Foodborne and Waterborne Illness
Foodborne and waterborne illnesses are common but often unrecognized. They cause an estimated 48 million illnesses, 128,000 hospitalizations, and 3,000 deaths yearly in the US. The most prominent symptoms are nausea, vomiting, and diarrhea, but the associated dehydration may lead to electrolyte irregularities, acute renal failure, and encephalopathy. Rarely, food or waterborne illness may be associated with prolonged or more severe complications, such as anemia, shock, hemolytic-uremic syndrome, spontaneous abortion, seizures, and liver, heart, or lung disease. Many illnesses carried by food or water are particularly common in the developing world, due to poor sanitation, polluted water, and lack of refrigeration. However, developed countries are by no means exempt. About 20% of all US diarrheal episodes are believed to be caused by foodborne or waterborne illness.
This chapter focuses mainly on acute diarrheal illnesses but also includes information on prions and other rare diseases that are part of the full scope of foodborne and waterborne illness.
Risk factors for specific pathogens are presented below.
Weakened immune system. Infants, elderly people, individuals taking immune-modulating drugs, and those with chronic diseases are at increased risk.
Improper food handling or storage. Food should be kept at proper hot or cold temperatures to reduce bacterial growth. Additionally, undercooked foods, raw meats, and unpasteurized products carry high risk of microbial contamination. When preparing food, care should be taken to avoid cross-contamination in which potentially infectious foods or infectious surfaces (cutting board, knife) come in contact with ready-to-eat foods.
Hygiene. Spread of disease is facilitated by environments where raw sewage, from either humans or animals, contaminates water used for drinking or irrigation. Infected food handlers may contaminate food during preparation after inadequate hand washing. Child daycare facilities are common sources of infection, as hand washing may not be sufficiently thorough.
A detailed history to assess symptoms and temporal relationships with exposures to food, sick persons, or travel (including hiking and camping) is important. The history may help determine whether the condition is likely to be self-limited or requires treatment. In addition, the history points toward likely causative organisms that may be candidates for testing. For example, a history of blood or mucus in the diarrhea may warrant stool examination and direct visualization of the colon. Laboratory evaluation is not indicated for most cases of acute vomiting or diarrhea. In patients who appear dehydrated, it is important to monitor electrolytes and renal function. In individuals with severe illness, a complete blood count, blood cultures, and stool studies may be useful. Stool studies include stool culture, leukocyte count, and fecal occult blood testing. Clinicians should screen for ova and parasites if diarrhea has persisted longer than 1 week. While not a foodborne illness, Clostridium difficile infection should be in the differential of acute diarrhea among patients who have recently used antibiotics.
Acute diarrhea diagnosis in the clinical setting is based on an increased frequency and looser consistency of stools. The criteria for severe illness are > 6 stools in 24 hours, fever, or symptoms of volume depletion. In most cases, antibiotics are not indicated, and may worsen the patient’s condition, either prolonging diarrhea (antibiotic induced diarrhea) or initiating hemolytic uremic syndrome if the patient is infected with E coli O157:H7. In cases of salmonellosis, antibiotics may result in a chronic carrier state in the gallbladder.
Irritable bowel syndrome, inflammatory bowel disease, malabsorption syndromes (e.g., celiac sprue, gluten, and other food intolerances), and hyperthyroidism should be considered in the differential if the diarrhea does not resolve within 1-2 weeks.
Viral gastroenteritis. Norovirus is the most common cause of infectious gastroenteritis and may cause vomiting and explosive diarrhea. It occurs in families and among persons living in other close quarters, such as cruise ships and daycare settings. Viruses can be transmitted through the air and via the fecal-oral route. Rotavirus, adenovirus, and astrovirus are other common viral causes of intestinal illness.
