COMMON TYPES OF FOOD POISONING|
SALMONELLOSIS (SALMONELLA) INFECTION
Salmonellosis, or Salmonella is one of the most common types of food poisoning. Between 2 and 4 million cases are treated every year in the United States. In 1885, pioneering American veterinary scientist, Daniel E. Salmon, discovered the first strain of Salmonella from the intestine of a pig. This strain was called Salmonella choleraesuis, the designation that is still used to describe the genus and species of this common human pathogen.
Salmonella is a type of bacteria that causes typhoid fever and many other infections of intestinal origin. Typhoid fever, rare in the U.S., is caused by a particular strain designated Salmonella typhi. But illness due to other Salmonella strains, just called "salmonellosis," is common in the U.S. Today, the number of known strains (technically termed "serotypes" or "serovars") of this bacteria total over 2300.
Salmonella serotypes typhimurium and enteritidis are the most common serotypes in the United States. In recent years, concerns have been raised because many strains of Salmonella have become resistant to several of the antibiotics traditionally used to treat it, in both animals and humans.
Salmonella bacteria are part of the natural intestinal flora of many animals. They are easily transmitted through the food supply, the hands of the food preparers, and the surfaces of objects such as knives and tabletops. Salmonella thrive in livestock that have been given antibiotics in their feed to make them grow faster and prevent disease in crowded and unsanitary conditions. At least one third of all chickens in the United States are infected with salmonella. Salmonellosis is typically associated with eggs. Salmonellosis is the leading cause of food poisoning death in America.
Salmonella infection symptoms can range from mild abdominal pain to severe diarrhea and dehydration to typhoid-like fever. The incubation period for salmonellosis (the time in between ingestion and the onset of the first symptom) may be from 6 hours to 10 days, but symptoms usually develop within 6 to 8 hours to 36 to 48 hours of eating contaminated foods. Diarrhea is often the first sign, often with fever and abdominal cramping. The onset may be sudden and there may be nausea and vomiting initially. The diarrhea often includes mucous and is occasionally bloody.
Infants, the elderly, immune suppressed persons and persons with sickle cell anemia are most susceptible to disease and suffer the most severe symptoms. It is in these individuals that the organism is most likely to gain access to the blood stream and possibly persist in sites of the body distant from the intestine, such as on the aorta or in the bone. Salmonella can also weaken the immune system and cause kidney and cardiovascular damage as well as arthritis.
External contamination from fecal matter, once a common source of salmonellosis, has almost been eliminated as a cause due to more stringent testing and inspection regimens implemented in the 1970s. The principal danger now comes from eggs because Salmonella enteritidis, the organism responsible for the majority of Salmonella infections, is now present in the ovaries of egg producing hens in the United States, and it contaminates the eggs before the shells form. Thus, eggs do not need to be cracked or unclean on the outside to be contaminated.
In 1985, an outbreak of Salmonella from contaminated milk occurred in five Midwestern states. As a result, 17,000 people became ill and 2 died. Eggs were once thought to be free of Salmonella. However, there has been a dramatic increase in the number of reported cases of food poisoning from foods containing raw or only partly cooked eggs, particularly in the Northeast. These foods include ice cream, eggnog, Caesar salad dressing, and Hollandaise sauce. Of 35 outbreaks of illness that were reported over a recent 2-year period and determined to be food poisoning, 24 were caused by contaminated eggs or foods containing these infected eggs. Certain strains of bacteria found in eggs are not destroyed if the eggs are poached or prepared over easy or
sunny-side up, in addition to other ways.
Salmonellosis as a result of the consumption of raw clams, oysters, and sushi made from raw fish has also been reported. Although this does not occur as often as Salmonella infection from eggs, meat, and poultry, it does happen.
Outbreaks of salmonellosis occur primarily in the warmer months. Most cases are the result of the consumption of contaminated foods, primarily chicken, eggs, beef, and pork products. People who eat raw or incompletely cooked meats are at greater risk of developing the disorder. Cooks who first handle raw meat or poultry and then handle other foods without washing their hands in between, endanger others; cooks who lick their hands or fingers after handling raw meat or poultry put themselves at risk of salmonella infection. People taking antibiotics are also at greater risk. Antibiotics can effectively treat bacterial infections, but, paradoxically, they can also promote infection by destroying good, competing bacteria and permitting the growth of bacteria that are antibiotic resistant. Another complication is the fact that a number of drugs that used to be useful in treating salmonellosis are no longer effective. This includes the drugs ceftriaxone (kefurox, Zinacef) and ciprofloxacin (Cipro). A Taiwanese strain of salmonella, called the "super salmonella" by some, is completely resistant to all known antimicrobials. People with AIDS are 20 times more likely to suffer from salmonellosis than other population groups.
RISK OF INFECTION
Salmonella is one of the most common enteric (intestinal) infections in the U.S. In some states (e.g. Georgia, Maryland) it is the most common, and overall it is the second most common food borne illness (usually slightly less frequent than Campylobacter infection.) The reported incidence of salmonellosis is about 17 cases per each 100,000 persons. Over 40,000 actual cases are reported yearly in the U.S. As only about 3-percent of Salmonella cases are officially reported nationwide, and many milder cases are never diagnosed, the true incidence is undoubtedly much higher. It is more common in the warmer months of the year. Approximately 500 to 1,000 persons die from Salmonella infections in the U.S. every year.
COMPLICATIONS OF INFECTION
Persons with diarrhea usually recover completely, although it may be several months before their bowel habits are entirely normal. A small number of persons who are infected with Salmonella will go on to develop pains in their joints, irritation of the eyes, and discomfort on urination. This is called Reiter's syndrome, or reactive arthritis, and starts a few weeks after the gastroenteritis. It can last for months or years, and can lead to chronic arthritis that may be difficult to treat. Antibiotic treatment does not make a difference in whether or not the person later develops Reiter's syndrome.
Salmonella septicemia (invasion of the blood stream) has been associated with the subsequent infection of virtually every organ system. In persons with atherosclerosis of the aorta it may grow there and persons with sickle cell disease or its variants tend to get infection in the bone (osteomyelitis) or joints (septic arthritis). Salmonella infection may persist in the gallbladder for months or years in rare individuals.
DIAGNOSIS OF SALMONELLOSIS
The diagnosis of salmonellosis is confirmed by cultures of stool or blood. In other words, specimens of blood or feces are placed in nutrient broth or on agar and incubated for 2 to 3 days. After that time, a trained microbiologist can recognize Salmonella bacteria if present by its unique characteristics. However, blood cultures are often not performed and in most cases the blood stream is not infected. In the stool, the laboratory is challenged to pick out Salmonella from many other similar bacteria that are normally present. In addition, many persons submit cultures after they have started antibiotics, which may make
it even more difficult for a microbiology lab to grow Salmonella. So, the diagnosis of salmonellosis may be problematic and many mild cases are culture negative.
In order to stop the increasing numbers of cases of Salmonella, consumers and producers must be educated on proper handling and cooking of eggs and other high-risk foods. Quick reporting and cooperation between all local, state and federal agencies are critical in identifying outbreaks, so fewer people are affected once food borne outbreaks occur.
- Cross-contamination of foods must be avoided. Uncooked eggs, poultry and meats should be kept separate from produce and ready-to-eat foods. Hands, cutting boards, counters, knives, and other utensils should be washed thoroughly after handling uncooked foods. It is recommended that bleach be used to wash cutting boards and counters used for food preparation immediately after use to avoid cross contaminating other foods.
- Hands should be washed before and after handling any food, and between handling different food items, after using the bathroom or changing a baby's diaper, and after contact with animals.
- Cook poultry, ground beef, and eggs thoroughly before eating. In order to insure that eggs do not contain viable Salmonella they must be cooked at least until the yoke is solid and meat and poultry must reach 160°F or greater throughout. This is important especially for for meats cooked in a microwave oven.
- Do not eat or drink foods containing raw eggs. Examples include homemade eggnog, Hollandaise sauce, and under cooked French toast. Note: There is more salmonella on the shell of the egg than in the egg itself. Some cooks drop an egg on a grill then pull the shell out, which is exactly the wrong thing to do!
- Never drink raw (unpasteurized) milk. Purchase only inspected eggs, animal food products and pasteurized milk.
- If you are served under cooked meat, poultry or eggs in a restaurant do not hesitate to send it back to the kitchen for further cooking.
- Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with foods of animal origin.
- Be particularly careful with foods prepared for infants, the elderly, and those with a compromised immune system.
- Wrap fresh meats in plastic bags at the market to prevent blood from dripping on other food items. Refrigerate foods promptly. Defrost meats in the refrigerator, minimize holding at room temperature.
- Make sure children, particularly those who handle pets, wash their hands properly.
- Wash hands with soap after handling reptiles, amphibians or birds, or after contact with pet feces. Infants and immunocompromised persons should have no direct or indirect contact with such pets.
About-Salmonella.com: Legal Information Regarding Food Poisoning Cases
Staphylococcus aureus is a spherical bacterium (coccus) which on microscopic examination appears in pairs, short chains, or bunched, grape-like clusters. These organisms are Gram-positive. Some strains are capable of producing a highly heat-stable protein toxin that causes illness in humans.
After Salmonella, Staphylococcus aureus is the second most frequent cause of food-borne illness. Staphylococci are responsible for approximately 25-percent of all cases of food poisoning. This microorganism is commonly found in the nose and throat, but if a food product becomes contaminated with it
(by being sneezed or coughed on, for example), the bacteria can grow and produce an enterotoxin, a toxin that specifically targets the cells of the intestines. It is this toxin, rather than the bacteria itself, that causes the food poisoning.
All people are believed to be susceptible to this type of bacterial intoxication, however, intensity of symptoms may vary.
