Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   1 
Guidance on Reducing the Risk of 
Salmonella  Enteritidis in Canadian Shell 
Eggs  
August 2012 
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   2  
TABLE OF CONTENTS  
 
1. Scope ...................................................................................................................... ..................... 3  
2. Definitions ................................................................................................................ .................. 3  
3. Roles and Responsibilities ................................................................................................. ........ 4 
3.1 Government ................................................................................................................ ....................... 4  
3.2 Industry .................................................................................................................. ........................... 4  
3.3 Consumers ................................................................................................................. ........................ 5  
4. Introduction ............................................................................................................... ................. 5  
5. Background ................................................................................................................. ............... 6  
6. Consultation ............................................................................................................... ................ 7  
7. Risk Assessment Overview ................................................................................................... ...... 7 
8. Guidance to Improve the Microbiol ogical Quality of Shell Eggs ............................................ 9  
8.1 Guidance for the Production of Table Eggs ................................................................................. .. 9 
8.1.1 Primary Breeders and Eg g-Type Multiplie r Breeders ....................................................................... ........ 10 
8.1.2 Production of day-old ch icks ............................................................................................ ......................... 10  
8.1.3 Pullet rearing .......................................................................................................... ................................... 11  
8.1.4  S. Enteritidis testing in pu llet and laying  flocks .............................................................................. .......... 11 
8.1.5 Actions to be taken upon finding S. Enteritidis-pos itive flocks ................................................................ 14  
8.1.6 On-Farm Food Safety program recomm endations ............................................................................. ....... 14 
8.1.7 Vaccination  programs .................................................................................................... ........................... 15  
8.2 Guidance when Eggs are Implicated in Human Illness ............................................................... 16  
8.3 Post-Production Guid ance for Table Eggs ...................................................................................  16 
8.3.1 Imported shell eggs des tined for the ta ble market ....................................................................... .............. 17  
8.3.2 Surplus hatching eggs ................................................................................................... ............................ 17  
8.3.3 Table eggs from unre gulated and sm all producers ......................................................................... ........... 18 
8.3.4 Sale of ungraded shell eggs ............................................................................................. .......................... 18  
8.3.5 Sale of cracked eggs .................................................................................................... .............................. 19  
8.3.6 Refrigeration of shell eggs ............................................................................................. ........................... 19  
8.3.7 Egg-grading stations .................................................................................................... .............................. 20  
8.3.8 Processed egg stations .................................................................................................. ............................. 21  
8.4 Education campaigns ....................................................................................................... .............. 22  
9. Implementation ............................................................................................................. ........... 22  
10. References ................................................................................................................ .............. 23  
 
  
 
