Pathogens

Bacteria and viruses are the most common causes of food poisoning. The symptoms and severity of food poisoning vary, depending on which bacteria or virus has contaminated the food.  Eggs have been found to be 90% sterile when laid. However, eggs have the potential to become contaminated with bacteria from the hen’s intestinal tract, feces, and from the surrounding environment.

While bacteria and viruses are naturally present on any raw food, there are steps we can take while preparing our food to ensure our food is safe.  Four important things that everyone should practice when preparing any type of food is to:

CLEAN: Wash hands and surfaces often.

SEPARATE: Don't cross-contaminate foods. 

COOK: Cook to proper temperature.  For optimal safety, eggs should always be cooked until both the yolk and whites are firm. 

STORE: Keep cold food cold and hot food hot and always refrigerate promptly.  Bacteria multiply rapidly between 40 °F and 140 °F. To keep food out of this "Danger Zone," keep cold food cold and hot food hot.

Only a small few of the many types of bacteria and viruses are potentially pathogenic, or disease-causing. The bacteria’s listed below all have the ability to affect the safety of the egg that could result in human illness and, as such, are pathogens that the U.S. egg industry vigilantly gaurds against.  Despite our best efforts, there is always a chance that a raw food can be contaminated and it is important to always thoroughly cook eggs to destroy all pathogens.

Salmonella

Salmonella lives in the intestinal track of humans and animals, especially birds. Salmonella can be passed to humans through the consumption of contaminated foods that have been in contact with unwashed hands, raw meat or poultry, eggs, seafood, milk, or by coming in contact with contaminated animal feces.

  • The two most common types of Salmonella in the United States are Salmonella Enteritidis and Salmonella Typhimurium, which account for half of all human infections in the U.S.
  • Salmonella species cause the infection salmonellosis.
  • Salmonellosis causes diarrhea, abdominal cramps and fever within eight to 72 hours after ingestion of contaminated food. Additional symptoms may include chills, headache, nausea and vomiting. All symptoms usually disappear within four to seven days.

Aeromonas hydrophila

Aeromonas hydrophila is a bacteria present in all freshwater and salty water environments. Some strains of A. hydrophila are capable of causing illness in fish and amphibians as well as in humans, who may acquire infections through open wounds or by ingestion of a sufficient number of the organisms in food or water.

  • A. hydrophila has frequently been found in fish and shellfish as well as in market samples of red meats and poultry.
  • A. hydrophila may cause intestinal inflammation in healthy individuals.

To protect against the possibility of Aeromonas in the water used to rinse eggs, processing plants use extremely hot temperatures and sanitizing agents to clean and disinfect both the eggs and water.

Avian Influenza

Avian influenza (AI) is a viral infection caused by avian influenza viruses. All known subtypes of influenza A viruses can occur naturally among birds and are very contagious. Wild birds carry the viruses in their intestines, but usually do not get sick from them. However, domesticated birds, including chickens, ducks and turkeys can become very sick and can die if they catch the virus.

  • Infected birds shed the virus in their saliva, nasal secretions, and feces.
  • Domesticated birds may become infected with avian influenza virus through direct contact with contaminated wild birds or other poultry, or through contact with surfaces or materials that have been contaminated with the virus.
  • There are two main forms of AI, low pathogenic and high pathogenic.
    • Low pathogenic AI has the potential to go undetected and only causes mild symptoms.
    • High pathogenic AI spreads more rapidly throughout a flock than the low pathogenic form causing death usually within 48 hours.

Generally, avian influenza viruses are found chiefly in birds, but infections have been found to occur in humans. The risk from avian influenza is generally low to most people.

  • Most cases of avian influenza infection in humans have resulted from contact with infected poultry or surfaces contaminated with fluids from infected birds.
  • Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases and other severe and life-threatening complications.

Bacillus cereus

Bacillus cereus is a bacteria that can both be harmful to humans and cause foodborne illness or be beneficial for animals in the form of probiotics.

  • B. cereus can be associated with a wide variety of foods including meats, milk, vegetables, fish, potatoes, pasta, and cheese products. Also, food mixtures such as sauces, puddings, soups, casseroles, pastries and salads have frequently been incriminated in B. cereus food poisoning outbreaks.
  • All people are believed to be susceptible to B. cereus food poisoning.

Campylobacter

Campylobacter is typically found in the reproductive organs, intestinal tract and oral cavity of humans and animals.

  • Humans can become ill by the ingestion of unpasteurized milk, contaminated water or vegetables, raw or undercooked meat or poultry, or by coming in contact with feces from infected humans and domestic pets.
  • Campylobacter cause the infectious disease campylobacterosis. Symptoms of campylobacteriosis typically include headache, muscle pain and fever that is followed by watery or bloody diarrhea, nausea and abdominal pain. These symptoms occur two to five days after ingestion and can last from three to ten days.

Campylobacter, while it can be found in the reproductive organs and intestinal tract of the hens, is very rarely found in connection to shell eggs. Most campylobacter infections associated with poultry occur with meat products.

Listeria monocytogenes

Listeria monocytogenes is found in both wild and domestic mammals as well as birds and some species of fish and shellfish. It also can be isolated from soil, silage and other environmental sources.

  • L. monocytogenes is hardy and has been associated with such foods as raw milk, supposedly pasteurized fluid milk, cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (all types), as well as raw and smoked fish.
  • It’s ability to grow at temperatures as low as 3°C permits multiplication in refrigerated foods.

Listeria monocytogenes can be found in both the egg processing plant environment as well as in the egg itself.

Staphylococcus aureus

Staphylococcus aureus is a gram positive round bacterium capable of producing a toxin that causes illness in humans. Staphylococcus aureus exists in air, dust, sewage, water, milk and food or on food equipment, environmental surfaces, humans and animals. Foods that are frequently involved with 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, chocolate eclairs and sandwich fillings
  • milk and dairy products

Staphylococcal food poisoning occurs when humans ingest food contaminated with the toxin. The onset of symptoms in staphylococcal food poisoning usually occurs rapidly.

  • The most common symptoms of this type of food poisoning are nausea, vomiting, retching, abdominal cramping and fatigue. In more severe cases, headache, muscle cramping, and transient changes in blood pressure and pulse rate may occur.
  • Recovery from this type of food poisoning generally takes two days. It is not unusual for complete recovery to take three days and sometimes longer in severe cases.

Staphylococcus aureus is also present in the nasal passages, throats and on the hair and skin of both humans and animals. 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.