Staphylococcus (staph) infection can manifest itself in a variety of ways, from food poisoning to skin infections to septicemia (blood infection). In severe cases it can be life threatening. Symptoms of staphylococci infection include diarrhea, nausea, vomiting, abdominal cramps, and prostration, usually beginning from 2 to 8 hours after consumption of the contaminated food. The onset of symptoms in staphylococcal food poisoning is usually rapid and in many cases acute, depending on individual susceptibility to the toxin, the amount of contaminated food eaten, the amount of toxin in the food ingested, and the general health of the victim. Some individuals may not always demonstrate all the symptoms associated with the illness. In more severe cases, headache, muscle cramping, and transient changes in blood pressure and pulse rate may occur. Recovery generally takes two days, However, it us not unusual for complete recovery to take three days and sometimes longer in severe cases.
Infective dose -- a toxin dose of less than 1.0 microgram in contaminated food will produce symptoms of staphylococcal intoxication. This toxin level is reached when S. aureus populations exceed 100,000 per gram.
RISK OF INFECTION
Foods that are frequently incriminated in staphylococcal food poisoning include meat and meat products; poultry and egg products; salads such as egg, tuna, chicken, potato, and macaroni; bakery products such as cream-filled pastries, cream pies, and chocolate eclairs; sandwich fillings; and milk and dairy products. Foods that require considerable handling during preparation and that are kept at slightly elevated temperatures after preparation are frequently involved in staphylococcal food poisoning.
Staphylococci exist in air, dust, sewage, water, milk, and food or on food equipment, environmental surfaces, humans, and animals. Humans and animals are the primary reservoirs. Staphylococci are present in the nasal passages and throats and on the hair and skin of 50-percent or more of healthy individuals. This incidence is even higher for those who associate with or who come in contact with sick individuals and hospital environments. Although food handlers are usually the main source of food contamination in food poisoning outbreaks, equipment and environmental surfaces can also be sources of contamination with S. aureus. Human intoxication is caused by ingesting enterotoxins produced in food by some strains of S. aureus, usually because the food has not been kept hot enough (60°C, 140°F, or above) or cold enough (72°C, 45°F, or below).
COMPLICATIONS OF STAPH INFECTION
Dehydration and muscle cramping from diarrhea and vomiting may occur with Staphylococcus aureus food poisoning. Fluid and electrolyte balance must be maintained when diarrhea and vomiting are present. Death from staphylococcal food poisoning is very rare, although such cases have occurred among the elderly, infants, and severely debilitated persons.
DIAGNOSIS OF STAPH
In the diagnosis of staphylococcal foodborne illness, proper interviews with the victims and gathering and analyzing epidemiologic data are essential. Incriminated foods should be collected and examined for staphylococci. The presence of relatively large numbers of enterotoxigenic staphylococci is good circumstantial evidence that the food contains toxin. The most conclusive test is the linking of an illness with a specific food or in cases where multiple vehicles exist, the detection of the toxin in the food sample(s). In cases where the food may have been treated to kill the staphylococci, as in pasteurization or heating, direct microscopic observation of the food may be an aid in the diagnosis. A number of serological methods for determining the enterotoxigenicity of S. aureus isolated from foods as well as methods for the separation and detection of toxins in foods have been developed and used successfully to aid in the diagnosis of the illness. Phage typing may also be useful when viable staphylococci can be isolated from the incriminated food, from victims, and from suspected carrier such as food handlers.
For detecting trace amounts of staphylococcal enterotoxin in foods incriminated in food poisoning, the toxin must be separated from food constituents and concentrated before identification by specific precipitation with antiserum (antienterotoxin) as follows. Two principles are used for the purpose: (1) the selective adsorption of the enterotoxin from an extract of the food onto ion exchange resins and (2) the use of physical and chemical procedures for the selective removal of food constituents from the extract, leaving the enterotoxin(s) in solution. The use of these techniques and concentration of the resulting products (as much as possible) has made it possible to detect small amounts of enterotoxin in food.
There are developed rapid methods based on monoclonal antibodies (e.g., ELISA, Reverse Passive Latex Agglutination), which are being evaluated for their efficacy in the detection of enterotoxins in food. These rapid methods can detect approximately 1.0 nanogram of toxin/gram of food.
Handwashing is the most important way to prevent infections from passing from person to person. Wash hands thoroughly before and after all food preparation. Any food service worker who has skin infections should not be handling food. Food preparation equipment must be thoroughly washed before it is used. Refrigerate meats and leftovers promptly. Keep hot foods hot (over 140°F) and cold foods cold (below 40°F).
The bacterium Clostridium botulinum, which commonly inhabits the soil in the form of harmless spores, can cause a particularly dangerous type of food poisoning. Of the various types of food poisoning, botulism is the among the most severe. It affects the central nervous system. As with Staphylococcus, it is not the bacteria but rather nerve toxins produced by C. botulinum that cause the poisoning and like staph, the bacteria can infect surface wounds. Wound-borne botulism is not common, but it can occur if an open sore becomes infected with the botulism bacteria. People who use intravenous drugs can also be infected by using dirty or shared needles. Infant botulism is a type of the disorder that usually affects children under 12 months of age. It can occur if a child ingests anything contaminated by botulism spores. This can include soil, cistern water, dust, and even some foods, such as raw honey.
These rod-shaped organisms grow best in low oxygen conditions. The bacteria form spores which allow them to survive in a dormant state until exposed to conditions that can support their growth. There are seven types of botulism toxin designated by the letters A through G; only types A, B, E and F cause botulism illness in humans. Types C and D are isolated to animals. Type G has been found in soil samples in Argentina, but no cases of illness involving type G have yet been reported.
The toxins produced by C. botulinum block the transmission of impulses from nerves to muscles, thus paralyzing the muscles. The paralysis often begins with the muscles that are responsible for eye movement, swallowing, and speech, and progresses to those in the torso and the extremities. Early symptoms of botulism include extreme weakness, double vision, droopy eyelids, slurred speech, dry mouth, and trouble swallowing. These symptoms typically appear 12 to 48 hours after the ingestion of the contaminated food, but they can occur as early as 6 hours or as late as 10 days. Eventually, muscle weakness affecting the entire body, including the muscles required for breathing, can result. Paralysis and death may occur in severe cases.
RISK OF INFECTION
In the United States an average of 110 cases of botulism are reported each year. Of these, approximately 25-percent are foodborne, 72-percent are infant botulism, and the rest are wound botulism. Even though the U.S. Centers for Disease Control (CDC) reported only 42 cases of botulism in the United States in 1994, it still remains a threat. Botulin toxin has been found in asparagus, beets, corn, stuffed eggplant, smoked and salted fish, green beans, ham, lobster, luncheon meats, mushrooms, peppers, sausage, soups, spinach, and tuna. Less common sources include chopped garlic in oil, tomatoes, baked potatoes that have been improperly handled and then kept in aluminum foil, and home-canned or fermented fish. Canned foods, especially those canned at home, are particularly prone to contamination with this potentially lethal organism. This is often due to improper canning techniques, usually the failure to use a pressure cooker to seal the jars adequately. A bulging lid or cracked jar can be a sign that the food within is contaminated, but botulism can occur even if a food container shows no sign of damage. Keeping food at room temperature for prolonged periods of time can also be a problem. In one reported case, a restaurant allowed a large batch of sauteed onions to be kept out throughout the day, instead of keeping them refrigerated, and small amounts were used as needed. Several people became very ill from botulin toxin in the onions.
Freezing, drying, and treatment with chemicals such as sodium nitrate prevent C. botulinum spores from growing and producing toxins. Although it does not kill the spores themselves, heating food to a temperature of at least 176°F for 30 minutes prevents food poisoning by destroying the lethal toxins.
COMPLICATIONS OF INFECTION
Botulism can result in death due to respiratory failure. However, in the past 50 years the proportion of patients with botulism who die has fallen from about 50-percent to 8-percent. A patient with severe botulism may require a breathing machine as well as intensive medical and nursing care for several months. Patients who survive an episode of botulism poisoning may have fatigue and shortness of breath for years and long-term therapy may be needed to aid recovery.
Health care providers may consider the diagnosis if the patient's history and physical examination suggest botulism. However, these clues are usually not enough to allow a diagnosis of botulism. Other diseases such as Guillain-Barre syndrome, stroke, and myasthenia gravis can appear similar to botulism, and special tests may be needed to exclude these other conditions. These tests may include a brain scan, spinal fluid examination, nerve conduction test (electromyography, or EMG), and a tensilon test for myasthenia gravis. The most direct way to confirm the diagnosis is to demonstrate the botulinum toxin in
the patient's serum or stool by injecting serum or stool into mice and looking for signs of botulism. The bacteria can also be isolated from the stool of persons with foodborne and infant botulism. These tests can be performed at some state health department laboratories and at CDC.
TREATMENT OF BOTULISM
The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a breathing machine (ventilator) for weeks, plus intensive medical and nursing care. After several weeks, the paralysis slowly improves. If diagnosed early, foodborne and wound botulism can be treated with an antitoxin which blocks the action of toxin circulating in the blood. This can prevent patients from worsening, but recovery still takes many weeks. Health care providers may try to remove contaminated food still in the gut by inducing vomiting or by using enemas. Wounds should be treated, usually surgically, to remove the source of the toxin-producing bacteria. Good supportive care in a hospital is the mainstay of therapy for all forms of botulism. Currently, antitoxin is not routinely given for treatment of infant botulism.
Botulism can be prevented. Foodborne botulism has often been from home-canned foods with low acid content, such as asparagus, green beans, beets and corn. However, outbreaks of botulism from more unusual sources such as chopped garlic in oil, chili peppers, tomatoes, improperly handled baked potatoes wrapped in aluminum foil, and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminum foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, persons who eat home-canned foods should consider boiling the food for 10 minutes before eating it to ensure safety. Instructions on safe home canning can be obtained from county extension services or from the US Department of Agriculture. Because honey can contain spores of Clostridium botulinum and this has been a source of infection for infants,
children less than 12 months old should not be fed honey. Honey is safe for persons 1 year of age and older. Wound botulism can be prevented by promptly seeking medical care for infected wounds and by not using injectable street drugs.
