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PURDUE AGRICULTURE

FOOD ANIMAL EDUCATION NETWORK

Proper Preparation is Essential for Food Safety

Susan Hayes and Paul Ebner

The Centers for Disease Control and Prevention estimate that every year, roughly 5,000 U.S. deaths are caused by foodborne illnesses. Another 50 million people become ill, and approximately 325,000 are hospitalized. No food production process is perfect, and because food products cannot be guaranteed to be pathogen-free, risk is always present. However, this risk becomes negligible if proper precautions are taken during food preparation. The purpose of this paper is to discuss some common causes of foodborne infections and to describe several food preparation techniques that can significantly lower the risk of acquiring foodborne illnesses. Self-education about potentially harmful organisms can be a useful tool in avoiding foodborne illnesses. When armed with knowledge about how these organisms survive, thrive, and spread, avoiding illness becomes a fairly easy task. Foodborne illnesses typically stem from three categories of pathogens: bacteria, viruses and parasites. Even though most of these organisms are microscopic and cannot be seen by the naked eye, we can certainly take measures during food preparation to prevent them from harming us.

Bacteria

Thousands of species of bacteria are known to exist in the world. However, only a small group of these bacteria are known to cause illnesses in humans via the consumption of contaminated food.

One of the most notorious bacterial foodborne pathogens is E. coli. Though thousands of varieties of these bacteria exist, the one most often talked about is E. coli O157:H7, sometimes called STEC because it produces what is called Shiga toxin (“STEC” = Shiga toxin producing E. coli). Symptoms of an STEC infection include stomach cramps, diarrhea and vomiting. There are approximately 265,000 estimated cases of E. coli-associated foodborne illnesses in the U.S. each year (Table 1). The main concern with STEC infections is that in 5 to 10 percent of diagnosed cases, people develop a condition called hemolytic uremic syndrome (HUS), which can be life-threatening. STEC infections are spread via consumption of contaminated food, raw milk or dirty water. Special attention should be taken when both preparing and cooking hamburgers, as STEC often are associated with ground beef.

Campylobacter is another common species of bacteria capable of causing foodborne illness. Campylobacter infections (campylobacteriosis; approximately 2.4 million cases annually in the U.S.; Table 1) cause symptoms of diarrhea, cramping, abdominal pain and fever that typically appear two to five days after exposure to the bacteria and last about one week. Most cases are linked to eating raw or undercooked poultry or from cross-contamination by these products to other food. Therefore, it is essential to clean all surfaces that have been in contact with uncooked chicken or turkey. Infections can be avoided by cooking all poultry products thoroughly until the meat has lost its pink color and juices run clear.

Infections with Salmonella, another bacterial species, are called salmonellosis. Symptoms of salmonellosis are similar to those of campylobacteriosis; however, most people do not require treatment to become well again. To avoid infection, do not eat undercooked or raw eggs, milk, meat or poultry. In addition, washing hands after handling reptiles is important, since these animals frequently carry Salmonella. The Centers for Disease Control and Prevention estimate that there are 1.4 million cases of salmonellosis in the U.S. each year (Table 1).

Clostridia should also be noted as a common foodborne pathogen. Like many bacteria, this group has a special feature that allows it to survive in adverse conditions. Clostridia have the ability to form spores, which permit them to live in a dormant state until environmental conditions are more favorable for their growth. There are two major types of Clostridia: Clostridium perfringens and Clostridium botulinum. Most clostridial infections are cause by Clostridium perfringens. A much smaller, but often more serious, number of infections are caused by Clostridium botulinum, which produces the botulinum toxin (i.e., botox). Among approximately 145 cases occuring each year in the U.S., about 15% are foodborne. Most outbreaks are caused by foods canned at home, particularly those with low acid content. The botulinum toxin causes muscle paralysis, which can become very serious if not treated, such as in cases involving respiratory failure. In addition to basic food preparation guidelines, people who eat canned foods should always boil the food for 10 minutes prior to consumption.

