Preventive Medicine and Nutrition
Foodborne diseases are a serious and growing problem. Literature reports of the yearly incidence of foodborne illness range from 6.5 to 81 million people affected. The costs to patients, food producers, and the national economy is estimated to be $7.7 to $8.4 billion per year.1 The vast majority of cases, however, go unreported.
From 1973 to 1987, 7,458 outbreaks, involving 237,545 cases of food poisoning, were reported to the Centers for Disease Control and Prevention (CDC). Bacterial pathogens caused 66 percent of the outbreaks, 87 percent of the cases, and 90 percent of the fatalities. Approximately 50 percent of the outbreaks were caused by salmonella, mostly from beef and turkey.1
During this time period, three previously unrecognized foodborne pathogens emerged, including Campylobacter jejuni (associated with poultry products), Escherichia coli 0157:H7 (ground beef), and Listeria monocytogenes (dairy products). Other less common pathogens included Bacillus cereus, Clostridium botulinum, Clostridium perfringens (found in beef), Shigella, and Staphylococcus aureus (found in pork).1 In 1998, an estimated 8 million cases of foodborne illness occurred according to the CDC.
Escherichia coli 0157:H7 Outbreaks
In the early 1980s, Escherichia coli 0157:H7 began causing severe foodborne disease outbreaks. Before then, E. coli was considered a harmless inhabitant of the digestive tract of humans and animals. Today, the CDC estimates that there are 20,000 cases of E. coli 0157:H7 infection in the U.S. each year, associated with the consumption of contaminated beef, raw milk, and water.2 Infections are characterized by abdominal cramping and bloody diarrhea, and can progress to the hemolytic uremic syndrome (HUS), leading to kidney failure and sometimes blindness.3 Death rates from HUS range from 5 to 10 percent, but can be much higher in elderly people and children.4 The infection can also lead to neurological disease causing seizures, comas, and cerebral blood clots, and can so severely damage the lining of the large intestine that it may have to be removed to save the patient.2 E. coli 0157:H7 is a major cause of HUS in the U.S.,5 and HUS is most common cause of acute renal failure in children.3
The overall trend of E. coli infections is difficult to determine due to under-reporting by physicians, but it is estimated to be increasing. The incidence of HUS, which can be used as a marker for E. coli infections, is definitely increasing in the U.S.6 During January 1993, there were more than 230 cases of culture-confirmed E. coli infection in Washington state residents, causing four deaths. The infections were traced to undercooked hamburger.2
A 1987 study tested for the presence of E. coli 0157:H7 in supermarket meats. The bacteria was found in 3.7 percent of beef, 1.5 percent of pork, 1.5 percent of chicken and turkey, and 2.0 percent of lamb samples tested. These researchers suggested that “the organism is not a rare contaminant of fresh meats and poultry.”7
From 1987 to 1990, the Food Safety and Inspection Service (FSIS) found E. coli 0157:H7 in 2 out of 1,668 brisket and ground beef samples, and 8 out of 6,950 veal kidneys. These products were sold to consumers.
E. coli appears to be a common inhabitant of the bovine digestive tract. Studies from 1993 found the organism in 12 out of 50 dairy herds tested. Yet traceback systems to determine the source of infected meat are not in place, and routine tests for the presence of bacteria are not done in slaughterhouses or meat processing plants.
The proportion of bacterial outbreaks due to salmonella increased 130 percent between the two-year study periods of 1973 to 1975 and 1985 to 1987.1 Currently, about 45,000 salmonella isolates (cultures taken from sick patients) are reported to the CDC annually. These are associated with about 20,000 hospitalizations, 500 deaths, and medical expenses of at least $50 million. But the CDC estimates that only 1 to 5 percent of an actual 1 to 5 million salmonella infections are reported.3
Slaughter operations can spread contamination from one carcass to another. After defeathering, chicken carcasses are plunged into chill tanks, which can become quite dirty by the end of the day. A 1990 article in The Atlantic Monthly notes that the debris at the bottom of the tank may be one foot deep, and quotes an inspector who complained, “At the beginning of the day the chill-tank water is clear and clean, but as the day goes on, it becomes murky, dirty-brownish, and bloody.”8
From 1982 to 1984, one study found an incidence of 35.2 percent salmonella in chicken carcasses.9 From 1990 to 1992, FSIS found salmonella in 25 percent of broilers analyzed. Also studied by FSIS were 25-gram uncooked samples of beef (1.4 percent positive for salmonella), pork (4.8 percent), chicken (15.7 percent), and turkey (8.5 percent). These bacteria-infected samples were taken from products sold to consumers.
Other Foodborne Pathogens
During 1992, an FSIS survey was taken of cooked, ready-to-eat products for salmonella and Listeria monocytogenes. Products from 75 establishments were found to contain either salmonella or L. monocytogenes. Most of the infected products had been held, and the rest was recalled.
Campylobacter was the leading cause of foodborne illness in 1998, according to the CDC. These organisms readily colonize the avian intestinal tract but generally cause no illness in the bird.10 This means that infected birds are unlikely to be detected using the current methods of inspection in the slaughterhouse.
FSIS recently performed surprise inspections which serve to demonstrate how serious inspection problems are today. In May 1993, 90 beef slaughterhouses across the country were inspected without warning, and of those plants, 30 were temporarily closed due to noncompliance with federal inspection regulations, suggesting that new procedures will do no good if enforcement is not improved.
Since 1906, meat inspection has been limited to organoleptic methods, which rely on detecting changes in the sight, smell, or feel of the tissues. But this does not detect foodborne microorganisms. For the past several years, the National Academy of Sciences has recommended that a more complete inspection be instituted, which would include microbiological monitoring, since many contaminants could be present in numbers high enough to cause disease without altering the sight, smell, or feel of the carcass, or even without causing visible disease in living cows, pigs, or chickens.