Public education about botulism prevention is an ongoing activity. Information about safe canning is widely available for consumers. State health departments and CDC have persons knowledgeable about botulism available to consult with health care providers 24 hours a day. If antitoxin is needed to treat a patient, it can be quickly delivered to a health care provider anywhere in the country. Suspected outbreaks of botulism are quickly investigated,
and if they involve a commercial product, the appropriate control measures are coordinated among public health and regulatory agencies. Health care providers should report suspected cases of botulism to a state health department.
A microorganism called Campylobacter jejuni, was not recognized as a cause of human foodborne illness prior to 1975. It has long been known to cause illness in cattle, has now been implicated in human illness as well. Many experts believe that the incidence of this infection is much higher than reported, because many people mistake it for a stomach virus. People tend not to associate their illness with food because it takes 3 to 5 days for these bacterial to produce symptoms.
Most cases Campylobacter infection occur as isolated, sporadic events, not as a part of the large outbreaks. Even though surveillance is very limited, over 10,000 cases are reported to the Centers for Disease Control and Prevention (CDC) each year. Active surveillance for cases indicates that over 17 cases for each 100,000 persons in the population (or about 46,000 cases) are diagnosed yearly. Undoubtedly, many more cases go undiagnosed and unreported. Campylobacteriosis occurs more frequently in the summer months than in the winter. Although Campylobacter does not commonly cause death, it has
been estimated that 100 persons with Campylobacter infections die each year from the infection.
Symptoms of C. jejuni food poisoning include abdominal cramps, diarrhea, fever, and possibly blood in the stool. Diarrhea is the most consistent and prominent manifestation of campylobacteriosis. It is often bloody. Typical symptoms of C. jejuni infection also include fever, nausea, vomiting, abdominal pain, headache, and muscle pain. A majority of cases are mild and do not require hospitalization and may be self-limited. However, C. jejuni infection can be severe and life threatening. Death is more common when other diseases (e.g., cancer, liver disease, and immuno-deficiency diseases) are present.
Children under the age of 5 and young adults aged 15 to 29 are the age groups most frequently affected. The incubation period (the time between exposure on onset of the first symptom) is typically 2 to 5 days, but onset may occur in as few as 2 days or as long as 10 days after ingestion. The illness usually lasts no more than one week; however, severe cases may persist for up to 3 weeks.
It can be present in the intestinal tracts of apparently healthy cattle, turkeys, chickens, sheep, dogs and cats, and can be contracted by eating or drinking food or water that has somehow become contaminated by the feces of an infected person or animal. Chickens, turkeys, and waterfowl are the most common carriers. It can be spread to all parts of the meat during the slaughtering process. Fortunately, heat destroys the bacteria, so it is possible to avoid this type of food poisoning by eating meat only if has been cooked thoroughly.
RISK OF INFECTION
Food is the most common vehicle for the spread of Campylobacter and poultry is the most common food implicated. Some case-control studies indicate that up to 70-percent of sporadic cases of campylobacteriosis are associated with eating chicken. Surveys by the USDA demonstrated that up to 88-percent of the broiler chicken carcasses in the USA are contaminated with Campylobacter while a recent Consumer Reports study identified Campylobacter in 63-percent
of more then 1000 chickens obtained in grocery stores. Other identified food vehicles include unpasteurized milk, under cooked meats, mushrooms, hamburger, cheese, pork, shellfish, and eggs.
Most cases of campylobacteriosis are sporadic or involve small family groups, although some common-source outbreaks involving many people have been traced to contaminated water or milk.
Other sources of Campylobacter, in addition to food water, that have been reported include children prior to toilet-training, especially in child care settings, and intimate contact with other infected individuals. C. jejuni is commonly present in the gastrointestinal tract of healthy cattle, pigs, chickens, turkeys, duck, and geese, and direct animal exposure can lead to infection. Pets that may carry Campylobacter include Birds, cats, dogs, hamsters, and turtles. The organism is also occasionally isolated from streams, lakes and ponds.
Campylobacter jejuni is a gram-negative, microaerophilic, thermophilic rod, growing best at 42°C and low oxygen concentrations. These characteristics are adaptations for growth in its normal habitat-the intestine of warm-blooded birds and mammals. Food, becomes contaminated from intestinal material during processing, but C. jejuni grows poorly on properly refrigerated foods. It does, however, survive refrigeration and will grow if contaminated foods are left out at room temperature. Campylobacter is sensitive to heat and other common disinfection procedures. Pasteurization of milk, adequate cooking of
meat and poultry, and chlorination or ozonation of water will destroy this organism. Several closely related species with similar characteristics, C. coli, C. fetus, and C. upsalienis, may also cause disease in humans.
SELECTED LISTINGS OF PRIOR CAMPYLOBACTER OUTBREAKS
||CASES / SOURCE
||200 / unknown
||30 / Unknown
||38 / Unknown
||87 / Unknown
||14 / Lettuce / Lasagna
||70 / Salad (suspected)
||82 / Tuna Salad
||17 / Chicken / Coleslaw / Potato Salad
||62 / Fruit Salad
||48 / Melon / Strawberries
||50 / Raw Milk
||34 / Pasta Salad / Au Gratin Potatoes
||23 / Milk
||20 / Cold Meat Tray
||10 / Chicken / Fruit
||42 / Raw Milk
||13 / Raw Milk
||23 / Raw Milk
||39 / Poultry
COMPLICATIONS OF INFECTION
Long-term consequences can sometimes result from a Campylobacter infection. Some people may develop a rare disease that affects the nerves of the body following campylobacteriosis. This disease is called Guillain-Barre syndrome. Although rare, it is the most common cause of acute generalized paralysis in the Western world. It begins several weeks after the diarrheal illness in a small minority of Campylobacter victims. It occurs when a person's immune system makes antibodies against components of Campylobacter and these antibodies attack components of the body's nerve cells because they are chemically similar to bacterial components.
Guillain-Barre syndrome begins in the feet and spreads up the body. Prickling sensations gives way to weakness that may lead to paralysis. It lasts for weeks to months and often requires intensive care. Full recovery is common, however victims may be left with severe neurological damage. Approximately 15 percent of Guillain-Barré victims remain bedridden or wheelchair bound at the end of one year.
Two therapies, intravenous immunoglobulin infusions and plasma exchange, may improve the rate of recovery in patients with Guillain-Barre syndrome.
It is estimated that approximately one in every 1000 reported campylobacteriosis cases leads Guillain-Barre syndrome. As many as 40 percent of Guillain-Barre syndrome cases in this country occur following campylobacteriosis. Miller Fisher Syndrome is another, related neurological syndrome that can follow campylobacteriosis and is also caused by immunologic mimicry. In Miller Fisher syndrome, the nerves of the head are affected more than the nerves of the body.
Another chronic condition that may be associated with Campylobacter infection is an arthritis called Reiter's syndrome. This is a reactive arthritis that most commonly affects large weight-bearing joints such as the knees and the lower back. It is a complication that is strongly associated with a particular genetic make-up; persons who have the human lymphocyte antigen B27 (HLA-B27) are most susceptible.
Campylobacter may also cause appendicitis or infect the abdominal cavity (peritonitis), the heart (carditis), the central nervous system (meningitis), the gallbladder (cholecystitis) the urinary tract, and the blood stream.
Many kinds of infections can cause diarrhea and the other symptoms associated with campylobacteriosis. Health care providers can look for bacterial causes of diarrhea by asking a laboratory to culture a sample of stool from an ill person. Microbiology laboratories now routinely perform culture procedures on stool specimens that are specifically designed to promote the growth and identification of Campylobacter jejuni and the other species of Campylobacter.
For treatment of Campylobacteriosis, patients with campylobacteriosis should drink plenty of fluids as long as the diarrhea lasts in order to maintain hydration. Antidiarrheal medications such as loperamide may allay some symptoms.
Campylobacter is usually causes a self-limited illness, but when it is identified, specific treatment with antibiotics is indicated, as treatment may shorten the course of the illness. In more severe cases of gastroenteritis, antibiotics are usually begun before culture results are known. Macrolide antibiotics (erythromycin, clarithromycin, or azithromycin) are the most effective agents for C. jejuni. Fluoroquinolone antibiotics (ciprofloxacin, levofloxacin, gatifloxacin, or moxifloxacin) can also be used, but resistance to this class has been rising, at least in part due to the use of this class of antimicrobial in poultry feed. In the U.S. these antibiotics are available only by prescription.
Infection control measures at all stages of food processing may help to decrease the incidence of Campylobacter infections, but the single most important and reliable step is to adequately cook all poultry products.
The most reliable method to ensure this is to use a cooking thermometer. A metal stem-type thermometer that is numerically scaled should be used to assure that food is cooked to the proper temperature. The thermometer should be accurate to plus (+) or minus (-) 2° Fahrenheit. Document that the thickest part of the chicken, turkey, duck or goose (the center of the breast) reaches 180°F or higher, as recommended by the U.S. Food and Drug Administration. The agency recommends at least 165°F for stuffing, 170°F for ground poultry products, and that thighs and wings be cooked until juices run clear.
Other control measures of import that are available to consumers and food service personnel include the following:
Choose the coolest part of the vehicle (generally the trunk in winter and cab in summer) to transport meat and poultry home from the market.
Defrost meat and poultry in the refrigerator. Place the item on a low shelf, on a wide pan, lined with paper towel; ensure that drippings do not land on foods below. If there is not enough time to defrost in the refrigerator, then use the microwave.
Do not cook stuffing actually inside the bird.
Rapidly cool leftovers.
Never leave food out at room temperature (either during preparation or after cooking) for more than 2 hours.
Avoid raw milk and products made from raw milk. Drink only pasteurized milk products.
Wash hands thoroughly using soap and water, concentrate on fingertips and nail creases, and dry completely with a disposable paper towel at the following times:
- After contact with pets, especially puppies, or farm animals.