Listeria monocytogenes, which causes listeriosis, usually affects older adults, pregnant women or those with compromised immune systems. People outside of those groups rarely are infected. Listeria have the special capability to grow in some foods in colder environments, including the refrigerator. Contamination of ready-to-eat food products sometimes takes place after factory cooking but before packaging. Thus, Listeria can be a large problem in food processing factories. In addition to following the basic food guidelines presented in this paper, people can reduce the risk of listeriosis by making sure their refrigerators are clean and that the temperature is set at 40 F or lower.

Viruses

In addition to bacteria, some viruses also can cause foodborne diseases. The most common disease-causing foodborne viruses include Hepatitis A, Norovirus and Rotavirus.

Hepatitis A is spread person-to-person by ingestion of fecal matter (i.e., the fecal-oral route). The virus usually is contracted through food or water that has come in contact with the feces of an infected person. In rare cases, infections can lead to liver disease. The number of Hepatitis A cases in the U.S. has dropped significantly in recent years because of the widespread use of an effective Hepatitis A vaccine. The Centers for Disease Control and Prevention estimate that there are still approximately 20,000 new Hepatitis A infections in the U.S. each year (Table 1).

Another dangerous virus, Norovirus, causes more than 20 million gastroenteritis cases in the U.S. every year -- almost half the total number of foodborne illness cases. Beginning with sudden symptoms of nausea, stomach cramping, diarrhea and vomiting, the infection usually subsides in about one or two days. Like Hepatitis A, Norovirus is spread person-to-person via the fecal-oral route and can be transmitted rapidly in crowded settings such as cruise ships, day cares and hotels. To prevent its spread, all contaminated surfaces should be cleaned and then disinfected with a bleach-based cleaning product after any episode of illness. Soiled items such as clothing or linens should be handled cautiously and washed thoroughly to prevent spread of the virus.

Rotavirus is a primary cause of severe diarrhea in infants and small children. Since the introduction of a rotavirus vaccine in 2006, the number of cases reported each year has significantly decreased. Before the vaccine was available, the virus was responsible for approximately 500,000 worldwide deaths in children under 5 years of age each year. The virus is transmitted person-to-person mainly by hand-to-hand contact, but food can become contaminated if it is prepared by an individual with a rotavirus infection. Fortunately, disease can be prevented by vaccination.

Parasites

Parasites make up the remainder of the organisms that typically cause foodborne illnesses. Many varieties exist but the most common are cryptosporidium, giardia and toxoplasma.

Commonly known as “Crypto,” Cryptosporidium parvum is a protozoan parasite that causes cryptosporidiosis, a condition associated with severe diarrhea. This particular parasite has an outer shell of protection that enables it to survive exposure to chlorine disinfectants, as well as exposure outside the body for long amounts of time. Transmitted via the fecal-oral route, the disease (approximately 748,000 cases per year in the U.S.; Table 1) typically is acquired by drinking water that contains the parasite.

Giardia is a parasite that typically resides in water, food, soil or on surfaces that have been contaminated with fecal matter from an infected animal. There are approximately 2.5 million cases of giardiosis each year in the U.S. (Table 1). Giardia also has a protective outer covering that enables it to tolerate disinfection by chlorine, and to live outside the body for signigicant amounts of time. If in doubt about the safety of a water source, tap water should be heated for one minute at a boil or bottled water used instead. Untreated water from recreational areas, lakes, rivers or streams should never be swallowed.

Toxoplasmosis, an infection caused by the Toxoplasma parasite, is a primary cause of foodborne illness-related death in the U.S. Though tens of millions of people in the U.S. carry this parasite, their immune systems usually are hardy enough that the parasite cannot cause illness and they remain asymptomatic. The first step to preventing infection is to follow the basic safety measures described in this article, including proper hand washing, cooking to safe temperatures, and food handling. Cats can become infected with this pathogen without showing any sign of infection. Therefore, to reduce risk of toxoplasmosis from the environment, outdoor sandboxes should be covered and cats fed only dried or canned commercial food —never any raw meat. Additionally, cats should be kept indoors, if possible, and litter boxes should be changed daily.

Prevention

The risk of foodborne diseases can be greatly reduced by taking the following five basic precautions in food handling and preparation: clean, separate, cook, chill and report. Consumers can protect themselves by properly following these simple safety measures that significantly decrease the possibility of acquiring foodborne illness.

