Preventing Bacteria in Chicken Meat and Eggs

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Although most eggs produced in clean conditions and promptly refrigerated after collection pose little health risk, proper precautions should be taken to ensure that eggs remain fresh, delicious and bacteria-free.
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Suspect food-borne illness? Use this chart to assess your symptoms and identify possible bacterial infections.
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"The Chicken Health Handbook: A Complete Guide to Maximizing Flock Health and Dealing with Disease" by Gail Damerow is full of detailed and accessible information to help chicken owners keep their birds disease-free and productive.

The Chicken Health Handbook: A Complete Guide to Maximizing Flock Health and Dealing with Disease (Storey Publishing, 2015) by Gail Damerow is the ultimate resource for raising healthy chickens. This second edition is updated and revised, featuring full-color photographs and detailed illustrations to assist chicken owners with a variety of health concerns. Damerow, the country’s most widely recognized authority on the subject, explains how to keep chicken meat and eggs free from contaminants and bacteria.

You can purchase this book from the Capper’s Farmer store: The Chicken Health Handbook.

Meat and Egg Contaminants

One of the reasons people raise their own food-producing chickens, even though doing so costs more than purchasing store-bought meat and eggs, is their concerns about pesticide and herbicide residues, antibiotics, and microbial contaminants in industrially produced poultry products.

Pesticides and herbicides are used on most feed crops that make up chicken rations. Unless you have a source of so-called organic rations, your eggs and chicken meat will contain no fewer residues from pesticides and herbicides than industrially produced meat, which in any case is extremely low. Residues can also come from treating chickens or their facilities for external parasites using chemicals that enter a chicken’s body by inhalation or through the skin. Chemical treatments should therefore be used with care, and cleanliness is far preferable.

Antibiotics at low levels are used industrially to make meat birds reach market weights faster with lower feed costs. Antibiotics are not routinely given to industrial layers but are occasionally used as needed to control disease. You can easily avoid antibiotics in homegrown meat by not making drugs part of your management routine and by observing the withdrawal time for any drug you do use for therapeutic purposes.

Pathogenic microbes pose the greatest threat among contaminants in poultry meat or eggs, especially those that are industrially produced, since large-scale production and processing lend themselves to unsanitary practices.

Homegrown meat birds, by contrast, are usually killed and cleaned individually, are rinsed under a running faucet (rather than in a vat of rapidly contaminated water), and are refrigerated promptly. Similarly, homegrown eggs are exposed to fewer sources of contamination. Nevertheless, remaining aware of the dangers of contamination is an important step toward avoiding them.

Food-Borne Bacteria

If meat or eggs are held at room temperature for too long, any bacteria present will proliferate. Some multiply more rapidly than others. Since there’s no way to tell whether or not bacteria are present, you can’t go wrong if you always handle meat and eggs as if they were contaminated.

In a healthy human adult, bacterial food poisoning is typically little more than an annoyance. In a young child, an elderly person, or someone with a compromised immune system, however, bacterial food poisoning can be serious or even fatal. General symptoms are loss of appetite, nausea, vomiting, abdominal cramps, and diarrhea that comes on suddenly. A clue that it is a food-borne problem is when illness strikes a group of people who have shared a meal.

Most cases are resolved with bed rest and plenty of fluids. For many people the most serious consequence is loss of body fluids and electrolytes. Since symptoms resemble the flu, most cases go untreated and end in spontaneous recovery. Unless the illness is complicated by other factors, antibiotics may be of little help and may actually make matters worse. With salmonella, for instance, antibiotic treatment prolongs the period during which the recovered person remains a carrier, and is associated with relapse. Antibiotics also kill the good gut flora that would have helped the patient recover.

Unless the person requires hospitalization, the best course of action is to rest and replace lost fluids and electrolytes. The most common causes of bacterial food poisoning are campylobacter, E. coli, and salmonella. Some food-borne bacteria produce toxins that inhibit nutrient absorption, while others are infective — causing disease by invading the intestine wall. Some work both ways.