- Before and after preparing food, especially poultry.
- After changing diapers or having contact with an individual with an intestinal infection.
- Children on arrival home from school or day-care.
Wash fruits and vegetables carefully, particularly if they are eaten raw. If possible, vegetables and fruits should be peeled.
HACCP.com: Food Safety - Food Poisoning Links
Another type of bacteria that can cause food poisoning is Clostridium perfringens, sometimes called the "food service germ". It is one of the most common causes of food borne illness. As early as 1895, Clostridium perfringens was associated with human diarrhea, although it was not until the 1940s that it was confirmed to be a cause of food poisoning.
Clostridium perfringens is an anaerobic, Gram-positive, sporeforming rod (anaerobic means unable to grow in the presence of free oxygen). It is widely distributed in the environment and frequently occurs in the intestines of humans and many domestic and feral animals. Spores of the organism persist in soil, sediments, and areas subject to human or animal fecal pollution.
This microorganism thrives in previously cooked food that is kept for a long period of time at room temperature. C. perfringens often survives heat well, so it is not affected by normal cooking. The bacteria multiply, forming spores and generating toxins that proliferate as foods cool and while they are stored. The toxins also are often heat-resistant. Meats, meat products, and gravy are the foods most frequently implicated and sources of the toxin. As foods cool, the bacteria multiply, forming spores and generating toxins.
Perfringens food poisoning is the term used to describe the common foodborne illness caused by C. perfringens. A more serious but rare illness is also caused by ingesting food contaminated with Type C strains. The latter illness is known as enteritis necroticans or pig-bel disease.
The symptoms of C. perfringens poisoning are usually limited to mild nausea and vomiting that last a day or less, but that can be a very serious problem for elderly people or people with Crohn's disease or HIV. The hallmark of Clostridium food poisoning is sudden, watery diarrhea accompanied by abdominal pain that can range from mild to severe. Usually there is no fever associated with this type of food poisoning. Contaminated meat and meat products are the most common sources of this type of food poisoning.
The common form of perfringens poisoning is characterized by intense abdominal cramps and diarrhea which begin 8 to 22 hours after consumption of foods containing large numbers of those C. perfringens bacteria capable of producing the food poisoning toxin. The illness is usually over within 24 hours but less severe symptoms may persist in some individuals, such as in the elderly or infirm, for 1 or 2 weeks. A few deaths have been reported as a result of dehydration and other complications but, are considered rare.
Necrotic enteritis (pig-bel) caused by C. perfringens is often fatal. Symptoms of this infection include abdominal pain, vomiting, bloody diarrhea and shock may occur. This disease also begins as a result of ingesting large numbers of the causative bacteria in contaminated foods. Deaths from necrotic enteritis (pig-bel syndrome) are caused by infection and necrosis of the intestines and from resulting septicemia. This disease is very rare in the U.S.
Infective Dose: The symptoms are caused by ingestion of large numbers (greater than 10 to the 8th) vegetative cells. Toxin production in the digestive tract (or in test tubes) is associated with sporulation. This disease is a food infection; only one episode has ever implied the possibility of intoxication (i.e., disease from preformed toxin).
RISK OF INFECTION
Clostridium bacteria are found in soil, in stool, and in the intestines of healthy people and of animals. Packages of uncooked meat or poultry frequently contain Clostridium. Clostridium can also be transferred into food from the hands of those preparing it. Proper handwashing is necessary since someone with dirty hands can introduce the bacteria into food where it will germinate and multiply.
Perfringens poisoning is one of the most commonly reported foodborne illnesses in the U.S. There were 1,162 cases in 1981, in 28 separate outbreaks. At least 10 TO 20 outbreaks have been reported annually in the U.S. for the past 2 decades. Typically, dozens or even hundreds of person are affected. It is probable that many outbreaks go unreported because the implicated foods or patient feces are not tested routinely for C. perfringens or its toxin. CDC estimates that about 10,000 actual cases occur annually in the U.S.
Institutional feeding (such as school cafeterias, hospitals, nursing homes, prisons, etc.) where large quantities of food are prepared several hours before serving is the most common circumstance in which perfringens poisoning occurs. The young and elderly are the most frequent victims of perfringens poisoning. Except in the case of pig-bel syndrome, complications are few in persons under 30 years of age. Elderly persons are more likely to experience prolonged or severe symptoms.
COMPLICATIONS OF INFECTION
Dehydration from diarrhea and vomiting may result. The young and elderly, or those with other illnesses may have more complications.
Clostridium perfringens food poisoning is suspected by the history and physical exam. A diagnosis might be confirmed with stool studies. Keep in mind that Clostridium are found in the stool of healthy people, so either large numbers (more than 1,000,000 organisms per gram of stool) or evidence of the toxin are needed.
Sometimes the diagnosis is made by finding Clostridium in the food. Standard bacteriological culturing procedures are used to detect the organism in
implicated foods and in feces of patients. Serological assays are used for detecting enterotoxin in the feces of patients and for testing the ability of strains to produce toxin. The procedures take 1-3 days.
Usually no treatment is needed, other than taking steps to prevent or treat dehydration. Antibiotics are not useful in Clostridium food poisoning.
Unlike many other types of bacteria that cause foodborne disease, clostridium perfringens is not completely destroyed by ordinary cooking. This is because it produces heat-resistant spores.
The bacteria are killed at cooking temperatures, but the heat-resistant spores they produce are able to survive and may actually be stimulated to germinate by the heat. If the food is not eaten at once but is allowed to cool slowly, the bacteria produced when the spores germinate multiply rapidly. Unless the food is reheated so that it is piping hot (at least to 140°F [60°C] and preferably to 167°F [75°C]), the bacteria will survive. After ingestion, if there are sufficient numbers present, the bacteria will produce toxins and the toxins will cause symptoms.
Foods most likely to be associated with clostridium perfringens food poisoning are those that are cooked slowly in large quantities and left to stand for a long time at room temperature.
Clostridium grows best between 45°F and 140°F. Prepared foods should be kept cooler or warmer than this.
Wash hands before preparing or serving foods. When handling raw meat or poultry, consider them contaminated! Wash your hands and any surfaces they have touched before proceeding. Be sure that meat, poultry, and fish dishes are fully cooked and do not interrupt cooking to finish it later.
Do not leave prepared foods unrefrigerated for more than two hours. When foods are taken from warming tables, they should be refrigerated immediately, not left at room temperature to cool.
Prepared foods should be reheated to at least 165°F before serving.
Not all food-borne illness is the result of bacterial contamination and infection. Giardia lamblia is a protozoan that infects the small intestine. It is a single celled parasitic animal (microorganism) that moves with the aid of five flagella. In Europe, it is sometimes referred to as Lamblia intestinalis. It lives in the intestines of humans and some wild and domestic animals. Organisms that appear identical to those that cause human illness have been isolated from domestic animals (dogs and cats) and wild animals (beavers and bears). A related but morphologically distinct organism infects rodents, although rodents may be infected with human isolates in the laboratory. Giardiasis is associated with the consumption of contaminated water. It can also be transmitted to raw foods that have grown in contaminated water. Cool, moist environments are conducive to the growth of this microorganism. It is the most frequent cause of non-bacterial diarrhea in North America.
Symptoms generally occur within 1 to 3 weeks of infection and include chronic diarrhea with frequent loose and pale greasy stools, constipation, abdominal cramps and pain, flatulence, bloating, loss of appetite and weight loss, fatigue, nausea, and vomiting. Asymptomatic infection (i.e. where persons are infected, carry and excrete but do not develop any symptoms) is common with Giardia lamblia, and for this reason it is recommended that all household
members are tested where one is known to be infected.
The incubation period (i.e. the time between ingestion of the Giardia lamblia cysts and onset of illness) can be anywhere from 3 to 25 days or longer but the average period is 7 to 10 days.
CAUSE & RISK OF INFECTION
Food contaminated by an infected food handler, either after cooking or food to be eaten without cooking. Poor personal hygiene can result in the infection being passed from person to person, especially in children. In this and other westernized countries water is rarely contaminated by human or animal excreta. In less developed countries contaminated water is more common and can only be made safe by boiling or filtration. Chlorination and water purifying tablets are not effective.
COMPLICATIONS OF INFECTION
If the symptoms are severe and/or prolonged, seek medical advice. It is particularly important that young children and the elderly, and those already under medical supervision are treated.
Giardiasis is more prevalent in children than in adults, possibly because many individuals seem to have a lasting immunity after infection. This organism is implicated in 25-percent of the cases of gastrointestinal disease and may be present asymptomatically. The overall incidence of infection in the United States is estimated at 2-percent of the population. This disease afflicts many homosexual men, both HIV-positive and HIV-negative individuals. This is presumed to be due to sexual transmission. The disease is also common in child day care centers, especially those in which diapering is done.
About 40-percent of those who are diagnosed with giardiasis demonstrate disaccharide intolerance during detectable infection and up to 6 months after the infection can no longer be detected. Lactose (i.e., milk sugar) intolerance is most frequently observed. Some individuals (less than 4%) remain symptomatic more than 2 weeks; chronic infections lead to a malabsorption syndrome and severe weight loss. Chronic cases of giardiasis in immunodeficient and normal individuals are frequently refractile to drug treatment. Flagyl is normally quite effective in terminating infections. In some immune deficient individuals, giardiasis may contribute to a shortening of the life span.
Normally illness lasts for 1 to 2 weeks, but there are cases of chronic infections lasting months to years. Chronic cases, both those with defined immune deficiencies and those without, are difficult to treat. Giardiasis occurs throughout the population, although the prevalence is higher in children than adults. Chronic symptomatic giardiasis is more common in adults than children.
The disease mechanism is unknown, with some investigators reporting that the organism produces a toxin while others are unable to confirm its existence. The organism has been demonstrated inside host cells in the duodenum, but most investigators think this is such an infrequent occurrence that it is not responsible for disease symptoms. Mechanical obstruction of the absorptive surface of the intestine has been proposed as a possible pathogenic mechanism, as has a synergistic relationship with some of the intestinal flora.
