Published February 11, 2004Alan Taege, MD |
Food-borne disease (FD) is a pervasive problem caused by consumption of contaminated food and drink. An estimated 76 million cases occur annually, resulting in 300,000 hospitalizations and 5,000 deaths.1 Far fewer cases are documented because of underreporting. The onset is generally acute, with resolution of the uncomplicated illness in 72 hours for most episodes. Proper food handling and preparation, personal hygiene, and improved methods of decontamination of consumer products could significantly reduce the extent of morbidity and mortality. FD can be caused by bacteria, parasites, toxins, and viruses (Table 1). Bacterial causes are common. Viruses are likely the most common cause but are seldom investigated and confirmed because of the short duration and self-limited nature of the illness. In addition, the inherent difficulty of laboratory investigation and subsequent cost of viral studies lead to a lack of clinician evaluation and therefore overall underreporting. Despite efforts to investigate FD, less than one half of all sources of outbreaks are identified. Food-borne illness is tracked in the United States through a system called FoodNet. This is a joint effort of the Food and Drug Administration and the United States Department of Agriculture. Data are collected annually from nine different monitoring sites throughout the country (representing 13% of the population) and compiled by the Centers for Disease Control and Prevention (CDC). Only documented cases are used for reporting. The target organisms include Campylobacter sp, Salmonella sp, Shigella sp, Listeria sp, E coli O157:H7, Vibrio sp, Yersinia sp, Cryptosporidium sp, and Cyclospora sp. The hemolytic-uremic syndrome is also tracked. An extensive overview of food-borne illness can be found on the CDC website.2 This site reviews many of the common syndromes in an educational case scenario format. Several useful tables list etiologic agents, incubation periods and major manifestations. Cultural, demographic, and travel factors have resulted in major epidemiological shifts in FD during recent decades.2 Previous outbreaks of FD were smaller and limited in scope, more often originated in the home, and were associated with Staphylococcus sp or Clostridium sp. Family picnics or dinners and home-canned foods were the typical sources for the outbreaks. Today, many more people dine outside the home and travel more extensively. As a result, 80% of FD occurs from exposure outside the home. Technology has provided the means for mass production and distribution of food. Therefore, FD often occurs on a massive scale whereby hundreds or thousands are exposed and may become ill. Mobility and travel have resulted in exposure to exotic foods in distant lands, transportation of these foods home, and subsequent exposure of family and friends. In addition, foreign visitors may unknowingly be incubating food-borne infections when they arrive in this country. Because of consumer demand, many nonseasonal foods are imported for resale and consumption. The production conditions are often not well controlled, and contaminated foods are imported. FD is more likely to affect the extremes of age as well as immunocompromised patients and pregnant women. These groups suffer a higher morbidity and mortality.3,4 The effect of FD may extend beyond the immediate illness as shown by a recent Danish study, which demonstrated a greater than threefold risk of dying in the year after having had a food-borne illness.5 The most commonly identified pathogens are Campylobacter sp, Salmonella sp, Shigella sp, and E coli O157:H7. These organisms are evolving with greater cold, heat, and acid tolerance as well as resistance to multiple antibiotics. Increased drug resistance has been associated with an increased risk of hospitalization.6 Unique ethnic food preferences and preparation have been associated with several food-related illnesses. One example is the African American tradition of chitterlings (cooked swine intestines) during the Christmas holiday season.7 This was recently associated with an outbreak of Yersinia enterocolitica in infants.8 Fresh cheese made from unpasteurized milk has been associated with episodes of Listeriosis in the Hispanic culture. Most FD has a short duration of illness and a self-limited course. However, some FD is associated with long-term chronic sequelae (Table 2). Salmonella, Shigella, Yersinia, and Campylobacter species are linked to reactive arthritis, and Campylobacter has been associated with the Guillain-Barré syndrome.9 Nearly any food can be a source of FD. Some foods are more commonly associated with particular organisms (Table 3). Salmonella has traditionally been associated with eggs, Campylobacter with chicken, and E coli O157:H7 with ground beef. A recent E coli O157:H7 outbreak was associated with steak that had been needle-tenderized, thereby exposing the center of the meat to surface organisms. If the steak is not thoroughly cooked to an adequate internal temperature, the organisms will not be destroyed and illness may occur. Incubation periods of various FD may yield clues to the etiology. Four categories can be envisioned, with very brief, short, intermediate, and long durations of incubation. The very brief category (<8 hours) is generally caused by preformed toxins. Short incubation periods (24 to 48 hours) are more typical of viral