Salmonella. This widespread foodborne illness occurs in 2 main types: typhoid fever and nontyphoidal infection. Typhoid fever classically presents systemically with fever, hepatomegaly, and splenomegaly, and a tender abdomen, but it may also include rash (i.e., a classic “rose spot” skin lesion) and diarrhea or constipation. Nontyphoidal salmonella infection typically presents with nausea, vomiting, diarrhea, and fever and is the most common bacterial cause of foodborne gastroenteritis in the US. Illness usually occurs due to undercooked poultry, cross-contamination of other foods or cooking surfaces, raw or undercooked eggs (including egg-containing products, such as mayonnaise and custards, left at room temperature) and unpasteurized juices and dairy products.
Milk, meat, and fecally contaminated fresh produce, such as alfalfa sprouts, may also transmit disease, as can pet reptiles such as turtles. Disease occurs more commonly in the summer and fall. Particularly susceptible are individuals with inflammatory bowel disease, lymphomas, and altered bowel flora (e.g., due to antibiotics). Bloody diarrhea may occur.
Carriers of Salmonella typhi (e.g., the infamous cook “Typhoid Mary” in early 20th century New York) occasionally cause typhoid fever epidemics.
Campylobacter. The second most common cause of foodborne illness in the US is Campylobacter jejuni. Undercooked poultry, unpasteurized dairy products, and cross-contamination of other foods are the most likely sources. On average, 60% of retail poultry products throughout the world and up to 88% in the US are contaminated with campylobacter. , Bloody diarrhea may also occur with campylobacter infection.
Shigella. The third most common cause of foodborne illness in the US are shigella species. These bacteria are highly infectious (an inoculum of just 10 organisms can cause infection), since they can withstand gastric hydrochloric acid. They are spread through food, water, or person-to-person contact. It is common in nursing homes and daycare settings. It often causes bloody diarrhea. Other complications include hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Shigella dysenteriae is found in underdeveloped countries and may result in bloody diarrhea and shock.
Cryptosporidium parvum. This parasite is transmitted through ingestion of C parvum eggs in contaminated or inadequately filtered water, or exposure to cows and their manure. In addition to being a common water contaminant, it can contaminate produce and unpasteurized milk. Cryptosporidium is a common infectious agent in pools and spas and can also spread from person to person. Self-limited diarrhea is common in immunocompetent individuals. In persons with HIV, diarrhea can be chronic and debilitating.
Escherichia coli. The E coli O157:H7 strain is spread most often through undercooked hamburger. Unpasteurized juice and raw produce contaminated by cattle manure may also be sources. It may cause bloody diarrhea and can lead to the hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Like salmonella, it usually occurs in the summer and fall. Other more common E coli strains may also cause diarrheal illness.
Yersinia enterocolitica. This bacterium may produce pharyngitis, abdominal pain and diarrhea, and typically comes from undercooked pork, unpasteurized milk, or contaminated water.
Vibrio cholerae. This often severe bacterial infection results in a secretory diarrhea. It occasionally occurs along the Gulf Coast from contaminated water. Vibrio parahaemolyticus and vulnificus infection is due to ingestion of contaminated shellfish, and may cause sepsis and shock in patients with advanced liver disease.
Cyclospora cayetanensis. This parasitic infection is acquired from produce exposed to contaminated water and person-to-person contact. It may cause prolonged diarrhea, upper gastrointestinal symptoms, and systemic symptoms, such as fatigue.
Bacillus cereus. This bacterium can multiply in underheated foods, such as rice, sauces, gravies, or foods left under heating lamps at suboptimal temperatures. B cereus produces toxins that typically cause rapid-onset, self-limited vomiting and may also cause diarrhea.
Staphylococcus aureus. Ingestion of toxins produced by S aureus may cause symptoms similar to those caused by B cereus within 6-10 hours. Common sources include contaminated salads, eggs, meat, and dairy products that have been prepared and left at room temperature.
Clostridium perfringens. Found in contaminated meat and poultry, it produces toxins after ingestion.