You would have a hard time finding meat, eggs, or any other food that did not harbor one of the 2,500 known strains of salmonella bacteria. S. Enteriditis is the version that causes food poisoning outbreaks periodically reported in the news. No one knows exactly how many people experience salmonella poisoning each year, since mild cases are rarely reported. Of the 40,000 annual cases that are reported, only about 5 percent have been traced to chickens. Poultry disease experts once believed S. Enteriditis infected an egg through the shell after the egg was laid and that frequent egg collection and disinfection would minimize contamination. In the 1980s they discovered that salmonella bacteria in hens’ ovaries can infect eggs before they are laid. Since then, S. Enteriditis bacteria have become more common in both chickens and humans, as well as becoming resistant to antibiotics. No one can guess how commonly salmonella bacteria occur in eggs from backyard chickens. According to the Centers for Disease Control and Prevention, only about one in 5,000 to 10,000 industrially produced eggs is contaminated. Despite alarmist press coverage, experts claim your chance of getting salmonellosis from those eggs is only about one in two million. Illness in a healthy person requires eating a large number of bacteria. Further, most cases occur not in homes but in restaurants, schools, hospitals, and other institutions where eggs are mixed in large batches and may not be cooked long enough or may sit on a counter too long, allowing any bacteria present to multiply.

Salmonella bacteria concentrate in the yolk. They may also be present in chicken meat, typically from contamination with fecal matter from the intestines during butchering. Preventing illness is a matter of careful sanitation during butchering, combined with serving chicken meat well done. Thoroughly cooked chicken reaches a temperature well above the 142 degrees F (61 degrees C) necessary to kill salmonella. Most people who experience salmonella poisoning never know it, believing instead that they have an upset stomach or a mild case of flu. Symptoms begin 12 to 74 hours after eating contaminated food, which tastes and smells normal. Symptoms include nausea, fever, abdominal cramps, and diarrhea. Most infections are relatively mild, and most people recover in a week or less without treatment, as long as they avoid dehydration by drinking lots of fluids.

A serious infection, however, can spread from the intestines to the bloodstream and other body sites, resulting in death, especially among infants, the elderly, anyone with an impaired immune system, a patient undergoing treatment with antibiotics (which remove beneficial bacteria from the intestines, clearing the way for disease-causing bacteria), or an ulcer patient taking antacids (which reduce bacteria-killing stomach acids). Hospitalization is needed if symptoms persist or diarrhea is severe or accompanied by high fever, weakness, or disorientation.


Although it gets less press than salmonellosis, campylobacteriosis is the world’s leading food-borne pathogen and the most common cause of diarrheal illness in humans. Of the three species that cause human disease, Campylobacter jejuni — the cause of campylobacteriosis in chickens — is identified more than 90 percent of the time, and chicken meat has been identified as the main source of human illness.

Unlike salmonellosis, campylobacteriosis is not transmitted through contaminated eggs. People become ill by handling infected birds (campylobacteriosis is an occupational hazard in poultry processing plants) or by eating undercooked infected chicken meat.

The bacteria produce a toxin that irritates the lining of the intestine, causing abdominal cramps and watery, sometimes bloody diarrhea, occasionally accompanied by a fever ranging from 100 F to 104 F (38 C to 40 C). Usually the illness goes away on its own, but an infant, an elderly person, or someone with compromised immunity may require medical treatment.

No one can say how common these bacteria are in backyard flocks, but they are of growing concern because of their prevalence in industrially produced poultry and their increasing resistance to antibiotics. On the other hand, the stress of rough handling and being transported to a distant processor dramatically increases the presence of campylobacter in the chickens’ meat, compared to backyard chickens that are humanely handled at home. At any rate, you can avoid campylobacteriosis by observing basic hygiene precautions and by not eating raw or undercooked chicken meat.

Don’t Swallow the Bug

A person can get salmonellosis or campylobacteriosis directly from handling an infected chicken by inadvertently swallowing bacteria, as can happen if you eat (or smoke) while working with or around chickens or fail to thoroughly wash your hands afterward. Children are especially susceptible unless they are trained to keep their fingers out of their mouths, avoid kissing chicks and chickens, and always wash hands after visiting the family flock.

Escherichia Coli

Although it rarely results from eating properly processed homegrown chicken, Escherichia coli (E. coli) infection is included here because it is of increasing concern to people who work with industrially produced chickens routinely treated with antibiotics, backyarders who persist in using antibiotics to prevent disease in their flocks, and people who eat undercooked contaminated chicken meat. Studies have linked antibiotic treatment of chickens to the emergence of drug-resistant strains of E. coli and to an increasing number of difficult-to-treat human infections.

Of the many different types of E. coli bacteria existing throughout the environment, most are harmless, some are beneficial, and only a few will make you sick. Among the pathogenic types, some produce a toxin called Shiga (named after the bacteriologist who discovered it). Unlike with many disease-causing bacteria, ingesting only a tiny amount of E. coli can make you sick. Further, the bacteria spread easily from an infected person to others.