Giardia can be excysted, cultured and encysted in vitro; new isolates have bacterial, fungal, and viral symbionts. Classically the disease was diagnosed by demonstration of the organism in stained fecal smears.
Several strains of G. lamblia have been isolated and described through analysis of their proteins and DNA; type of strain, however, is not consistently associated with disease severity. Different individuals show various degrees of symptoms when infected with the same strain, and the symptoms of an individual may vary during the course of the disease.
Infectious Dose: Ingestion of one or more cysts may cause disease, as contrasted to most bacterial illnesses where hundreds to thousands of organisms must be consumed to produce illness.
Giardia lamblia is frequently diagnosed by visualizing the organism, either the trophozoite (active reproducing form) or the cyst (the resting stage that is resistant to adverse environmental conditions) in stained preparations or unstained wet mounts with the aid of a microscope. A commercial fluorescent antibody kit is available to stain the organism. Organisms may be concentrated by sedimentation or flotation; however, these procedures reduce the number of recognizable organisms in the sample. An enzyme linked immunosorbant assay (ELISA) that detects excretory secretory products of the organism is also available. So far, the increased sensitivity of indirect serological detection has not been consistently demonstrated.
Food is analyzed by thorough surface cleaning of the suspected food and sedimentation of the organisms from the cleaning water. Feeding to specific pathogen-free animals has been used to detect the organism in large outbreaks associated with municipal water systems. The precise sensitivity of these methods has not been determined, so that negative results are questionable. Seven days may be required to detect an experimental infection.
Always wash your hands after using the toilet and before preparing, handling or eating food.
Do not drink water from rivers, streams, etc. If you have to drink water from outside sources, you should boil it first. Endeavor not to swallow water accidentally when swimming or taking part in other water sports on fresh water lakes, reservoirs, rivers, etc.
When abroad in under-developed countries do not drink tap water unless it has been boiled for at least a minute or properly filtered. Water purifying tablets will not kill the cysts. Be careful with uncooked or cold foods, ice, salads and unwashed fruit.
Increase household hygiene precautions if anyone has diarrhea.
Ensure that children, especially in close communities, such as playgroups or nursery schools, are properly toilet trained and that hand washing is supervised. Children with diarrhea should not attend playgroups or nursery.
Giardia lamblia can easily be passed from one person to another if there is a breakdown in personal hygiene. If someone in your household has Giardia lamblia, follow these precautions when taking care of an infected individual:
Prevention of food poisoning is the aim and good personal hygiene, hygienic kitchen practices, proper storage of food items in the fridge, and thorough cooking will help protect you and your family from infection.
- Where possible use rubber or disposable gloves when cleaning up. Wash hands after contact with an infected person.
- Soiled clothing or bedding should be washed on the hot cycle of your washing machine.
- Clean surfaces and rubber gloves with hot water and disinfectant, and wash your hands thoroughly.
- When the toilet is flushed the lid should be down to prevent water droplets settling on surfaces in the room. After flushing always wash your hands and clean surfaces and handles frequently using a suitable disinfectant. Clean and disinfect the toilet, the toilet handle, water faucets and door handles regularly with a disinfectant.
- Shared towels can spread the cysts from one person to another. The person with Giardia lamblia should be allocated separate face wash cloths and towels that should not be used by anyone else.
- Young children should not be bathed together or share the same bath water as the water temperature will not be sufficient to destroy the cysts.
- Ideally the infected person should not prepare food. If this is not possible, then hands should be washed thoroughly, nails scrubbed and prepare only food that will be thoroughly cooked afterwards. Dishes should be washed in hot soapy water and preferably not by the infected person.
- Food handlers in commercial food premises must not under any circumstances work while they have symptoms of a gastrointestinal illness (vomiting or diarrhea). Food handlers who have been free of symptoms for at least 48 hours and are not taking any anti-diarrheal medicines (this does not include antibiotics) may return to work providing they are meticulous with regard to their personal hygiene. It is important for food handlers to inform their employer of their illness as some employers insist that food handlers are able to submit a negative stool specimen prior to their return to work. If you visit your health care provider, remember to say that you are a food handler if this applies to your situation.
CDC: Giardiasis Infection Fact Sheet
OutdoorPlaces.com: Giardia lamblia - Don't Get Beaver Fever
Trichinella spiralis is a roundworm that causes the infection known as trichinosis. Trichinosis is caused by the colonization of trichinella larvae in muscles where they grow an encyst. It is most often the result of eating raw or improperly cooked or processed pork or pork products and bear meat.
The worm was first reported in man in 1835 and was first recorded in the United States in 1846. It was demonstrated that Trichinella caused serious disease in man in 1865. This nematode was first discovered by a medical student in London who noted during dissection of a cadaver that muscle tissue contained gritty particles which tended to dull a scalpel.
The worm was at one time widely distributed in Europe and the United States. It is thought to have originated in the northern hemisphere, but now is known from some areas in South America and Africa. It occurs in New Zealand but not in Australia.
First symptoms of infection include nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort and are due to invasion by adult worms. Migrating juveniles cause pain as they invade muscles tissue and the larvae cause a severe host reaction that results in soreness and tenderness of the muscles. Headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, diarrhea, or constipation follow the first symptoms. There may
also be edema (swelling), delirium, cardiac and pulmonary difficulty (heart and breathing problems), pneumonia, nervous disorders, deafness and delayed or lost reflexes if infection is heavy. Severe symptoms are likely if the levels exceed 100 larvae per gram of muscle (8,400 per 3 ounces of muscle tissue). Although this parasite probably only rarely causes fatalities in humans, it can cause extreme discomfort.
Abdominal symptoms can occur 1 to 2 days after infection. Further symptoms usually start 2 to 8 weeks after eating contaminated meat. Symptoms may range from very mild to severe and relate to the number of infectious worms consumed in meat. Often, mild cases of trichinellosis are never specifically diagnosed and are assumed to be the flu or other common illnesses.
Trichinella spiralis is a parasitic roundworm. The life cycle of the parasite begins when the infectious cysts are eaten with the flesh of any meat eating animal. The cysts are digested by the acid in the stomach, dissolving the hard covering of the cyst, releasing the worms. The worms pass into the small intestine and, in 1 to 2 days, become mature. After mating, adult females lay eggs. The female hatches the immature worms (larvae) that are carried by the blood and travel through the arteries and lymph to the muscles. Within the muscles, the worms curl into a ball and encyst (become enclosed in a capsule). Infection occurs when these encysted worms are consumed in meat.
THE TRICHELLA LIFE CYCLE
This nematode has no stages outside a host. The adult worms are found attached to or buried in the mucosa of the duodenum. After mating the males die. Females (ovoviviparous) produce living young (approximately 1,500 per female over a period of 4 to 16 weeks) and then die. Juveniles enter the lymphatics and mesenteric veins and are found throughout the arterial circulation between the 7th and 25th day after infection. They travel in the hepatoportal system through the liver, then to the heart, lungs, and the arterial system, which distributes them throughout the body. They are transported to striated muscles, penetrate individual fibers, and cysts are formed around the juveniles. Within cysts, juveniles remain viable for many years, up to 25 years in man and 11 years in pigs. There is agreement that there are four juvenile stages but disagreement in the literature as to whether or not nematode development occurs within the cyst. When viable encysted juveniles are ingested, they are digested from the cysts and pass to the duodenum where they mature. Humans are essentially a dead end for the parasites.
Characteristics: The males measure 1.4 to 1.6 mm long and are more slender at the anterior than the posterior end. The anus is nearly terminal and has a large papilla on each side of it. A copulatory spicule is absent. Stichocytes are arranged in a row following a short muscular esophagus. Females are about twice the size of males, also tapering toward the anterior end. The anus is nearly terminal. The vulva is located near the middle of the esophagus, which is about a third the length of the body. The single uterus is filled with developing eggs in its posterior portion, whereas the anterior portion contains fully developed, hatching juveniles.
CAUSE & RISK OF INFECTION
Trichinosis is probably best known as a parasite that humans contract from eating raw or under cooked pork. If you eat raw or under cooked meats, particularly pork, bear, wild feline (such as a cougar), fox, dog, wolf, horse, seal, wild boar, or walrus, you are at risk for trichinosis. Through an aggressive program of meat inspection, the incidence of trichinosis in pigs in the United States has been lowered to less than 1 percent, so it is unlikely (but not impossible) that pork products purchased in your local supermarket will contain Trichinella larvae. Most recent outbreaks of trichinosis in the United
States have been traced to pork products from pigs that have not been inspected and that have been slaughtered privately. Because of its low host-specificity, almost any "wild" meat should be considered suspect, and hunters should be careful when preparing meat from their kills. In particular, a number of infections have been traced to contaminated bear meat.
Infection can only occur by eating raw or under cooked meat containing Trichinella worms so you cannot spread it to others.
COMPLICATIONS OF INFECTION
In severe cases, death can occur. For mild to moderate infections, most symptoms subside within a few months. Fatigue, weakness, and diarrhea may last for months.
DIAGNOSIS & TREATMENT
If you think you or other family member might have trichinellosis, see your health care provider. Your health care provider can order tests and treat symptoms of trichinellosis infection. If you have eaten raw or under cooked meat, you should tell your health care provider.
Many cases are never diagnosed because of the vagueness of the symptoms. Muscle biopsy can be conducted and involves pressing muscle tissue between glass plates to look for cysts. Xenodiagnosis involves feeding suspected muscle to laboratory rats. A blood test can show if you have trichinellosis.
There is no cure for this infection. Relieve of symptoms are usually done with analgesics and corticosteroids. Check with your health care provider about safe and effective prescription drugs that may be available to treat Trichinellosis. Treatment should begin as soon as possible and the decision to treat is based upon symptoms, exposure to raw or under cooked meat, and laboratory test results.
