Salmonella Outbreaks: Who's Watching the Hens?

The HWN Team | Insider
Salmonella Outbreaks: Who's Watching the Hens?

image by: Tim Green

Salmonella outbreaks will continue to occur despite new regulations aimed at minimizing hen and egg exposure. Stay egg smart. Forego those raw eggs in your next Caesar and don't forget to keep your reuseable bags clean!

The global incidence of foodborne disease is difficult to estimate according to WHO, but it has been reported that in 2005 alone 1.8 million people died from diarrheal diseases. A great proportion of these cases can be attributed to contamination of food and drinking water.1

The CDC estimates that roughly 1 in 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases and every year, approximately 42,000 cases of salmonellosis are reported in the United States and up to 400 persons die each year with acute salmonellosis. Children are the most likely to get salmonellosis. Because many milder cases are not diagnosed or reported, the actual number of infections may be twenty-nine or more times greater.2,3

Salmonellosis is a potentially life-threatening foodborne illness caused by the bacterium Salmonella. Because it is a serious health concern that can easily become an epidemic, salmonellosis is a “notifiable disease”, e.g. doctors are required to report its occurrence upon diagnosis “to local health departments in accordance with procedures established by each State. Infections can be traced based on a pathogen’s serotype and DNA fingerprint.”

Although Salmonellosis is caused by several species, Salmonella enteritidis is the usual culprit. Salmonella infection manifests as gastroenteritis, food poisoning or typhoid fever. Symptoms, which take up to 72 hours to appear, include vomiting, diarrhea, fever and abdominal cramps. Even after recovering from salmonellosis, those infected may still suffer from recurring joint pain and reactive arthritis.4

Contaminated food and beverages, especially water, are the main source of Salmonella infection. Contamination of eggs by Salmonella enteritidis occurs in the farms. A laying hen which is infected by the bacteria passes on the pathogen into the egg before it is laid. After it is laid, the bacteria can grow inside the uncracked, whole egg. “Shell egg” is a term used for the unopened whole shell egg to distinguish it from other egg products whose shells are removed for processing. The pathogen present in the egg is killed during cooking. However, the pathogen will persist and multiply in food with raw egg ingredients such as sauces, salad dressings and cake icings and cause foodborne illness.

According to a farm-to-table risk assessment of Salmonella enteritidis (SE) in eggs which was conducted by the FDA and the U.S. Department of Agriculture Food Safety and Inspection Service (FSIS): "we estimated that of the 47 billion shell eggs consumed annually as table eggs (eggs consumed as shell eggs, as opposed to eggs that are used to make egg products), 2.3 million are SE-positive, exposing a large number of people to the risk of illness".5

The 2010 outbreak was one of the largest salmonellosis outbreak since the CDC started its surveillance in the 1970's.6

A higher than usual incidence of salmonellosis was reported in several parts of the U.S. that covered 10 states. Hundreds of confirmed cases of salmonellosis were reported in at least 3 states California, Colorado and Minnesota.

The investigation by the CDC traced back the illnesses to 26 event clusters, mainly restaurants in 10 states. Further investigation indicated eggs as the most likely source of the pathogen as records show that eggs are the predominant source of Salmonella enteritidis. In 15 of the 26 restaurants investigated, the eggs were supplied by Wright County Egg based in Galt, Iowa. Another potential source of contaminated eggs was identified – the Hillandale Farms also based in Iowa. A total of 2,403 cases were reported from May 1 to August 25, 2010. Expected incidence during this period was 933. About half a billion shell eggs were recalled nationwide in at least 14 states.

Although the big egg recall occurred in August 2010, there were already reports of this strain of salmonella infection as early as May 2010. One may wonder why it took so long for the investigators to trace back the source of the Salmonella contamination. The problem is in the time lag between exposure, the onset of an illness and when it is reported, tested and confirmed. In the case of Salmonella it takes up to 72 hours for symptoms to manifest and another several days for testing. The average time lag is 2 to 3 weeks.7

Both farms are large egg producers with more 50,000 egg-laying hens in their facilities and are therefore covered under the Egg Safety Rule.  As reported in USA Today, Wright County Egg is owned by Austin "Jack" DeCoster whose farm operations have a long history of environmental, labor, health and animal welfare violations. DeCoster also has reported some financial connection to Hillandale Farms and he also owns Quality Egg, another company that supplies chicks and feeds.

According to a statement from Wright it isn't shipping any shell, or consumable, eggs until the FDA investigation is completed and in the future will sell only eggs that come from vaccinated hens. It said all its eggs "are cleaned and processed prior to being packed into cartons and held refrigerated at 45 degrees or below per FDA regulations. No exceptions." 

According to a Hillandale statement: "We are devastated that our eggs have been implicated in making people sick. We have never had a product recall in our 45-year history, and it flies in the face of our mission to provide wholesome, nutritious food for the American public. We regret that anyone might have become ill, and the concern and disruption this has caused our customers."

So, who's watching the hens?

In the U.S. the FDA is responsible for ensuring the safety of food that reaches American consumers. In the case of safety of eggs, the FDA updated safety procedures recently in the form of issuance of the Egg Safety Rule described in the a Federal Register document entitled Prevention of Salmonella Enteritidis in Shell Eggs During Production, Storage, and Transportation; Final Rule.8

Previous shell egg safety rules focused on refrigeration during transport and marketing to limit the growth of bacteria that may be inside an egg. The new rules focus on preventing contamination at the source – in the chicken farms - and are aimed at reducing the risk for Salmonella enteritidis contamination by almost 60%. The final rule on egg safety was issued by the FDA on July 9, 2009, with compliance dates set on July 9, 2010. By then, the 2010 outbreak had already occurred.