People who are at greatest risk for serious infection are children, pregnant women and their newborns, elderly adults, and anyone with a weak immune system. Signs of infection include severe abdominal cramps and diarrhea that may turn bloody within about 24 hours. E. coli can also cause a urinary tract infection, respiratory illness, bloodstream infection, kidney failure, and even death. Most infections are mild, however, clearing up on their own within about a week, and remain undiagnosed or unreported.

Avoidance includes thoroughly cooking chicken meat, especially if you are unsure about the sanitation procedures during butchering, and thoroughly washing your hands any time you may have come into contact with infected chickens or their droppings, or potentially contaminated chicken meat.

Egg Sanitation

A freshly laid egg is warm and moist and therefore attracts bacteria and molds that exist in the poultry environment. After leaving a hen’s warm body, the egg immediately starts to cool. As its contents contract, a vacuum is created that can draw bacteria and molds through the 6,000-plus pores in the shell, potentially causing egg spoilage and human illness.

Eggs produced in a clean environment, collected often, and promptly placed under refrigeration (after cracked or seriously soiled eggs are discarded) rarely pose a human health problem. Eggs that are slightly soiled with dirt or dried droppings should be dry-cleaned with fine sandpaper. Improperly washing them can do more harm than good.

Eggs produced in a not-so-clean environment and those destined for market may need to be washed. Market eggs are often subjected to temperatures that are higher than desirable (causing bacteria and mold on the shell to multiply) and to repeated warming and cooling during transportation (drawing more microbes through the shell each time).

If you feel the need to wash eggs, use water that is 20 F (11 C) warmer than the eggs are; otherwise vacuum action may draw microorganisms through the shell or tiny cracks may develop in the shell that expose eggs to invasion by bacteria and molds. Wash eggs with detergent (not soap) to remove soil. Rinse them in water of the same temperature as the wash water, adding a sanitizer to reduce the number of microbes on the shell (a sanitizer won’t eliminate all bacteria and mold). If you wash a large number of eggs, change the wash and rinse solution often, since both can rapidly become contaminated.

Egg sanitizers are available from many poultry suppliers. A chlorine solution (such as 5.25 percent Clorox bleach) will not introduce an off odor or flavor when used at the rate of 1 tablespoon per gallon of water (2 mg/L). Dry eggs thoroughly before placing them in cartons, since wet shells will more readily pick up bacteria. If you are packaging the eggs for sale, check your state’s regulations regarding legally acceptable procedures for cleaning them.

Handling Meat Birds

When butchering your own chickens, select only plump, healthy-looking birds. Avoid rough handling and other forms of stress, which can both increase bacterial contamination and affect the meat’s taste and texture. To reduce the possibility of fecal contamination, hold the birds overnight without feed but with continuing access to drinking water.

Once each chicken is plucked and gutted, thoroughly rinse it in clear running water. Rapidly chill the birds in fresh cold water with plenty of ice before packaging them for refrigeration. Allow muscle (meat) to tenderize in the fridge for no less than 1 day and no more than 4 days, by which time it should be either cooked or frozen.

Egg Storage

Whether or not your fresh eggs need to be hustled into the refrigerator is a matter of some debate. Because of the possibility of salmonella poisoning, in 1990 the United States Food and Drug Administration decreed that shell eggs are a “potentially hazardous food.” Industrially produced eggs therefore must be washed and sanitized, remain under constant refrigeration from farm to consumer, and cooked thoroughly before being eaten.

Although backyard hens can, and occasionally do, get bacterial infections, keepers who take care to maintain a healthful environment are returning to the tradition of not refrigerating homegrown eggs. In 2013 the British-based firm Foodtest Laboratories stored unwashed eggs from healthy hens at room temperature generally considered to be 68 F/20 C) for 2 weeks, at the end of which the eggs remained bacteria-free. While eggs that have been washed should always be refrigerated, eggs that are clean when collected and remain unwashed to preserve their protective bloom may be kept at room temperature for up to 30 days.

However, consider this: The American Egg Board has determined that eggs age more in 1 day at room temperature than in 1 week in the fridge. So quality wise, 2-week-old countertop eggs compare to eggs that have been in the fridge for 14 weeks, and 30 days on the counter compares to 7 months in the fridge. Aging eggs may not be laden with bacteria, but they gradually become less appetizing, with runny whites and yolks that break easily.

Excerpted from The Chicken Health Handbook, 2nd Ed. (c) Gail Damerow. Photograph by (c) Elizabeth Cecil. Illustrations by (c) Bethany Caskey. Used with permission of Storey Publishing. Buy this book from our store:The Chicken Health Handbook.