etiologies. Intermediate incubation periods (1 to 5 days) may correlate with many of the bacterial pathogens. The long-duration incubation group (>5 days) roughly correlates with parasitic infections. These rules of thumb are only rough parallels and include areas of overlap. In addition, the burden of organisms ingested may influence the incubation period and the rapidity of onset of illness, eg, a large inoculum may cause a shortened time to onset of illness. Bloody diarrhea or a febrile illness is often associated with invasive organisms. The more common etiologies of these clinical manifestations are listed in Table 4. Most FD is self-limited and requires only supportive care. The very young, the elderly, immunocompromised patients, and pregnant women may benefit from antibiotic treatment for bacterial or parasitic infections. Examples will be discussed in the individual which follow. |
Specific BacteriaParasitesToxinsVirusesReferences |
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Salmonella: The most recent FoodNet data listed nontyphoidal Salmonella as the most commonly identified bacterial cause of FD in 2002.10 Fever, abdominal cramps, and diarrhea (occasionally bloody) are the usual presenting symptoms after 1 or 2 days of incubation. Although generally self-limited, Salmonella infection may cause sepsis and localized infections, eg, septic arthritis and infection of endovascular prosthetic devices. The most common serotypes are Salmonella enteritidis and Salmonella typhimurium. Eggs are still a very common source because of vertical transovarial transmission within an infected poultry flock. Fruits, vegetables, meats, and ice cream are other reported sources. Populations at greatest risk are typically infants, the elderly, and the immunocompromised but also those with inflammatory bowel disease, hemoglobinopathies, and endovascular prosthetic devices. Antibiotic treatment should be considered for these high-risk groups. Unfortunately, increasing resistance to the usual antibiotics (cephalosporins, aminoglycosides, and fluoroquinolones) has made therapy more challenging. Campylobacter: Campylobacter is the second most commonly identified organism in FD. Acute dysentery ensues after a 2- to 5-day incubation period. Nearly two thirds of patients will have fever, and one half will have bloody diarrhea. Illness may last 1 week and then resolve spontaneously. Immunocompromised patients may experience a life-threatening sepsis. Young males are more often affected because of poor food handling knowledge. Virtually all human illness is caused by one species, Campylobacter jejuni. Poultry is the overwhelming source. Additional food sources include raw milk, water, and ice cream. When needed, a macrolide or fluoroquinolone antibiotic can be utilized in treatment, but once again increasing drug resistance may present a therapeutic challenge. Guillain-Barré syndrome may be an unusual sequela of infection with Campylobacter. Shigella: Although less common than Salmonella or Campylobacter, Shigella is a significant cause of FD. After 2 to 4 days of incubation, it produces a dysentery syndrome that often includes fever and bloody diarrhea. Duration is typically 5 to 7 days. Fruits, vegetables, and shellfish are frequent food associations. Third-generation cephalosporins and fluoroquinolones are the antibiotics of choice; however, drug resistance may be encountered. Escherichia coli O157:H7: E coli O157:H7 was initially associated with ground beef. Multiple other food associations have been noted such as unpasteurized apple cider, milk, juices, and lettuce. In addition, E coli was associated with non-food-borne illness after contact with cattle and swimming in contaminated lakes. Crump et al described an outbreak among a group after they visited a dairy farm.11 An estimated 60,000 to 70,000 cases occur annually, resulting in approximately 2,000 hospitalizations and 60 to 70 deaths. The average incubation period is 4 to 8 days. Then abdominal cramps occur with bloody diarrhea but little or no fever. The diarrhea usually resolves within 1 week. Antibiotics appear to have no role in treatment, as the illness is the result of a Shiga toxin produced by the organism. Five to 10 days after the diarrheal illness, the hemolytic-uremic syndrome may occur. It is more common in the young (<5 years old) and the elderly. Manifestations of HUS may include hemolytic anemia, thrombocytopenia, and acute renal failure. Neurological sequelae (i.e. seizures or stroke) may be additional late complications. Listeria: Listeriosis is a much less common cause of FD but has the highest hospitalization and mortality rates of all FD. It strikes more often at the extremes of age-in the young and elderly as well as in immunocompromised persons, causing a more severe illness in this population. Pregnant women are also at increased risk of infection. The manifestations appear to vary by host-related factors. The elderly and immunocompromised patients often manifest sepsis and meningitis whereas immunocompetent patients develop febrile gastroenteritis. Pregnant women may experience a flu like illness, but granulomatosis infantiseptica may affect the fetus, and the newborn may suffer bacteremia and/or meningitis. Data from the CDC suggest that Hispanic individuals may have a higher incidence of Listeriosis, especially Hispanic women of childbearing age and their infants.12 The reason for this finding