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Outbreaks and Surveillance |
Stopping Foodborne Illness In Its Tracks
Shortened outbreak response times are among the palpable payoffs from increased food safety resources. Thanks largely to a stronger surveillance system in recent years, outbreak detection has been quicker, investigation better coordinated, traceback more efficient and responses speedier.
Three food safety surveillance tools -- "PulseNet," "FoodNet" and the "National Antimicrobial Resistance Monitoring Network" (NARMS) -- played central roles in foodborne illness monitoring and prevention in FY 2000. Following are some of the year's highlights in terms of surveillance and outbreak response:
- FoodNet Reveals Promising Foodborne Illness Trends
Since 1995 when CDC, FDA and USDA put in place the collaborative FoodNet (Foodborne Disease Active Surveillance Network) system, the system has been a key tool for measuring the incidence and sources of bacterial foodborne diseases. An expanded FoodNet system has become an especially powerful network for monitoring the frequency of foodborne illnesses in the United States.
In FY 2000, the FoodNet project accomplished trend analyses of collected foodborne illness data that documented declines from 1996 to 1999 in the rates of the most common bacterial foodborne infections. The declines in foodborne illness were consistent with FDA's increased attention to "good agricultural practices" on farms; improved consumer education and, in turn, awareness about safe food practices; and additional interventions by FDA and other government agencies.
"These trends reflect a decrease in real consumers getting sick in their communities," says Wallace Garthright, Ph.D., Deputy Director of CFSAN's Division of Mathematics. By capturing clinical reports from about 10 percent of the U.S. population (specifically, from all or part of California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon and Tennessee), FoodNet can also reflect changes in the incidence of certain foodborne diseases in specific vulnerable populations such as children, the elderly, and those with compromised immune systems, Garthright says.
- Keeping Outbreaks Under Control: PulseNet's FY 2000 Role
Initiated several years ago by CDC, FDA and USDA's Food Safety and Inspection Service and managed by CDC, the PulseNet system was invaluable in FY 2000, helping the agencies to identify and control episodes of foodborne illness. The national laboratory network and computer database, which compares distinctive DNA "fingerprint" patterns of bacteria isolated from food, the environment, and people with foodborne illness using a molecular biology technology called "Pulsed-Field Gel Electrophoresis" (PFGE), received more than 17,000 pattern submissions in FY 2000, topping the previous year's totals by about 7,000.
| 1996 | 1999 | 2000 | 2001 | |
|---|---|---|---|---|
| # bacterial species | 1 | 3 | 4 | 7* |
| # participating labs | 10 | 35 | 54 | 64* |
| # FDA labs | 1 | 4 | 8 | 9* |
| # patterns submitted | 191 | 9,800 | 17,300 | 25,000* |
| * projected estimates | ||||
In FY 2000, the foodborne pathogen Shigella sonnei was formally added to the list of pathogens monitored by PulseNet. The number of public health laboratories doing routine subtyping, using PFGE, went up significantly for the other three PulseNet-analyzed foodborne pathogens, as well: E. coli 0157:H7 (40 labs in FY 2000, up from 29 in FY 1999), Salmonella (40 labs in FY 2000, up from seven in FY 1999), and Listeria monocytogenes (20 labs in FY 2000, up from seven in FY 1999). FDA has assigned resources at six regional laboratories to participate in this project.
"In these types of outbreaks, where the sicknesses can occur throughout the country, often a single health official would not be able to make a connection," says Farukh Khambaty, Ph.D., CFSAN's Project Leader for PulseNet. "PulseNet can act as an early warning system, helping to identify common-source clusters of DNA fingerprints to enable public health officials to trace an outbreak back to the source quickly." In addition to permitting rapid regulatory interventions, the system helps target the agency's limited inspection resources to foods and food processing practices that pose the greatest risk.
- FDA Keeps Close Watch on Drug Resistance Trends
FDA's Center for Veterinary Medicine (CVM), with CFSAN and other centers, continued in FY 2000 to monitor the emergence of drug-resistant pathogens. The agency relied, in part, on the National Antibiotic Resistance Monitoring System, or NARMS, a joint effort involving FDA, CDC and USDA that prospectively monitors when foodborne bacteria that can cause disease in humans begin to develop resistance to antimicrobials used in food animals. The following three CVM information-gathering initiatives were among the most notable in that year:
- FDA completed a quantitative risk assessment that modeled the human health impact of fluoroquinolone-resistant Campylobacter infections associated with consumption of chicken. The risk assessment showed that development of resistance in food-producing animals has an impact on human health by compromising the effectiveness of human medicines. The linkage shown in the risk assessment between fluoroquinolone resistance in chickens and a human health impact strengthens the scientific basis in considering future regulatory decisions, which would be developed through established notice-and-comment rulemaking procedures. Based on this risk assessment and NARMS data, FDA has already proposed, in FY 2000, to withdraw approval of the new animal drug application for the antimicrobial drug enrofloxacin for use in poultry, based on new evidence that the drug has not been shown to be safe for this use. Enrofloxacin belongs to the fluoroquinolone class of drugs, a class that is among the most valuable for treatment of human infections.
- In a first-of-its-kind international human and animal monitoring system for foodborne antimicrobial drug susceptibility surveillance in the Americas, FDA undertook a pilot study with Mexico in FY 2000 on a monitoring system for antimicrobial resistance in Salmonella. Preliminary findings from the pilot study, which was an outgrowth of NARMS, indicate a moderate carriage rate of Salmonella among healthy children in Mexico, but the isolates tended to be sensitive to all antibiotics tested.
- FDA, along with CDC, funded in FY 2000 two dairy research studies aimed at getting a better understanding of the issue of antimicrobial resistance. The first will study whether 30 dairy farms with at least a five-year history of zero or minimal use of antibiotics have lower rates of antibiotic resistance than conventional dairy farms that routinely use antibiotics. The second will study the effects of antibiotic use on antibiotic resistance in dairy cattle and will implement strategies for better control of antibiotic use, with the ultimate goal of minimizing the emergence of resistant bacteria on farms.