Giardia lamblia. This very common intestinal parasite is often found in mountain streams due to fecal contamination by beavers and bears. It is also spread through food and person-to-person (fecal-oral) contact, and causes upper gastrointestinal symptoms, along with diarrhea and foul-smelling flatulence.
Entamoeba histolytica. An infection occurring worldwide, it is prevalent in tropical regions. In addition to causing painful profuse diarrhea with blood and mucus, amoebic infection may also cause ulcers on the anus, and liver, lung, heart, and brain abscesses with systemic symptoms. It can be transmitted sexually, as well as by consumption of contaminated water.
Hepatitis A. This virus can be contracted through water, contaminated produce (e.g., strawberries and cantaloupe), milk, and raw shellfish. Spread usually occurs through cross-contamination by an infected food handler, particularly one who does not practice good hand washing, at any point from the farm to the plate. Fecal-oral transmission may also occur through sexual contact.
Listeria monocytogenes causes listeriosis and is fatal in nearly 20% of cases. The most common manifestations include bacteremia and meningitis, particularly in infants and the elderly. This organism is the basis for the warning to pregnant women not to consume unpasteurized soft cheeses, particularly from Latin America. Raw hot dogs, cole slaw, and deli meats are also high-risk foods. Less commonly, one may develop gastroenteritis related to listeriosis. Immunocompromised patients, particularly renal transplant recipients, are at increased risk for listeriosis.
Clostridium botulinum causes a life-threatening paralysis and may result from home canning, fish fermentation, and extended use of food warmers. Infants less than 12 months of age may develop life-threatening botulism from ingestion of spores present in honey or corn syrup. These products should not be used in this age group.
Toxoplasma gondii i nfection may occur through ingestion of raw beef or lamb or through cross-contamination from cat feces (e.g., in infrequently cleaned litter boxes and gardens). Infection is generally self-limited and asymptomatic, except in immunocompromised patients. However, primary infection with toxoplasmosis during pregnancy is dangerous to the fetus. Immunocompetent individuals may develop a mononucleosis-like syndrome. In individuals with T-cell immunodeficiencies, such as HIV patients or heart transplant recipients, the organism often causes brain, retinal, lung, and muscle lesions (commonly due to reactivation of previous infection, rather than new infections).
Trichinosis. This disease is caused by ingestion of encysted larvae in undercooked pork and wild carnivorous game, such as bear. Cattle and horse meat can be cross-contaminated. Trichinosis rarely causes diarrhea but may cause ocular, cardiac, neurologic, and muscular symptoms such as muscle swelling and pain after larval migration. It is now rare in the US due to regulatory controls on the feeding of pigs, but is seen more commonly in developing countries.
Echinococcus. This parasite may be ingested in water contaminated by wild and domestic canines (e.g., foxes and wolves), particularly in the Middle East, Greece, Africa, and Asia. Cysts may infect the liver and lungs and may cause symptoms decades after the initial infection.
Brucellosis. Brucellosis, particularly B abortus, B melitensis, and B suis, is found in contaminated dairy and meat products, commonly from Latin America. Brucellosis may result in high fevers, septicemia, septic arthritis, meningitis, endocarditis, osteomyelitis, and rashes.
Tapeworms can be found in raw fish, beef, and pork. Taenia solium may be acquired through ingestion of infected raw pork or soil, resulting in cysticercosis or neurocysticercosis. With neurocysticercosis, patients will commonly present with new-onset seizures, even after death of the parasite. Migration to the skin and liver may also occur. In rare instances, fish tapeworms may cause pernicious anemia due to vitamin B 12 malabsorption. Beef tapeworms are asymptomatic.
Fish toxins cause several kinds of illness. Ciguatera poisoning occurs after ingesting fish that have eaten toxic microalgae. It is associated with neurologic and cardiovascular complications, including circumoral paresthesias and paralysis. Scombroid, or histamine poisoning, results from the bacterial decomposition of muscle proteins of certain finfish (e.g., tuna and mackerel). Tetrodotoxin in puffer fish is often fatal due to multiorgan system collapse.