Cleaning is the most obvious and effective tool for preventing foodborne illnesses. First and foremost, any person involved in food preparation should always wash their hands with soap and water for at least 20 seconds before handling any food, utensils or containers. As a general rule, all surfaces that come in contact with food should be cleaned, including refrigerator shelves and lunchboxes. Also, because many pathogens can be spread via the fecal-oral route, any person suffering from a diarrheal illness, has recently changed a baby’s diaper or been around animals either should clean their hands especially well or avoid preparing food at that time. When preparing fruits and vegetables, food always should be washed with running tap water before doing anything else. Bacteria thrive on the cut surfaces of produce, so it is important to remove the outermost layer of foods like lettuce or cabbage, and to prevent contamination while slicing any type of produce.

The spread of foodborne illnesses often is the result of cross-contamination. Therefore, it is very important to separate products when preparing food. While cooking, frequently wash all surfaces, including hands, cutting boards and utensils to avoid cross-contamination. Especially while cooking with raw meat or poultry, clean all contaminated surfaces before they contact any other food. Cooked meat should be placed on a clean dish, not returned to the dish that previously held uncooked meat.

Always cook eggs, meat and poultry thoroughly, using a thermometer, when possible, to measure internal temperatures. This will ensure that the meat has reached a temperature sufficient to kill any dangerous bacteria that may be present. Whole meats should reach an internal temperature of 145 F; ground meats, 160F; and poultry, 165F. Because meat continues to cook after being removed from heat, note the importance of allowing several minutes for the meat to finish cooking. Eggs should be heated until the yolk becomes firm.

Though proper food preparation is essential to prevent foodborne diseases, proper care of leftovers is of equal importance. Any leftover food that will not be eaten within two hours after a meal should be refrigerated quickly, since some types of bacteria grow rapidly at room temperature.

Finally, reporting plays a major role in keeping the public healthy and safe. The job of the local public health department is to protect consumers, so any suspected foodborne illnesses should be reported to them as soon as possible. Frequently, outbreaks are detected this way, so citizen cooperation with public health officials is vital, whether those reporting are healthy or ill.

Information and data for this paper were compiled from the U.S. Centers for Disease Control, The Food Safety Inspection Service of the U.S. Department of Agriculture and the U.S. Food and Drug Administration.
 

Table 1. Estimated yearly number of foodborne illnesses per pathogen in the United States. Data collected by the U.S. Centers for Disease Control and Prevention.

Pathogen

Estimated cases/yr. in U.S.

Mode of transmission

Usual vehicles of transmission

STEC

265,000

Fecal-oral route

Raw meats, dairy products or juices; contaminated water

Campylobacter

2.4 million

Some foods, especially poultry; fecal-oral route

Raw/undercooked poultry; unpasteurized milk; contaminated water; infected pet feces

Salmonella

1.4 million

Fecal-oral route

Contaminated food or water; contact with infected animals

Clostridium botulinum

145

Ingestion or inhalation of toxin

Home-canned foods; honey (infants only)

Listeria monocytogenes

1,600

Ingestion of contaminated food

Raw food and food contaminated after cooking or processing; raw milk and cheese

Hepatitis A Virus

20,000

Fecal-oral route; ingestion of contaminated food or water

Contaminated food or water

Norovirus

5.4 million

Person-to-person; ingestion of contaminated food or water; touching mouth with contaminated hands

Fomites; contaminated food or water; infected fecal matter and vomit

Rotavirus

fewer than 70,000

Fecal-oral route; person-to-person contact; fomites

Feces of infected persons; contaminated fomites or food

Cryptosporidium parvum

748,000

Fecal-oral route

Contaminated water

Giardia

2.5 million

Fecal-oral route

Contaminated water and sometimes food

Toxoplasma

22.5% of the population under 12 years of age

Ingestion of undercooked, contaminated meat

Undercooked meat, especially pork, lamb, venison

 

Paul Ebner, PhD
Associate Professor
Dept. of Animal Sciences
pebner@purdue.edu


 

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