Foodborne illness levels off in past several years

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CDC report states overall progress stopped in 2004


Progress toward reducing infections from some pathogens has hit a plateau, indicating "fundamental problems with bacterial and parasitic contamination are not being resolved," a recent report states.

The Centers for Disease Control and Prevention released a Morbidity and Mortality Weekly Report April 10 indicating the prevalence of illnesses from nine foodborne pathogens has declined since the 1990s but remained level from 2004 through 2008. The report is available at

Those pathogens are Campylobacter, Cryptosporidium, Cyclospora, Listeria, Shiga toxin-producing Escherichia coli (STEC) O157, Salmonella, Shigella, Vibrio, and Yersinia.

The data are based on surveillance through FoodNet, which has monitored laboratory-confirmed infection data since 1996. The surveillance population is about 46 million people, and in that population were about 18,500 laboratory-confirmed cases in 2008 of infection with the nine previously listed pathogens.

The report notes none of the 2008 goals for reduction of foodborne pathogens were met under Healthy People 2010, an initiative launched by the Department of Health and Human Services in January 2000 to promote health and prevent disease. The initiative has 28 focus areas covering a broad range of human health issues, including food safety.

The Salmonella infection rate, at 16.2 cases per 100,000 people, is furthest from the Healthy People 2010 initiative goal of 6.8 per 100,000.

"The lack of recent progress toward the national health objective targets and the occurrence of large multistate outbreaks point to gaps in the current food safety system and the need to continue to develop and evaluate food safety practices as food moves from the farm to the table," the report states.

Finding the source
The CDC did not compile data that would indicate whether safety had improved among food animals or plants, spokeswoman Lola Russell said. The agency is recommending that actions be taken, and it is up to food safety regulators to decide how to respond.

Dr. John R. Dunn, director of Foodborne, Vectorborne, and Zoonotic Diseases for the Tennessee Department of Health and principal investigator for FoodNet in Tennessee, said better communication and partnership across public health and regulatory agencies could improve understanding of sources of food contamination and subsequent outbreaks. He noted an increase in the number of illnesses associated with produce in recent years.

"Many of these foodborne pathogens have some connection to an animal reservoir," Dr. Dunn said.

David Goldman, MD, assistant administrator for the Department of Agriculture's Food Safety and Inspection Service, said a Salmonella initiative started by his agency in 2006 has substantially reduced the bacteria's presence in raw meat and poultry products.

"We have worked hard to reduce contamination in FSIS-regulated products and have seen marked success in Salmonella and Listeria monocytogenes," Goldman said. "We are concerned about the lack of progress in reducing the incidence of foodborne illness and believe this report points to the need for better information about sources of infection."

David Acheson, MD, associate commissioner for foods at the Food and Drug Administration, sees a shift in the foods that have been associated with foodborne illness.

"We've seen a number of foods associated with outbreaks that we haven't seen before," Dr. Acheson said. "Peanut butter is a classic one where we've seen two big outbreaks in the last couple of years, which has never happened before in the United States."

Dr. Acheson noted jalapeño peppers, which were associated with a Salmonella outbreak in summer 2008, are also a new vehicle for illness.

Investigators are better at finding foodborne pathogens and their sources, Dr. Acheson said, but it was not clear if that fully explained why pathogens have recently been associated with different foods.

"It's hard to know whether we're just getting better at it or whether the landscape is changing," Dr. Acheson said. "It may be a combination of the two."

Dr. John P. Sanders, branch chief for food defense and preparedness coordination in the Department of Homeland Security's Office of Health Affairs, said the CDC has received more outbreak reports since switching from paper reports to the electronic Foodborne Outbreak Reporting System in 2001. The technology used to identify foodborne pathogens has also improved, and public awareness has increased.

Dr. Acheson noted some initial gains in food safety after FoodNet was started in 1996, and he agreed with the assessment that infection rates have leveled off among the major pathogens tracked through the service.

"What I take from that is we need a new approach," Dr. Acheson said. "We have got to be looking at learning from the controls that we've put in place—the systems we've put in place—because, obviously, there's been some effect from that, but it's no longer driving (rates) down further."