Prions are abnormal proteins that cause slowly progressive spongiform encephalopathies, including Kuru, Creutzfeldt-Jakob disease, and bovine spongiform encephalopathy (BSE, or “mad cow disease”). The latter disease emerged in the mid-1990s in Great Britain, presumably due to the practice of feeding cattle the remains of other ruminants, particularly sheep. (Sheep are susceptible to a similar spongiform encephalopathy called scrapie.) Evidence suggests that human cases of variant Creutzfeldt-Jakob disease have been due to prion transmission through consumption of infected cattle. The risk to humans has been reduced by regulations for livestock feeding and processing that help prevent ingestion of concentrated neural material (i.e., brain and spinal cord). Similar diseases occur in other animals, such as chronic wasting disease in deer and elk.
Prevention and Treatment
Prevention is the most effective way to limit the morbidity and mortality associated with food and waterborne illness. Essential to prevention efforts are clean drinking water, restaurant and meat inspection, temperature monitoring, appropriate sewage processing, monitoring of public waterways for contamination, and public education on proper hygiene. The public should be cautioned about foods presenting particular risk and given instruction in proper food handling and preparation.
Vaccines are available for hepatitis A and typhoid fever.
All patients with suspected foodborne illness should be instructed in proper hand-washing techniques to protect others with whom they are in contact. Diagnosis of foodborne illness generally requires notification of the public health department.
Most acute diarrheal episodes are self-limited. Oral (or intravenous) rehydration therapy (ORT) may be needed. Patients treating their conditions at home can prepare ORT using 1 teaspoon of salt, 1 teaspoon of baking soda, and 8 tablespoons of sugar mixed in 2 liters of clean water. Some outcomes may be improved or the disease course shortened through antibiotic treatment, but only when a specific diagnosis is suspected. Antimotility drugs (e.g., loperamide) may be useful in viral diarrhea, or when easy access to a restroom is limited, but are otherwise not generally recommended.
Note: Travelers may use ciprofloxacin (500 mg twice daily) or azithromycin (1 gram) in case of severe diarrhea. Therapy may be needed for 3 days if not resolved in 24 hours. Bismuth subsalicylate may also be used (using an equivalent of 524 mg every 30 minutes as needed up to 8 doses/24 hours). Toxicity is possible, especially in aspirin users, and manifests as tinnitus and vertigo. Additionally, large doses can be neurotoxic. Anti-motility agents should generally be avoided, if possible, in those with typical traveler’s diarrhea. If used, they should be administered in conjunction with aforementioned antibiotics.
Salmonella (nontyphoidal) is usually self-limited, although antibiotic treatment should be used in very sick individuals, such as those with concurrent immunocompromised states or vascular disease or at the extremes of age.
Typhoid fever may be multidrug resistant. Resistance varies according to the country of exposure.
Campylobacter may be treated with antibiotics, which may shorten the duration of illness, but are not usually required. Typically, fluoroquinolones, macrolides, and aminoglycosides are effective. However, many studies have verified growing resistance to fluoroquinolones.
Shigella, like salmonella and campylobacter, is treated with antibiotics when patients are very sick, immunocompromised, or a risk to public health (i.e., food handlers, daycare attendees, hospital workers). Antibiotic choice depends on the age of the patient and resistance patterns. Typical antibiotics are fluoroquinolones, trimethoprim-sulfamethoxazole (if sensitive), cephalosporins, and azithromycin. Ceftriaxone is used in children.
Cryptosporidiosis treatment is rarely necessary in immunocompetent persons. In immunocompromised patients, such as those infected with HIV, nitazoxanide has been used with varying success. Additionally, paromomycin, with or without azithromycin may be effective, but data are sparse.