Infection was once very common; however, infection is now relatively rare. From 1991 to 1996, an annual average of 38 cases per year were reported. The number of cases has decreased because of legislation prohibiting the feeding of raw meat garbage to hogs, commercial and home freezing of pork, and the public awareness of the danger of eating raw or under cooked pork products. Cases are less commonly associated with pork products and more often associated with eating raw or under cooked wild game meats.
Although there have been marked reductions in the percentage of hogs carrying encysted juveniles in the United States, there is considerable variation from one part of the United States to another. It is therefore a wise precaution to avoid uncooked pork products. In the United States Trichinella occurred in 0.4 to 2.5-percent of the prepared pork products examined in some areas (1961); however some areas had as much as 10-percent infection. In Chile 0.22-percent of 500,000 hogs were infected (1964). In Germany only 0.00026-percent of 14,000,000 hogs were infected (1965). It has been estimated that 3/4 of the persons
infected with Trichinella are from North America.
- Thoroughly cook pork (at least 160°F) and other potential infected meats (bear, walrus, wild pigs, etc).
- Cook garbage fed to hogs and avoid cross-contamination of beef with pork. The concern from trichinosis is not as great today with improved pork production practices.
- Proper meat handling, ordinary curing and salting of pork products will not kill encysted juveniles.
- Freezing is effective if carried out properly. The freezing requirements differ with the size of the meat. Pieces not exceeding 6 inches in thickness require 20 days at 5°F, 10 days at -10°F, 6 days at -20°F. Larger pieces require longer periods. Quick freezing and storage for 2 days is effective.
Trichinella.org: Trichinella Biological Page
Scomboid poisoning (also called histamine poisoning) is a relatively rare type of food poisoning that can occur after the consumption of foods that contain high levels of histamine and possibly other vasoconstrictive amines and compounds. Histamine and other amines are formed by the growth of certain bacteria and the subsequent action of their decarboxylase enzymes on histidine and other amino acids in food, either during the production of a product such as Swiss cheese or by spoilage of foods such as fishery products, particularly tuna or mahi mahi and mackerel. After the fish is caught, decomposition by bacteria in the fish can trigger the production of high levels of a chemical called histamine.
When the fish is eaten, initial symptoms may include a tingling or burning sensation in the mouth and throat, a rash (hives) on the upper body, sweating, dizziness, and a drop in blood pressure. In a matter of minutes the histamine can cause symptoms to progress to include facial flushing, nausea, vomiting,
abdominal pain, and/or diarrhea. Frequently headaches and itching of the skin are encountered. Severe cases may blur vision and cause respiratory distress and swelling of the tongue. Hospitalization may be required, particularly in the case of elderly or people with allergies that may be very sensitive to a histamine reaction, and impaired patients. Fortunately, symptoms usually last for approximately 4 to 6 hours and subside in 24 hours, rarely exceeding one to two days.
CAUSE & RISK OF INFECTION
Fishery products that have been implicated in scombroid poisoning include the tunas (e.g., skipjack and yellowfin), mahi mahi, bluefish, sardines, mackerel, amberjack, and abalone. Many other products also have caused the toxic effects. The primary cheese involved in intoxications has been Swiss cheese. The toxin forms in a food when certain bacteria are present and time and temperature permit their growth. Distribution of the toxin within an individual fish fillet or between cans in a case lot can be uneven, with some sections of a product causing illnesses and others not. Neither cooking, canning, or freezing reduces the toxic effect. Common sensory examination by the consumer cannot ensure the absence or presence of the toxin. Chemical testing is the only reliable test for evaluation of a product.
Scombroid poisoning remains one of the most common forms of fish poisoning in the United States. Even so, incidents of poisoning often go unreported because of the lack of required reporting, a lack of information by some medical personnel, and confusion with the symptoms of other illnesses. Difficulties with underreporting are a worldwide problem. In the United States from 1968 to 1980, 103 incidents of intoxication involving 827 people were reported.
For the same period in Japan, where the quality of fish is a national priority, 42 incidents involving 4,122 people were recorded. Since 1978, 2 actions by FDA have reduced the frequency of intoxications caused by specific products. A defect action level for histamine in canned tuna resulted in increased industry quality control. Secondly, blacklisting of mahi mahi reduced the level of fish imported to the United States.
All humans are susceptible to scombroid poisoning; however, the symptoms can be severe for the elderly and for those taking medications such as isoniazid. Because of the worldwide network for harvesting, processing, and distributing fishery products, the impact of the problem is not limited to specific geographical areas of the United States or consumption pattern. These foods are sold for use in homes, schools, hospitals, and restaurants as fresh, frozen, or processed products.
COMPLICATIONS OF INFECTION
The onset of intoxication symptoms is rapid, ranging from immediate to 30 minutes. The duration of the illness is usually 3 hours, but may last several days.
DIAGNOSIS & TREATMENT
Diagnosis of the illness is usually based on the patient's symptoms, time of onset, and the effect of treatment with antihistamine medication. The suspected food must be analyzed within a few hours for elevated levels of histamine to confirm a diagnosis. The suspected food must be analyzed within a few hours for elevated levels of histamine to confirm a diagnosis.
An official method was developed at FDA to determine histamine, using a simple alcoholic extraction and quantitation by fluorescence spectroscopy. There are other untested procedures in the literature.
Confirmation for scombroid poisoning is a simple histamine analysis of the suspect fish. A common, routine fluorometric procedure can determine milligrams (mg) of histamine per 100 grams (g) of edible fish. Histamine concentrations near or above 100 mg / 100 g are typically noted in actual illnesses. Regulatory guidelines have not been established for all the various fishes of concern, but 50 mg / 100 g is inferred from the U.S. FDA's poisonous action level for tuna.
Symptoms for scombroid poisoning can be easily confused with an allergy or other form of food poisoning, and vice versa. For example, some symptoms for scombroid poisoning are similar to ciguatera, another form of marine fish poisoning. Distinguishing these illnesses can be complicated, particularly about warm water regions.
What should one do if they suspect scombroid poisoning?
- Consult a health care provider, explaining your concerns, types and amount of food eaten, and when the symptoms began.
- Try to obtain portions of the meal, particularly the suspect fish. These portions must be carefully handled, packaged and frozen to prevent any deterioration.
- Try to verify the species and size of suspect fish, and how it was cooked and handled prior to cooking. Inquire where the fish came from. Knowledge of species, source and prior handling could implicate other forms of food poisoning. Note the method or source used to verify the species, realizing local vernaculars and menu nomenclature can be misleading.
- Consult with other professionals in public health, food safety regulation or academic research that can better advise your health care provider. Many health care providers are not familiar with scombroid poisoning.
Avoid foods that may produce scombroid poisoning if you have severe histamine reactions.
Scombroid poisoning cannot be detected by appearance or taste. Proper handling of fish is the best safeguard. Studies have demonstrated that toxic histamine levels can be generated within less than six to 12 hours exposure without ice or refrigeration.
Remember potential scombrotoxic fish belong to a particular group of species that have been allowed to initially spoil. These species should always receive special care in handling, washing, and proper icing, refrigeration or immediate freezing to prevent bacterial growth and spoilage. Studies have demonstrated toxic histamine levels can be generated within less than 6 to 12 hours exposure without ice or refrigeration. This problem is of particular concern immediately after catch aboard a commercial or recreational boat. Likewise, the recreational catch lying on a warm dock or beach is prone to histamine production in certain species. The adverse consequence is not severe, but discomforting and alarming enough to warrant a little extra care. Prevention is simple and preferable to treatment which is similar as used for allergic reactions. Common advice from health care providers includes treatments with antihistamines.
ESCHERICHIA COLI (E-Coli 0157)
Escherichia coli is a common organism naturally found in the intestinal tract of man and some animals, where it actually serves a useful function. It helps to suppress harmful bacteria and aid in the absorption of vitamins. But sometimes, under the right circumstances, E. coli can cause serious illness. The
reason for the change from benign or friendly to pathogenic is not known. But this can be a very serious illness, particularly for the very young, the elderly, and those with compromised immune systems. This bacteria is found in meat, vegetables, and some unpasteurized juices or fruits.
E. coli, like some other potential pathogens, is also readily found in damp, ambient temperature environments e.g. soil, vegetation, moist or wet areas in factories, untreated water etc. There are many types and strains of E. coli, a few of which are potentially pathogenic. Different strains may cause illness by different infective and toxin-producing mechanisms.
Symptoms vary according to the strain of E.coli encountered, and the resistance of the individual to such illnesses. Infants, young children, elderly and sick people are generally more susceptible to E.coli (and other) infections than healthy older children and adults. Children are more likely than adults to have symptoms.
More than 700 serotypes of E. coli have been identified. The different serotypes are distinguished by their "O" and "H" antigens on their bodies and flagella. The E. coli serotypes that are responsible for the numerous cases of contaminated foods and beverages are those that produce Shiga toxin (Stx), so called because the toxin is virtually identical to that produced by another bacteria known as Shigella Desenteria Type 1 (that also has symptoms of bloody diarrhea and hemolytic uremic syndrome [HUS]. The best known and most notorious Stx-producing strain of E. coli is known as E. coli 0157:H7. This strain of E. coli bacteria can cause illness ranging from mild diarrhea to severe inflammation of the large intestine. Shiga toxin is listed as a potential bioterrorist bacteria by the CDC because it is one of the most potent toxins known to humans. It is a possibility that the DNA from Shiga toxin-producing Shigella bacteria was transferred by a virus that infects bacteria (bacteriophage) to otherwise harmless E. Coli bacteria, resulting in a bacteria with the genetic material for producing Shiga toxin. Although E. coli 0157:H7 is responsible for the majority of illnesses attributed to E. coli in humans, there are additional Stx-producing E. coli strains, such as E. coli 0.121:H19, that also cause hemorrhagic colitis, and post-diarrheal hemolytic uremic syndrome (D+HUS). HUS is a syndrome that is defined by hemolytic anemia (red blood cell destruction), thrombocytopenia (low platelet count), and acute kidney failure.