Was there a gap left as the local EQAPs audits prepared to pull out while the FDA and USDA were starting up? According to Sherri McGarry, emergency coordinator for the FDA's Center for Food Safety and Applied Nutrition, the new rule could have prevented the outbreak, but the FDA did not have the authority to inspect the affected farms before July 9, 2010.

To help prevent future outbreaks, the rule is required to be adopted by “ all egg producers with 3,000 or more laying hens whose shell eggs are not processed with a treatment, such as pasteurization, to ensure their safety.” This covers more than 4,000 large-scale farms in the U.S. with 3,000 or more egg-laying hens, accounting for 99% of the total egg production in the country. However, there are 65,000 smaller farms with less 3,000 laying hens not covered by the rule. These farms usually sell the eggs directly to consumers.

The new rule requires farms to have a Salmonella enteritidis (SE) prevention plan to reduce risk of contamination at the source including the following:

Procure pullets that are SE-monitored, or raise pullets under SE-monitored conditions.

Use a biosecurity program, meaning a program that includes limiting visitors, on the farm and in poultry houses; maintaining personnel and equipment practices that will protect against cross contamination from one poultry house to another; preventing stray poultry, wild birds, cats, and other animals from entering poultry houses; and prohibiting employees from keeping birds at home

Use a program to control rodents, flies, and other pests that includes monitoring for pest activity and removing debris and vegetation that may provide harborage for pests.

Clean and disinfect poultry houses before new laying hens are added, if an environmental or egg test was positive for SE during the life of the flock; cleaning and disinfecting must include removing all visible manure, dry cleaning to remove dust, feathers, and old feed, and disinfecting.

The new rule also requires FDA registration of all egg producers, routine SE test, proper recording keeping and documentation, with records that go back 12 months to be available within 24 hours of an official request. Additional requirements for refrigeration procedures and transport were also included in the new rule. Vaccination of chickens against Salmonella enteritidis was not included in the rule as there are currently no approved vaccines against this pathogen available.

Before the rule was in place, farm inspections and audits were conducted by voluntary state and industry egg quality assurance programs (EQAPs). Although they have helped in reducing contamination, the U.S. FDA believes implementation should be centralized under its authority “ to establish uniform, nationwide requirements to prevent SE in shell eggs during production, storage, and transportation.”  Thus, voluntary EQAP audits are no longer recognized under this rule. The FDA would work together with the U.S. Department of Agriculture in auditing for compliance.

But, there are some loopholes in the legislation that can lead to future outbreaks.

Specifically, producers who sell all their eggs directly to consumers or have less than 3,000 hens are not covered by the rule.

And, according to Bill Marler, a Seattle lawyer representing dozens of affected consumers: "This is sort of the classic example of where the USDA and FDA jurisdiction overlaps. The USDA is chickens and the chicken house, and the FDA is in charge of the eggs when they come out and the feed that comes in."

OK, what can we do to minimize salmonellosis infection?

The CDC gives the following advice:9

  • Keep eggs refrigerated at < 45° F (< 7° C) at all times.
  • Discard cracked or dirty eggs.
  • Wash hands, cooking utensils, and food preparation surfaces with soap and water after contact with raw eggs.
  • Eggs should be cooked until both the white and the yolk are firm and eaten promptly after cooking.
  • Do not keep eggs warm or at room temperature for more than 2 hours.
  • Refrigerate unused or leftover egg- containing foods promptly.
  • Avoid eating raw eggs.
  • Avoid restaurant dishes made with raw or undercooked, unpasteurized eggs. Restaurants should use pasteurized eggs in any recipe (such as Hollandaise sauce or Caesar salad dressing) that calls for raw eggs.
  • Consumption of raw or undercooked eggs should be avoided, especially by young children, elderly persons, and persons with weakened immune systems or debilitating illness.

Lastly, always use clean containers to carry your food including your reusuable grocery bag, as well as keeping track of any recalls in your area: FDA Product Recalls and Egg Safety Center.

The Bottom Line

You may never know when the next recall will occur. In the meantime, while inspectors and producers sort out which comes first 'the chicken or the salmonella' stay egg smart. And don't forget to keep your reusuable grocery tote clean!

Published September 3, 2010, updated June 21, 2012


  1. Food safety and foodborne illness, WHO March 2007
  2. 2011 Estimates of Foodborne Illness in the United States, CDC April 15 2011
  3. What is Salmonellosis? CDC April 5 2012
  4. Davis C, Salmonella Poisoning,
  5. Prevention of Salmonella Enteritidis in Shell Eggs During Production, Storage, and Transportation; Final Rule July 9, 2009, HHS Federal Register / Vol. 74, No. 130 / Thursday, July 9, 2009
  6. Investigation Update: Multistate Outbreak of Human Salmonella Enteritidis Infections Associated with Shell Eggs, CDC December 2, 2010
  7. Salmonella Outbreak Investigations: Timeline for Reporting Cases, CDC August 9, 2010
  8. Egg Safety Final Rule, FDA, July 7, 2009
  9. Advice to Consumers, CDC Aug 26, 2010

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