E coli (O157:H7) should generally not be treated with antibiotics, as their lack of efficacy is well-documented and treatment has been linked with a higher incidence of hemolytic uremic syndrome. Other E coli infections may require supportive therapy. Traveler’s diarrhea is often caused by non-O157:H7 E coli species (see above).
Yersinia requires antibiotics in complicated illness only.
For vibrio infections, oral rehydration therapy is essential due to the risk of severe diarrhea resulting in volume loss and shock. Antibiotics may shorten the course of diarrhea and vibrio excretion, and may be used as a therapy adjunct. Macrolides, doxycycline, and fluoroquinolones are possible choices. Macrolides are commonly used for children. For children with severe diarrhea, vitamin A and zinc supplementation are important treatment measures. Mortality can exceed 50% when vibrio infections are untreated.
Listeria should be treated promptly with intravenous antibiotics, such as ampicillin, penicillin G, gentamicin, or trimethoprim-sulfamethoxazole. A 2-week treatment is generally prescribed, except in immunocompromised patients, for whom longer courses are required. Gentamicin is used or added to ampicillin therapy if central nervous system infections or endocarditis are suspected or confirmed. Additionally, ampicillin and gentamicin are used together for empiric treatment of neonates.
Botulism requires hospitalization for monitoring of respiratory failure. If botulism is highly suspected, treatment with an equine antitoxin is indicated for all individuals greater than 1 year of age. Infants are treated with human immunoglobulin. For wound botulism antibiotics may be used, although trials do not provide consistent evidence for support of this therapy. Antibiotics should not be used for foodborne botulism as they can increase the release of toxin. Enemas and laxatives are helpful for foodborne botulism.
Toxoplasma gondii infection should be treated in pregnant and immunocompromised patients or in the presence of severe or prolonged symptoms. Pyrimethamine and sulfadiazine (folic acid antagonists) are the drugs of choice, along with folinic acid to prevent sulfadiazine-associated bone marrow suppression.
Cyclospora can be treated with trimethoprim-sulfamethoxazole.
Tapeworms can be prevented by cooking or freezing meat prior to ingestion and by avoiding cross-contamination. Praziquantel should be used for confirmed infections. Anticonvulsants are required in the rare incidence of seizure activity.
Amoeba and giardiasis may be treated with metronidazole.
Echinococcus treatment options include surgery, percutaneous treatment (drainage), drug therapy with albendazole or observation depending on the stage of disease. Spillage of cyst contents into the peritoneal cavity may result in anaphylaxis; therefore, expertise with this procedure is required.
Trichinosis can usually be prevented by freezing meat. For individuals who consume pork or other at-risk meats, thorough cooking also kills these pathogens. Treatment is not usually necessary, but mebendazole and albendazole are generally effective. Symptomatic treatment of pain and fever and systemic steroids are often helpful. Systemic steroids are useful in severe cases.
Brucellosis is related to unpasteurized dairy products and contact with animals on farms or in slaughterhouses. Infections are commonly treated with a regimen of doxycycline plus rifampin, gentamicin, or streptomycin.
Foods of animal origin, particularly meat and eggs, are most often implicated in cases of foodborne illness worldwide. Scientists at the Center for Disease Control and Prevention’s (CDC) Foodborne and Diarrheal Diseases Branch have observed that foodborne illness commonly starts with contamination of animal feed with Salmonella enterica. , Other investigators working with the Food and Drug Administration’s (FDA) Division of Animal and Food Microbiology Office have documented that resistant strains of salmonella are common in retail ground meats, including ground chicken, beef, turkey, and pork.
Consumers may believe that choosing white meat in place of red meat will reduce their risk for foodborne infection. However, a multistate investigation linked an outbreak of listeria to processed turkey meat, resulting in a recall of 16 million pounds of the product. In addition, pork sausage production plants have been repeatedly reported to carry Listeria monocytogenes—a persistent pathogen that requires strict hygienic measures to prevent all stages of its microbial growth. Eating chicken from restaurants has been noted as a common cause of infection with campylobacter, a bacterium that is a common cause of gastroenteritis in the US. Broiler chicken producing states are noted to have greater campylobacteriosis incidence rates than states without broiler operations, likely attributed to the pathogen spreading in the surrounding environment (i.e., in contaminated water bodies, agricultural manure, and application runoff).