Diarrhea is the most common symptom; this can be mild and settle within two weeks but it can sometimes be more severe with nausea and vomiting, abdominal pain (stomach cramping) and bloody diarrhea. Some people can be infected but may not show any symptoms. A very small number of cases may develop what is called hemolytic uremic syndrome (HUS), which is a form of acute kidney failure. HUS is a more likely complication in children and the elderly and requires admission to hospital for treatment.
Most people get better in about a week. They often do not see a health care provider and do not know that E. coli caused their illness.
The bacteria are found in the gastrointestinal tract of some cattle and other domesticated animals. Transmission to humans usually occurs through eating contaminated foodstuffs particularly beef products. Outbreaks have been associated with under cooked beef burgers and mince, lamb, pork, chicken and turkey, and unpasteurized milk, contaminated water and vegetables. Infection can also follow contact with infected animals, particularly on farms and animal sanctuaries.
E. coli infection can occur by coming into contact with the feces, or stool, of humans or animals. This can happen when you drink water or eat food that has been contaminated by feces. Stx-producing E. coli have several characteristics that make them dangerous to humans. The bacteria are hardy and can survive several weeks on surfaces, such as counter tops, and up to a year in some materials such as compost. They have a very low infectious dose, meaning it does not take many bacteria (less than 50) to cause an infection in the host's intestinal tract.
E. Coli in Food: E. coli can get into meat during processing. If the infected meat is not cooked to 160°F, the bacteria can survive and infect a person eats the meat. This is the most common way people in the United States become infected with E. coli. Any food that has been in contact with raw meat can also become infected.
Other foods that can be infected with E. coli include:
E. coli in Water: Human or animal feces infected with E. coli sometimes get into lakes, pools, and water supplies. People can become infected when a contaminated city or town water supply has not been properly treated with chlorine or when people accidentally swallow contaminated water while swimming in a lake, pool, or irrigation canal.
- Raw milk or dairy products. Bacteria can spread from a cow's udders to its milk. Check the labels on dairy products to make sure they contain the word "pasteurized." This means the food has been heated to destroy bacteria.
- Raw fruits and vegetables, such as lettuce, alfalfa sprouts, or unpasteurized apple cider or other unpasteurized juices that have come in contact with infected animal feces.
E. coli from Person-To-Person Contact: The bacteria can also spread from one person to another, usually when an infected person does not wash his or her hands well after a bowel movement. E. coli can spread from an infected person's hands to other people or to objects.
The length of time from ingestion of the organism until the start of the symptoms is usually between 1 and 6 days but may be as long as 14 days.
Minimizing the risk of infection:
- Wash your hands before preparing food and after handling raw meat.
- Regularly clean and disinfect kitchen surfaces, equipment and utensils.
- Ensure that meat is defrosted thoroughly before being properly cooked - follow the manufacturer's cooking instructions. This particularly applies to minced beef.
- Keep cooked meat separate from raw meat at all times.
- Thoroughly rinse salads, fruit and vegetables in clean, running water.
- Keep raw meat separate from all other foods, especially desserts, cooked meats and salads, which do not need cooking.
E. coli can cause serious problems with the blood or kidneys, with symptoms of pale skin, fever, weakness, bruising, and passing only small amounts of urine. People with E. Coli infection with serious problems involving the blood and kidneys may need blood transfusions or dialysis. Dialysis is a treatment that helps filter waste products from the blood when the kidneys are not working correctly.
DIAGNOSIS & TREATMENT
A health care provider may suspect E. coli infection after questions and an examination. Diagnosis is done by obtaining and testing a stool sample for E. coli.
If you have E.coli symptoms:
The Centers for Disease Control and Prevention (CDC) estimates that every year at least 2000 Americans are hospitalized, and about 60 die as a direct result of E. coli infections and its complications. A recent study estimated the annual cost of E. coli O157:H7 illnesses to be $405 million (in 2003 dollars) which included $370 million for premature deaths, $30 million for medical care, and $5 million for lost productivity.
- If the symptoms are severe and/or prolonged, seek medical advice. It is particularly important that young children and the elderly, and those already under medical supervision are treated.
- If a member of the household is suffering from vomiting and diarrhea, the infection could be passed on to others. The main treatment is rest and fluids. Keeping your body hydrated is important since diarrhea causes the body to lose more water than usual, leading to dehydration. Dehydration is especially dangerous for babies and older adults. Taking frequent small sips of water throughout the day will help prevent dehydration.
- Do not take diarrhea medication. It can slow down the digestion process, allowing your body to absorb more of the E. coli toxins over time. Call your health care provider instead.
- Clean and disinfect the toilet, toilet flush, taps and door handle regularly with a disinfectant.
- Make sure you wash your hands after contact with an infected person.
- If you work as a food handler, make sure that you tell your employer and the health care provider.
E. coli O157:H7 was first recognized as a foodborne pathogen in 1982 during an investigation into an outbreak of hemorrhagic colitis (bloody diarrhea) associated with consumption of contaminated hamburgers. The following year, Shiga toxin (Stx), produced by the then little-known E. coli O157:H7, was identified as the real culprit. In the ten years following the 1982 outbreak, approximately thirty E. coli O157:H7 outbreaks were recorded in the United States. The actual number that occurred is probably much higher because E. coli O157:H7 infections did not become a reportable disease (required to be reported to public health authorities) until 1987. As a result, only the most geographically concentrated outbreaks would have garnered enough attention to prompt further investigation. It is important to note that only about 10-percent of infections occur in outbreaks, the rest are sporadic. The CDC has estimated that 85-percent of E. coli O157:H7 infections are foodborne in origin. In fact, consumption of any food or beverage that becomes contaminated by animal
(especially cattle) manure can result in contracting the disease. Foods that have been sources of contamination include ground beef, venison, sausages, dried (non-cooked) salami, unpasteurized milk and cheese, unpasteurized apple juice and cider, orange juice, alfalfa and radish sprouts, lettuce, spinach,
WebMD: E.Coli Infection
Ecoil.com: About E. Coli Food Poisoning
HEPATITIS A & HEPATITIS E
Hepatitis is a general term meaning inflammation of the liver. Hepatitis is a disease that can be caused by a variety of different viruses such as hepatitis A, B, C, D and E. Since the development of jaundice is a characteristic feature of liver disease, a correct diagnosis can only be made by testing patients' sera for the presence of specific viral antigens and/or anti-viral antibodies. Hepatitis A and E viruses can be transmitted by direct contact with fecal matter or with foods contaminated by fecal matter. They can also be transmitted by contaminated water.
HEPATITIS A (HAV)
Hepatitis A is a viral Disease which affects the liver. It occurs most often in school children and young adults.
The illness usually begins with a sudden onset of fever (temperature), feeling unwell, loss of appetite, nausea and stomach pain. This is followed within a few days with jaundice: a yellow discoloration of the whites of the eyes and the skin. Children may have mild infections without jaundice.
The infection is most commonly spread from person to person by infected feces. The feces are infectious for two weeks before the person becomes ill and for about a week after the jaundice appears. The greatest risk of spread occurs where there is a possibility of contact with untreated sewage. People traveling abroad to developing countries where sanitation is poor are therefore at risk of becoming infected. Infection can occur also after consuming raw shellfish, for example uncooked oysters.
Symptoms may appear within 2 weeks after contact with an infected person.
Minimizing the risk of Hepatitis A infection:
- Wash hands thoroughly after using the toilet and before preparing food or eating.
- Avoid swimming where water may be contaminated with untreated sewage.
- Avoid eating uncooked shellfish, such as oysters and mussels.
- If you are traveling to a developing country, protection can be given from the virus by a single injection at least 10 days before traveling.
If you have Hepatitis A symptoms:
HEPATITIS E (HEV)
- If the symptoms are severe and/or prolonged, seek medical advice. It is particularly important that young children and the elderly, and those already under medical supervision are treated.
- If a member of the household is suffering from vomiting and diarrhea, the infection could be passed on to others.
- Clean and disinfect the toilet, flush taps and door handle regularly with a disinfectant.
- Make sure you wash your hands after contact with an infected person.
- If you work as a food handler, make sure that you tell your employer and your health care provider.
Hepatitis E (HEV) was not recognized as a distinct human disease until 1980. Hepatitis E is caused by infection with the hepatitis E virus, a non-enveloped, positive-sense, single-stranded RNA virus. Although humans are considered the natural host for HEV, antibodies to HEV or closely related viruses have been
detected in primates and several other animal species.
HEV is transmitted via the fecal-oral route. Hepatitis E is a waterborne disease, and contaminated water or food supplies have been implicated in major outbreaks. Consumption of fecal contaminated drinking water has given rise to epidemics, and the ingestion of raw or uncooked shellfish has been the source of sporadic cases in endemic areas. There is a possibility of zoonotic spread of the virus, since several non-human primates, pigs, cows, sheep, goats and rodents are susceptible to infection. The risk factors for HEV infection are related poor sanitation in large areas of the world, and HEV shedding in feces.
Person-to-person transmission is uncommon. There is no evidence for sexual transmission or for transmission by transfusion.
The highest rates of infection occur in regions where low standards of sanitation promote the transmission of the virus. Epidemics of hepatitis E have been reported in Central and South-East Asia, North and West Africa, and in Mexico, especially where fecal contamination of drinking water is common. However, sporadic cases of hepatitis E have also been reported elsewhere and serological surveys suggest a global distribution of strains of hepatitis E of low pathogenicity.
