May 10, 2012 (CIDRAP News) – In a special journal supplement today, federal officials reported that progress is slowing in the battle against the six most common foodborne diseases, among a raft of other findings.
Health officials typically issue a foodborne illness "report card" each year, based on the latest surveillance data, but this year researchers who study the diseases provided a more varied and detailed look at the trends. The US Centers for Disease Control and Prevention (CDC) published 18 reports in a Clinical Infectious Diseases (CID) issue that addresses trends, illness sources, pathogens, and testing.
The studies are based on the Foodborne Diseases Active Surveillance Network (FoodNet), a system the CDC uses to gather information on confirmed foodborne illnesses from 10 states or parts of states.
Barbara Mahon, MD, MPH, deputy chief of the CDC's enteric diseases epidemiology branch, said in a statement that the agency pulled together the supplement to dig into important issues that go beyond its annual reports.
"We're excited about these detailed analyses of a decade or more of surveillance data on important foodborne pathogens—as well as on several key scientific issues related to conducting high-quality surveillance—because we think they offer important insights for saving lives and protecting people from foodborne illnesses," she said.
In an editorial introducing the supplement, Mahon and Elaine Scallan, PhD, with the department of epidemiology at the Colorado School of Public Health, wrote that the reports are designed to help prioritize and evaluate food safety interventions and monitor progress toward meeting national health goals.
For example, in one of the studies, CDC researchers explored the overall change in illness incidence caused by six bacterial pathogens tracked by FoodNet from 1996 through 2010: Campylobacter, Listeria, Salmonella, Escherichia coli O157, Yersinia, and Vibrio. They found that the overall incidence dropped 23% over the time frame, though the pace slowed to a 3% decrease between 2006 to 2008 and 2010.
In a study that profiled Salmonella Enteritidis infections since 1996, researchers from the CDC and several of their state partners compared FoodNet data with passive surveillance findings and rates of pathogen isolation from processed chicken and egg products. They found that the incidence of human infections has climbed 44%, led by illnesses in older people, children, and patients in southern FoodNet sites.
The proportion of infections related to international travel has dropped, while the levels isolated from chickens have been rising, which led the group to conclude that most Salmonella Enteritidis infections in the United States are linked to domestic sources, most likely chicken and eggs.
Another group, including officials from the CDC and their colleagues from six different states, analyzed zoonotic links to foodborne illnesses and found that 14% of the seven most common foodborne diseases have links to contact with animals, with Campylobacter, nontyphoidal Salmonella species, and Cryptosporidium species as the top three pathogen types.
Certain interactions are more likely to result in pathogen transmission, such as contact with livestock, the group noted. Because live poultry is a reservoir for nontyphoidal Salmonella species, buying ducklings and chicks in the spring as pets for children poses a transmission risk, as does the increasing popularity of keeping backyard flocks of chickens, the researchers wrote.
Recent outbreaks linked to dry dog food and reptile food underscore the importance of educating the public about proper food handling and hand washing routines, the investigators emphasized.
Some researchers explored foodborne illness patterns in specific demographic groups. A team that looked at gender differences in food consumption found that men are more likely to eat "high-risk" food such as undercooked hamburger, raw oysters, and undercooked eggs.
On the other hand, women were more likely to eat vegetables and fruits. They found that only one high-risk food was consumed more often by women: alfalfa sprouts.
A research team that explored patterns in international travelers found that Campylobacter is the most common cause of foodborne infections, with over half of the illnesses acquired in Latin America and Caribbean countries. However, they found that travel to Africa posed the greatest risk of travel-associated infections.
When researchers tracked patterns with Yersinia enterocolitica infections from 1996 through 2010, they found a notable decrease, led by a drop in illnesses in black children from Georgia. They said the decrease may have resulted from intensive educational campaigned aimed at safe handling and consumption of chitterlings, especially around the holiday months.
Another team found that the pace of vibriosis increased over the same time period, which they said suggests a need for better efforts to educate the public about the risks of eating raw seafood and decrease contamination in oyster beds.
Some of the studies have implications for clinical practice. For example, an analysis of 955 responses to a physician survey found that overall knowledge of Shiga toxin–producing E coli infections was low, and those who had more knowledge were more likely to interpret lab test results correctly.
A study that used FoodNet data and information from the National Antimicrobial Resistance Monitoring System (NARMS) found high levels of antibiotic resistance to Shigella isolates. The team concluded that it's important to look at susceptibility patterns before starting treatment for shigellosis.
Jun 1 Clin Infect Dis FoodNet supplement
May 10 CDC media advisory on the supplement
Mahon and Scallon editorial
Study abstract on FoodNet data, 1996 through 2010
Salmonella study abstract
Animal-linked foodborne disease study abstract
Study abstract on sex-based differences
Travel-related foodborne disease study abstract
Yersinia enterocolitica study abstract
Vibriosis study abstract
Study abstract on physician knowledge
Shigella study abstract