is under investigation. Common associated foods include delicatessen meats, hot dogs, soft cheeses, and unpasteurized milk. An unpasteurized homemade soft cheese, queso fresco, has been associated with Listeriosis in the Hispanic population. Illness follows a 1- to 2-day incubation. Clinical symptoms include fever, gastrointestinal upset, and subsequent diarrhea. When treatment is needed, ampicillin appears to be the most effective drug. Vibrio: FD tends to be seasonal, with peak incidence in late summer and early autumn. Consumption of raw seafood from the southern United States seaboard is the most common food association. V parahaemolyticus and V vulnificus are the most frequently isolated species. They are halophilic and cold-tolerant organisms, making them more hardy and difficult to eliminate. A clinical syndrome of watery diarrhea, abdominal cramping, nausea, vomiting, and fever occur 1 to 4 days after ingestion. The illness is usually self-limited, with resolution in about 3 days. Persons with liver disease may develop a severe sepsis syndrome and/or bullous cellulitis with a very high mortality. Wound infections may also occur in fishermen and oyster shuckers. Appropriate antibiotic treatment includes tetracycline or ceftriaxone. Yersinia: Yersiniosis is an uncommon cause of gastrointestinal infection in the United States. It has been associated with the consumption of raw pork, unpasteurized milk and water, and the preparation, handling, or consumption of the ethnic food chitterlings. Young African American children are disproportionately affected. The incubation is 4 to 7 days and is followed by fever, abdominal pain, and bloody diarrhea. The abdominal pain may mimic appendicitis. Additional manifestations may include carditis, joint pain, or sepsis. Although most cases resolve spontaneously, severe cases may require therapy with doxycycline, fluoroquinolones, aminoglycosides, or trimethoprim/sulfamethoxazole. |
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Parasites are an uncommon form of food borne illness. Cryptosporidiosis and giardiasis have been associated with contaminated water. Cyclospora was most recently linked to imported raspberries. Trichinosis was traditionally linked to pork but has been contracted through other sources. Additional uncommon parasitic food borne illnesses include toxoplasmosis and amebiasis. |
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FD caused by toxins may have a variety of presentations that include gastrointestinal or neurological manifestations, or both. The preformed heat-stable enterotoxins associated with Staphylococcus aureus and Bacillus cereus have an acute onset of nausea, vomiting, and diarrhea within 1 to 6 hours of ingestion. Fever is not a common component of this self-limited syndrome. Symptoms generally resolve in 12 hours. Clostridium perfringens has a slower onset of illness. Occurring after approximately 12 hours because the heat-labile enterotoxin is produced in vivo after ingestion of the contaminated food. Cramping and diarrhea are the major manifestations, with resolution of symptoms in about 24 hours. Botulism produced by Clostridium botulinum occurs 18 to 36 hours after ingestion of the source food. Home-canned foods have been the sources traditionally involved. Nausea, vomiting, and diarrhea are followed by constipation; then a descending paralysis occurs. Antitoxins are available which can only prevent further progression of paralysis because they neutralize circulating toxin but have no effect on bound toxin. If the individual survives, it may require months for recovery. The onset of paresthesias within minutes to 1 hour of food ingestion should alert the clinician to the possibility of niacin, monosodium glutamate, fish, or shellfish poisoning. Scombroid poisoning (histamine fish poisoning) occurs as a result of the presence of histamine and inhibitors of histamine degradation in the flesh of the fish produced by marine bacteria. The fish most often associated with scombroid are tuna, mackerel, skipjack, bonito and mahi-mahi. The syndrome resembles a histamine reaction with flushing, headache, nausea, vomiting, cramping, and burning in the mouth and throat. Poisoning by ciguatera fish such as grouper and snapper produces nausea, vomiting, and diarrhea as well as paresthesias of the lips, tongue, and throat. Shellfish poisoning causes a similar syndrome except that muscle weakness, paralysis, or amnesia may occur in severe cases. Mushroom poisoning may produce a variety of clinical syndromes. Depending on the toxin involved, symptoms may range from parasympathetic hyperactivity to hallucination or hepatic and renal failure (in the case of amatoxins or phallotoxins). Onset is rapid, within 2 hours of ingestion, and resolution is in 24 hours. Organ failure may follow after an additional 1 to 2 days. |
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Hepatitis
A and Norwalk virus are the two most commonly identified viral sources
of FD. Many additional cases of FD occur as a result of unidentified viruses.
Hepatitis A is often associated with shellfish and infected food handlers.
The recent widespread outbreak of hepatitis A in restaurants, believed
to be from green onions, alerts us to additional potential sources.13 The recent epidemics of illness on cruise ships have been associated with
viruses as well. |
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