In general, hepatitis E is a self-limiting viral infection followed by recovery. Prolonged viremia or fecal shedding are unusual and chronic infection does not occur. Occasionally, a fulminant form of hepatitis develops, with overall patient population mortality rates ranging between 0.5 to 4.0-percent. Fulminate hepatitis occurs more frequently in pregnancy and regularly induces a mortality rate of 20-percent among pregnant women in the 3rd trimester. The incubation period following exposure to HEV ranges from 3 to 8 weeks, with a mean of 40 days. The period of communicability is unknown. There are no chronic infections reported. Hepatitis E virus causes acute sporadic and epidemic viral hepatitis. Symptomatic HEV infection is most common in young adults aged 15 to 40 years. Although HEV infection is frequent in children, it is mostly asymptomatic or causes a very mild illness without jaundice (anicteric) that goes undiagnosed.
Typical signs and symptoms of hepatitis include jaundice (yellow discoloration of the skin and sclera of the eyes, dark urine and pale stools), anorexia (loss of appetite), an enlarged, tender liver (hepatomegaly), abdominal pain and tenderness, nausea and vomiting, and fever, although the disease may range in severity from subclinical to fulminant.
Since cases of hepatitis E are not clinically distinguishable from other types of acute viral hepatitis, diagnosis is made by blood tests which detect elevated antibody levels of specific antibodies to hepatitis E in the body or by reverse transcriptase polymerase chain reaction (RT-PCR). Unfortunately, such tests are
not widely available. Hepatitis E should be suspected in outbreaks of waterborne hepatitis occurring in developing countries, especially if the disease is more severe in pregnant women, or if hepatitis A has been excluded. If laboratory tests are not available, epidemiologic evidence can help in establishing a diagnosis.
Surveillance and control procedures should include provision of safe drinking water and proper disposal of sanitary waste, monitoring disease incidence, determination of source of infection and mode of transmission by epidemiologic investigation, detection of outbreaks, spread containment and vaccines, if available. At present, no commercially available vaccines exist for the prevention of hepatitis E. However, several studies for the development of an effective vaccine against hepatitis E are in progress.
As almost all HEV infections are spread by the fecal-oral route, good personal hygiene, high quality standards for public water supplies and proper disposal of sanitary waste have resulted in a low prevalence of HEV infections in many well developed societies. For travelers to highly endemic areas, the usual elementary food hygiene precautions are recommended. These include avoiding drinking water and/or ice of unknown purity and eating uncooked shellfish, uncooked fruits or vegetables that are not peeled or prepared by the traveler.
Hepatitis E is a viral disease, and as such, antibiotics are of no value in the treatment of the infection. There is no hyperimmune E globulin available for pre- or post-exposure prophylaxis. HEV infections are usually self-limited, and hospitalization is generally not required. No available therapy is capable of
altering the course of acute infection. As no specific therapy is capable of altering the course of acute hepatitis E infection, prevention is the most effective approach against the disease. Hospitalization is required for fulminant hepatitis and should be considered for infected pregnant women.
Norwalk virus is a very common virus that can be transmitted in food and water, and causes many cases of nausea, fever, headache, stomach ache, vomiting, and diarrhea in both children and adults. The Norwalk virus is getting a reputation as the "cruise ship virus" because of the great number of recent shipboard outbreaks. The symptoms usually start 1 to 2 days after infection and last from 1 to 10 days.
Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. Norovirus was recently approved as the official genus name for the group of viruses provisionally described as "Norwalk-like viruses" (NLV). This group of viruses has also been referred to as caliciviruses (because of their virus family name) and as small round structured viruses, or SRSVs (because of their morphologic features). Another genus of the calicivirus family that can cause gastroenteritis in humans is Sapovirus, formerly described as "Sapporo-like virus" (SLV) and sometimes referred to as classic or typical calicivirus.
Noroviruses are named after the original strain "Norwalk virus," which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. Currently, there are at least five norovirus genogroups (GI, GII, GIII, GIV and GV), which in turn are divided into at least 31 genetic clusters.
SIGNS & SYMPTOMS
The incubation period for norovirus-associated gastroenteritis in humans is usually between 24 and 48 hours (median in outbreaks 33 to 36 hours), but cases can occur within 12 hours of exposure. Norovirus infection usually presents as acute-onset vomiting, watery non-bloody diarrhea with abdominal cramps, and nausea. Low-grade fever also occasionally occurs, and vomiting is more common in children. Dehydration is the most common complication, especially among the young and elderly, and may require medical attention. Symptoms usually last 24 to 60 hours. Recovery is usually complete and there is no evidence of any serious long-term sequela. Studies with volunteers given stool filtrates have shown that asymptomatic infection may occur in as many as 30-percent of infections, although the role of asymptomatic infection in norovirus transmission is not well understood.
Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct person-to-person spread. Environmental and fomite contamination may also act as a source of infection. Good evidence exists for transmission due to aerosolization of vomitus that presumably results in droplets contaminating surfaces or entering the oral mucosa and being swallowed. No evidence suggests that infection occurs through the respiratory system.
Noroviruses are highly contagious and as few as 10 viral particles may be sufficient to infect an individual. During outbreaks of norovirus gastroenteritis, several modes of transmission have been documented; for example, initial foodborne transmission in a restaurant, followed by secondary person-to-person
transmission to household contacts. Although presymptomatic viral shedding may occur, shedding usually begins with onset of symptoms and may continue for 2 weeks after recovery. It is unclear to what extent viral shedding over 72 hours after recovery signifies continued infectivity.
Mechanisms of immunity to norovirus are unclear. It appears that immunity may be strain-specific and lasts only a few months; therefore, given the genetic variability of noroviruses, individuals are likely to be repeatedly infected throughout their lifetimes. This may explain the high attack rates in all ages reported in outbreaks. Recent evidence also suggests that susceptibility to infection may be genetically determined, with people of blood group O being at greatest risk for severe infection.
The CDC estimates that 23 million cases of acute gastroenteritis are due to norovirus infection, and it is now thought that at least 50 percent of all foodborne outbreaks of gastroenteritis can be attributed to noroviruses. Among the 232 outbreaks of norovirus illness reported to CDC from July 1997 to June 2000, 57 percent were foodborne, 16-percent were due to person-to-person spread, and 3-percent were waterborne; in 23-percent of outbreaks, the cause of transmission was not determined. In this study, common settings for outbreaks include restaurants and catered meals (36-percent), nursing homes (23-percent), schools (13-percent), and vacation settings or cruise ships (10-percent).
Most foodborne outbreaks of norovirus illness are likely to arise though direct contamination of food by a food handler immediately before its consumption. Outbreaks have frequently been associated with consumption of cold foods, including various salads, sandwiches, and bakery products. Liquid items (e.g., salad dressing or cake icing) that allow virus to mix evenly are often implicated as a cause of outbreaks. Food can also be contaminated at its source, and oysters from contaminated waters have been associated with widespread outbreaks of gastroenteritis. Other foods, including raspberries and salads, have been contaminated before widespread distribution and subsequently caused extensive outbreaks.
Waterborne outbreaks of norovirus disease in community settings have often been caused by sewage contamination of wells and recreational water.
HUMAN: In the last 10 years, diagnosis of norovirus as cause of outbreaks of acute gastroenteritis has improved with the increasing use of the reverse transcriptase polymerase chain reaction (RT-PCR). Currently, state public health laboratories of 47 states have the capability to test for noroviruses by (realtime) RT-PCR. RT-PCR detects the norovirus RNA and can be used to test stool and emesis samples, as well as environmental swabs in special studies. Identification of the virus can be best made from stool specimens taken within 48 to 72 hours after onset of symptoms, although good results can be obtained by using RT-PCR on samples taken as long as 5 days after symptom onset. Virus can sometimes be found in stool samples taken as late as 2 weeks after recovery.
Older methods for diagnosis include direct and immune electron microscopy of fecal specimens, and detection of a fourfold increase of specific antibodies in acute- and convalescent-phase blood samples. Several commercially available enzyme-linked immunosorbent assays for detection of virus in stools have been developed but await evaluation further evaluation regarding sensitivity and specificity.
Sequencing of norovirus strains found in clinical and environmental samples has greatly helped in conducting epidemiologic investigations by linking cases to each other and to a common source and by differentiating outbreaks that were mistakenly connected. Sequences can be entered into CaliciNet, a recently developed sequence database on the basis of the PulseNet model. In the next years CaliciNet will be further implemented to be able to help to determine links (e.g., norovirus contaminated foods) between outbreaks across the U.S.
In addition to microbiological techniques, several epidemiologic criteria have been proposed for use in determining whether an outbreak of gastroenteritis is of viral origin. Kaplan's criteria for this purpose are as follows: 1) a mean (or median) illness duration of 12 to 60 hours, 2) a mean (or median) incubation
period of 24 to 48 hours, 3) more than 50-percent of people with vomiting, and 4) no bacterial agent previously found. Although quite specific, these criteria are not very sensitive, and therefore the possibility of a viral etiology should not be discarded if the criteria are not met.
ENVIRONMENTAL: Methods to recover and detect virus in food need to be adapted for each food substance; these have been only rarely used, with the exception of assays to detect virus in shellfish. Drinking water can be tested for noroviruses by using RT-PCR when large (10-100 L) volumes of water are processed through specially designed filters.
No specific therapy exists for norovirus gastroenteritis. Symptomatic therapy consists of replacing fluid losses and correcting electrolyte disturbances through oral and intravenous fluid administration.
Prevention of foodborne norovirus disease is based on the provision of safe food and water. Noroviruses are relatively resistant to environmental challenge: they are able to survive freezing, temperatures as high as 60°C, and have even been associated with illness after being steamed in shellfish. Moreover,
noroviruses can survive in up to 10 ppm chlorine, well in excess of levels routinely present in public water systems. Despite these features, it is likely that relatively simple measures, such as correct handling of cold foods, strict hand washing after using the bathroom and before handling food items, and paid sick leave, may substantially reduce foodborne transmission of noroviruses. Prevention of norovirus disease spread via droplets from vomitus (person to person transmission) should focus on methods to limit transmission including isolation precautions (e.g., cohort sick patients in a healthcare facility) and environmental disinfection.