FSIS reacted to foodborne outbreaks by instituting the Hazard Analysis and Critical Control Point program (HACCP) and began a microbiological baseline study of meat products called the Microbiological Baseline Data Collection Program. HACCP is a method of analysis designed to identify areas within the food processing chain where chemical or microbial contamination is likely to occur. Steps are then taken to alter the processing procedures at key steps, called critical control points, so as to reduce the possibility of foodborne disease or spoilage. Monitoring of the control points is performed by physical, chemical, or microbiological tests. However, the program is useless if the government is unwilling to mandate changes in plant operations. Slaughter line speeds, for example, contribute to contamination and make inspection more difficult. Yet producers and government regulations continue to sidestep this problem because slowing the slaughter line reduces profits.
In summary, microbial contamination of meat and poultry is a big problem, and it’s getter bigger. And with contaminated products in our kitchens and restaurants, cross-contamination and contagion will be increasing problems.
Cross-Contamination and Contagion: Persistent Dangers
Cross-contamination is a serious concern for the consumer, and its evaluation is critical in any discussion of meat safety. There are three ways people are exposed to pathogenic (disease-causing) bacteria. The first is through ingestion of contaminated products; the second through contact with persons already infected with the bacteria, which can be a particular problem in group settings such as nursing homes or day-care centers; and lastly, through ingestion of foods contaminated by contact with infected meat or contaminated utensils or kitchen surfaces.
Findings published in the February 1993 issue of the Journal of the American Medical Association described evidence of transmission of E. coli 0157:H7 from child to child in day-care centers, and suggested that household transmission may also occur.11
Since both E. coli and Shigella require only a small number of organisms to cause disease, and the infectious dose of salmonella is often low,12 cross-contamination becomes a major threat, and one that widens the scope of susceptible persons beyond those who eat undercooked ground beef and unpasteurized milk.
Even if bacterial contamination could be eliminated, meat should still not be considered a safe food, due to the long-term risks posed by its cholesterol and fat content, and its lack of fiber and complex carbohydrates. This combination is implicated in heart disease, various cancers, obesity, kidney disease, diabetes, hypertension, and other serious illnesses. Nonetheless, the acute risks of bacterial contamination are serious and often life-threatening, and have not been adequately addressed by the U.S. Department of Agriculture.
Federal authorities must set specific timetables and goals for dealing with food contaminants. To date, government efforts are inadequate.
The USDA seal of approval, which reas, “Inspected for wholesomeness, USDA,” should be dropped until federal food inspection authorities have developed and implemented a workable detection method for microbial contaminants.
Slaughter operations must have more inspectors, reduced line speeds, and comprehensive traceback systems that identify the sources of tainted meat. Federal authorities should begin the implementation of other recommendations already made by consumer groups to improve inspection procedures.
The federal government must require meat producers to withdraw pathogen-tainted meat from routine consumer use. Otherwise, detection is useless to the consumer.
Public education efforts must be stepped up to alert consumers to the risks from undercooked meat, cross-contamination, and contagion. Other consumer measures, such as simple cooking gauges on retail meat and poultry packages, should be considered.
Information on plant contamination levels, compliance, violations, and recalls should be released to the public.
Because the USDA has demonstrated that it is unable and unwilling to address food contamination issues, responsibility for food safety should be removed from them.
Health professionals should become familiar with E. coli 0157:H7 and the illnesses it can cause, and should test for the organism in all persons with acute bloody diarrhea.
State and federal regulations should require that E. coli 0157:H7 infection and hemolytic uremic syndrome (HUS) be reported to public health officials.
Imported meat should be subject to the same level of inspection as domestically produced meat.
1. Bean NH, Griffin PM. Foodborne disease outbreaks in the United States, 1973-1987: pathogens, vehicles, and trends. J Food Protection 1900;53(9):804-17.
2. Spencer L. Escherichia coli 0157:H7 infections forces awareness of food production and handling. JAVMA 1993;202(7):1043-7.
3. Potter ME. The changing face of foodborne disease. JAVMA 1992;201(2):250-3.
4. Siegler RL. Management of hemolytic uremic syndrome. J Ped 1988;112:1014-20.
5. Besser RE, Lett SM, Weber JT, et al. An outbreak of diarrhea and hemolytic uremic syndrome from Escherichia coli 0157:H7 in fresh-pressed apple cider. JAMA1993;269:2217-20.
6. Martin DL, MacDonald KL, White KE, Soler JT, Osterholm MT. The epidemiology and clinical aspects of the hemolytic uremic syndrome in Minnesota. N Eng J Med1990;323(17):1161-7.
7. Doyle MP, Schoeni JL. Isolation of Escherichia coli 0157:H7 from retail fresh meats and poultry. Appl and Env Micro 1987;53(10):2394-6.
8. Dirty Chicken. The Atlantic Monthly November 1990;266(5):32.
9. Green SS. Results of a national survey: salmonella in broilers and overflow chill tank water, 1982-1984. USDA, FSIS, 1987.
10. Hooper BE. Overview. JAVMA 1992:201(2):259-2.
11. Belongia EA, Osterholm MT, Soler JT, Ammend DA, Braun JE, MacDonald KL. Transmission of Escherichia coli 0157:H7 infection in Minnesota child day-care facilities. JAMA 1993;269:883-8.
12. Blaser MJ, Newman LS. A review of human Salmonellosis: I. infective dose. Rev Infect Dis 1982;4(6):1096-106