Dr. Acheson said cleanup of food processing equipment between runs of raw and roasted pistachios could have prevented contamination at a California factory. Though the factory was associated only with a recall and not an outbreak, he said the facility is useful as an example for control of food contamination.

It is likely that, as new measures are implemented, food safety will again plateau, Dr. Acheson said.

"But if you're on a winning streak here, you're going to plateau lower, and then you'll identify the next round of controls that you need to put in place, and you plateau even lower," he said.

Beyond the "low-hanging fruit"
Dr. David R. Smith, a professor and extension dairy and beef veterinarian for the University of Nebraska, said the reductions in foodborne illnesses prior to 2004 coincided with safety improvements in postharvest sectors of animal industries, particularly those related to beef cattle. The FoodNet data suggest to him that members of the animal agriculture industry have adopted some of the easiest measures to improve safety.

"The low-hanging fruit has been picked, and it's time to look at where else are there gaps in food and environmental safety," Dr. Smith said.

For example, Dr. Smith said little has been done to reduce carriage of E coli O157 or Salmonella in live cattle, which could also reduce environmental contamination of produce.

Veterinarians and the veterinary profession can also work to increase public awareness of the risks posed by zoonotic pathogens, Dr. Smith said.

Dr. Sanders said outbreaks of foodborne illness involving produce still tend to involve human or animal contamination of crops or irrigation water, and he cited as an example an E coli 0157:H7 outbreak associated with feral swine crossing a spinach field.

"Salmonellosis is a large proportion of our foodborne disease illness, so in that respect it's disappointing that we're not able to identify things that would create a sustained decline."



Dr. Sanders said such outbreaks have raised the awareness of Congress, and that could increase opportunities for veterinarians in public practice.

"Hopefully we will get some additional funding for the agencies that are involved in food safety, where this is an opportunity for them to become involved," Dr. Sanders said.

Though the FoodNet data do not indicate which food has become contaminated, they provide insight into the volume of illnesses in the United States. Dr. Acheson likened FoodNet reports to report cards and said they are valuable for regulatory agencies.

Some changes are evident in the incidence of pathogens, as seen in a substantial decline in E coli O157-related illnesses several years ago, Dr. Dunn said. The incidence has not substantially declined since, and opportunities exist for veterinarians interested in research related to the bacteria and food safety.

"With the integration of veterinarians at all levels of food safety—from the preharvest aspects that I mentioned all the way through to the end that I work on, which is the identification of illness and investigation—veterinarians have contributed greatly, and there's ample opportunity to continue to address this problem of foodborne illness for veterinarians," Dr. Dunn said.

Veterinarians involved with public health and livestock can serve as consultants for farms and feedlots and minimize the impacts they have on surrounding produce farms, Dr. Sanders said. The FDA has been working with Cornell University and the University of Maryland on the Good Agricultural Practices program to educate farmers about their impact on food safety.

The DHS, USDA, and FDA are also working to improve abilities to detect harmful agents in food, Dr. Sanders said. The DHS is also working with state and local health departments to help them stabilize their funding and focus on food protection.

Dr. Dunn said that, despite improved ability to measure incidence of Salmonella since the advent of FoodNet, the data do not show a sustained decline in salmonellosis.

"Salmonellosis is a large proportion of our foodborne disease illness, so in that respect it's disappointing that we're not able to identify things that would create a sustained decline, particularly in salmonellosis," Dr. Dunn said.

A CDC report from April 2005 indicates substantial declines from 1996-2004 in the estimated incidence of infections with Campylobacter, Cryptosporidium, STEC O157, Listeria, Salmonella enterica serovar Typhimurium, and Yersinia. Similar to the 2009 report, the 2005 report called for efforts to understand and control pathogens in animals and plants, reduce or prevent contamination during processing, and educate consumers. The CDC posts an annual summary report on the FoodNet surveillance, and as of press time, the last full report available online involved data from 2004.

– Greg Cima



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