Raw oysters and other shellfish eaten by approximately 10% of adults each year may be a source of vibrio gastroenteritis if harvested from contaminated waters, particularly the Gulf of Mexico. A northern latitude is not necessarily a barrier, as vibrio strains have been found in German coastal waters likely due to rising surface water temperatures fostering bacterial growth. The US Department of Agriculture’s (USDA) Food Safety and Inspection Service listed eggborne infection with Salmonella enteritidis as an important public health problem in the US in 2000. However, the problem appears to be ongoing, partly as a result of food-handling practices and specifically due to ingestion of products containing undercooked eggs, such as mayonnaise, ice cream, and custards. In addition, better food handling will not prevent infections passed in intact eggs. Postharvest methods to reduce Salmonella enteritidis human infection have been explored via refrigeration and physical (i.e., irradiation) or chemical (i.e., egg washing) methods; however, not all methods are accepted worldwide nor adequately studied for efficacy.
The USDA’s Animal Disease Research Unit has found that dairy farms are a potential source of Listeria monocytogenes, a zoonotic foodborne pathogen that is responsible for 28% of US food-related deaths every year. Other studies have found that dairy farms using antibiotics are also a reservoir for multidrug-resistant Salmonella typhimurium, E coli (O157:H7), and Yersinia enterocolitica, as well as other pathogenic organisms.
Produce may become contaminated with fecal pathogens during planting, irrigating, harvesting, processing, and shipping, or through contaminated water.
Food-service establishments can be a frequent source of foodborne infection, although the risk is also present in homes and any other setting that allows for poor temperature control in preparing, cooking, and storing food. A 2005 survey of food-service personnel found that more than 50% did not always wear gloves while touching ready-to-eat foods; almost 25% did not follow appropriate hand-washing guidelines; more than 33% did not always change gloves between handling raw meat and ready-to-eat foods; and more than 50% did not use a thermometer to check food temperatures. All these precautions should be used to eliminate risky practices in any setting where food is prepared, especially since those involved in food preparation are frequently asymptomatic carriers who may excrete the pathogen unknowingly.
The CDC, FDA, and USDA have established the Foodborne Diseases Active Surveillance Network (FoodNet) as a component of the CDC's Emerging Infections Program (EIP). FoodNet’s purpose is to monitor trends in foodborne diseases, determine the societal burden caused by these diseases, and assess which diseases are attributable to specific foods and settings in the US. Data listed on FoodNet’s website clearly indicate that the routine practice of using antibiotics in animal feed selects for the development of antimicrobial resistance. New methods include adding pre- and probiotics and other additives to animal feed to control bacterial contamination and gut homeostasis of animals. The site lists US farms and dairies in violation of guidelines to avoid antibiotic use. Tracing the origin of contaminated meat by FoodNet is complicated by the fact that a single hamburger might contain meat from many cows and the fact that the beef is handled at multiple facilities. These factors make it extremely difficult to identify the origin of contamination. Extensive research into flash gamma irradiation, also known as cold pasteurization, has shown effective eradication of bacterial contamination. However, low public acceptance has resulted in slow implementation of this process with food and animal feed. ,
What to Tell the Family
Complete avoidance of foodborne illness may not be possible. However, risk can be minimized through proper cooking and handling to avoid cross-contamination. Risk is further reduced by avoiding foods of animal origin. However, certain plant foods may also be contaminated during production, processing, or handling.
In the case of immunocompromised patients, ingestion of raw fish and raw meat is associated with a higher risk of foodborne illnesses. Patients with chronic diseases, especially liver disease, should be strongly encouraged to avoid raw shellfish, including oysters, clams, and shrimp.
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