of food-pathogen pairs is pork contaminated with a relatively low-profile pathogen, Toxoplasma gondii. Toxoplasma, a single-cell parasite that millions of American may carry, also ranks second on the list of pathogens. But the report cautions that data on Toxoplasma in food are scarce.

The researchers say their report, Ranking the Risks: The 10 Pathogen-Food Combinations with the Greatest Burden on Public Health, is the first comprehensive ranking of such combinations that has been done for the United States.

The aim of the report is to improve food safety efforts, especially by government. "Government agencies must work together to effectively target their efforts," said lead author Michael Batz in a press release. "If we don't identify which pairs of food and microbes present the greatest burden, we'll waste time and resources and put even more people at risk."

Estimation approach
The authors estimated the disease burden for pathogens and foods in terms of dollar costs and quality-adjusted life-years (QALYs) lost. They developed a tool called the Foodborne Illness Risk Ranking Model and used it to analyze data from more than 10 years of foodborne illness outbreaks. They also conducted a peer-reviewed survey of close to 50 experts, the report says.

The researchers focused on 14 pathogens and 12 different types of foods, estimating the impact of 168 food-pathogen pairs.

Overall, the report estimates that the 14 pathogens cost the nation $14.1 billon a year and cause 8.9 million illnesses, 53,678 hsopitalizations, 61,461 QALYs lost, and 1,322 deaths. But more than 90% of the burden can be traced to five pathogens, in order: Salmonella, Toxoplasma, Campylobacter, Listeria monocytogenes, and norovirus.

(The reports lists Campylobacter and Listeria as tied for third place in impact, followed by norovirus in fifth place, with Clostridium perfringens and E coli O157:H7 tied for sixth.)

Top 10 combinations
Looking at the top 10 food-pathogen combinations, the authors say Campylobacter-tainted poultry leads the list, causing more than 600,000 illnesses and 55 deaths a year, as well as $1.3 billion in economic impact and 9,500 QALYs lost.

The other nine pathogen-food combinations and their impacts, in descending order, are:

  • Toxoplasma in pork: $1.2 billion and 4,500 QALYs
  • Listeria in deli meats: $1.2 billion and 4,000 QALYs
  • Salmonella in poultry: $700 million and 3,600 QALYs
  • Listeria in dairy products: $700 million and 2,600 QALYs
  • Salmonella in complex foods: $600 million and 3,200 QALYs
  • Norovirus in complex foods: $900 million and 2,300 QALYs
  • Salmonella in produce: $500 million and 2,800 QALYs
  • Toxoplasma in beef: $700 million and 2,500 QALYs
  • Salmonella in eggs: $400 million and 1,900 QALYs

Taken together, the top 10 food-pathogen pairs cause $8.1 billion in medical costs and lost wages, according to the report. They lead to about 3.9 million illnesses, 39,915 QALYs lost, and 765 deaths.

Considering food categories, the report says poultry causes more foodborne disease than any other kind o food. "Contaminated poultry is responsible for $2.4 billion in costs of illness, primarily due to Salmonella and Campylobacter," it states.

The authors say the US Department of Agriculture (USDA) should consider toughening its recently announced performance standards for these two pathogens in chicken and turkey, which take effect in July. "The new standards are expected to reduce illness from these pathogens by just 1 to 2%, not enough to make a big difference from a public health standpoint."

The National Chicken Council, an industry group, commented on the report today, saying the levels of pathogenic microbes on raw chicken have been greatly reduced in recent years. "According to USDA sampling, the microbiological profile of fresh chicken meat is the best that it has ever been," the council said.

It asserted that most processing plants are already meeting both the USDA's new Salmonella and Campylobacter standards, adding, "The Florida project acknowledges a lack of outbreak data on Campylobacter and may not have captured improvements made by the industry in processing raw chickens."

Toxoplasma complexities
While citing Toxoplasma as an important foodborne pathogen, the Florida researchers say much better information about it is needed.

The parasite "is not a 'front-page' pathogen, but it is very important from a public health standpoint," the report states. The Centers for Disease Control and Prevention (CDC) estimates that foodborne toxoplasmosis causes 327 deaths annually, second only to Salmonella. Although Toxoplasma is usually associated with handling of cats and kitty litter, the CDC now estimates that half of toxoplasmosis cases are foodborne. More than 60 million Americans may carry T gondii, according to information on the CDC Web site.

But there is little good information about which foods have Toxoplasma contamination, the Florida report says. It "has historically been associated with pork, but tests on pork show a major decline over the last 15 years, while a recent case-control study by CDC found the leading foodborne risks to be eating raw ground beef, rare lamb, or locally produced cured, dried, or smoked meat," it explains.

In other observations, the report says that four of the top 10 pathogen-food combinations pose major risks during pregnancy. Listeria and Toxoplasma, in particular, can lead to miscarriage, stillbirth, or life-long problems in the affected child.

The document also notes that improper practices in restaurants and other retail outlets may cause a "substantial amount" of foodborne disease. Threfore, state and local efforts are a critical part of the food safety system and should be strengthened.

Finally, the authors caution, "Our results are limited by uncertainties in underlying data, none more so than gaps in our ability to confidently attribute cases of foodborne illnesses to specific foods."

And the press release advises that "people should use this report not as a top 10 list of foods to avoid, but as a reminder that many of the foods we eat every day can become contaminated."

Consumer group welcomes report
Chris Waldrop, a spokesman for the Consumer Federation of America, based in Washington, DC, praised the report today, saying it is important on several counts.

"One is, if you look at the pathogen-food pairs, you see a lot of meat and pultry in there," he said. "I think that's a continued reminder that meant and poultry continues to be a problem and continues to cause foodborne illness, and we need to figure out ways to address this."

He commented that much time and effort went into enacting the new FDA Food Safety Modernization Act, adding, "I think we need to look at that for meat and poultry and food under the USDA's jurisdiction as well."

Waldrop also welcomed the report's focus on Campylobacter. "That's sort of a new contribution to the discussion about which pathogens are causing which illnesses," he said. "Campylobacter is frequently not highlighted because it's typically not associated with outbreaks," with isolated cases more typical.

Further, he commented, "It's clear that Salmonella comes up several times in the pathogen-food combinations, and that again demonstrates that Salmoenlla is a problem we need to really focus on."

See also:

Emerging Pathogens Institute report page with links to policy brief and full report

March 17 CIDRAP News story on USDA standards for pathogens in poultry

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