    
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   3  
1. Scope 
This document is intended to provide guidance to reduce the ri sk of foodborne illness due to 
Salmonella enterica subspecies enterica serovar Enteritidis (hereafter referred to as S. 
Enteritidis) in shell eggs.  The document provides guidance on inte rvention strategies to reduce 
the risk of S. Enteritidis in shell eggs pr oduced by domestic hens ( Gallus gallus ) offered for sale 
on the table market in Canada.  It was devel oped using a health risk assessment approach 
(DeWinter et al. , 2011).  Known limitations in  the ability to identify S. Enteritidis in eggs have 
resulted in controls aimed at reducing S. Enteritidis being put in place at the level of the laying 
flock.  When S. Enteritidis is identified in the environm ent of a laying flock, the eggs from that 
flock are sent to pasteurization for the lifetime of the flock.  Therefore, this document provides 
guidance regarding best practi ces for the egg industry, prov incial/territorial and federal 
governments, primary breeders and egg-type mu ltiplier flocks, and portions of the pullet, 
hatchery and broiler industries th at can affect the presence of S. Enteritidis in the egg industry.  
International evidence also demonstr ates that any control plan for S. Enteritidis in poultry must 
use a top-down approach, that is, one for which the controls begin at the breeding stock that 
supply all of the hens for the egg industry.  Fo r this reason, the guidance document also covers 
the primary breeding stock, the hatchery supply flocks, as well as the hatcheries.  The 
information contained in this document is based on  the current state of scientific evidence and 
developments are ongoing. 
This guidance document represents a consensus-ba sed standard that should be implemented in 
the industry on a voluntary basis wi th the possibility of regulatory backstops in the future, if 
warranted.   
Food safety enforcement bodies at the federal, provincial and territorial level may use this 
guidance document as a reference to assess ad herence of the egg industry to good agricultural 
practices as they relate  to the reduction of S. Enteritidis in shell eggs.  Thus, this guidance may 
be used to assess compliance with  general requirements of  food safety legislation or regulations, 
in particular, compliance with Sections 4 and 7 of the Food and Drugs Act .   
2. Definitions 
For the purpose of this document the following definitions apply. 
 2.1 Broiler flock.   A flock of domestic chickens selec tively bred and reared for their meat. 
2.2 Cracked egg.   An egg with a damaged shell, but w ith an intact membrane, such that the 
egg contents are not leaking. 
2.3 Farm gate.  The premises of the egg producer where the laying flock resides.  
2.4 Flock.   A flock comprises domestic chicke ns housed in an individual barn. 
2.5 Flock testing.  The environmental testing of an egg-type pullet or laying flock to 
determine whether the flock is infected with S. Enteritidis. 
2.6 Laying flock.  A flock of domestic hens during the production of eggs for human 
consumption. 
2.7 Nest Run egg.   A Canada Grade designation under the Canadian Egg Regulations .  Nest 
Run eggs are to be sent to a re gistered processed egg station.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   4 2.8 Pullet flock.  A flock of domestic hens prior to  the period of production of eggs for 
human consumption or for hatching. 
2.9 Regulated flock.  Laying flocks that are regulated by the provinci al egg board and that 
operate under the national supply management system. 
2.10 Shell egg.  A whole, intact egg laid by a domestic hen. 
2.11 Table egg.  A shell egg offered for sale to cons umers (including retail environments, 
restaurants, bakeries, and other foodservice and institutional settings) for the purposes of 
consumption. 
2.12 Test and divert flock management strategy.  Management of a laying flock such that it is 
tested for S. Enteritidis, and if found pos itive, all eggs are diverted to pasteurization for 
the lifetime of the flock. 
2.13 Ungraded egg.  Ungraded eggs comprise shell eggs that have not been graded at a 
federally registered egg station. 
2.14 Unregulated flock.  Unregulated flocks are those with fewer birds than the limits set by 
the provincial egg marketing boards. These limits vary by province and can range from 
99 to 499 birds. 
3. Roles and Responsibilities 
This guidance document, developed as a joint e ffort between Health Ca nada, the Canadian Food 
Inspection Agency (CFIA) and the Public Health  Agency of Canada (PHAC), takes into account 
the roles and responsibilities of industry, government and consumers. 
3.1 Government 
Health Canada has a responsibility for developing  and setting food safety standards that identify 
the nature and assess the level of risk associated with th e consumption of contaminated food 
products and develops guidance documents to help  minimize the risk of foodborne illnesses.  
Health Canada consults and wo rks with the CFIA and provincia l/territorial governments on the 
above to ensure that public health responses are a ppropriate and effective.  It is the role of the 
CFIA and provincial/territorial gov ernments to oversee the food i ndustry to ensure that it meets 
its food safety responsib ilities including the application of  effective and timely management 
strategies appropriate to the ris k, when required.  The role of PHAC  is to promote and protect the 
health of Canadians through l eadership, partnership, innovation and action in public health.  
PHAC has already begun to play a more active role in food surveillan ce across the country, e.g., 
C-EnterNet, a multi-partner program designed to detect changes in trends in human enteric 
disease and in levels of pathogen exposure from  food, animal and water sources in Canada.  In 
addition, the three federal depart ments provide reference laborator y services, conduct food safety 
investigations, Health Risk A ssessment (HRA) and recall actions. 
3.2 Industry 
It is industry's role and responsib ility to comply with all applic able legislative and regulatory 
requirements which include Sections 4 and 7 of the Food and Drugs Act  and to develop and 
implement good manufacturing practices and contro ls that are conducive to the production of 
safe eggs.  Food distributors and retailers are responsible  for controlling the temperature of shell 
eggs during transport and storage to suppress or limit bacterial growth.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   5 3.3 Consumers 
In addition to government agencies and food i ndustries working diligently at minimizing the 
exposure to S. Enteritidis, consumers also have an importa nt role to play in the farm-to-fork 
continuum in adopting safe egg handling and pr eparation practices.  Caterers, parents of young 
children and care providers for the elderly and other vulnerable populations have a higher level 
of responsibility in this regar d.  To this end, Health Canada, the CFIA and the PHAC (and other 
provincial/territorial bodies) deve lop and deliver science-based e ducational material to inform 
consumers and health care providers about the hazards associated with S. Enteritidis in shell eggs 
and how to minimize the risks of foodborne dis ease, with a particular focus on vulnerable 
populations and their families, as well as their care providers. 
4. Introduction 
Salmonella is an important foodborne pathogen worldw ide.  Ingestion of the organism is 
followed by an incubation period, usually eight  to 72 hours, during which the organism 
proliferates in the gut.  Symptoms of salmone llosis range from mild to severe diarrhea, 
abdominal pain and vomiting, as well as fever acc ompanied by headache and chills.  In cases of 
severe diarrhea, dehydration may lead to hypoten sion, cramps, oliguria and uraemia.  The vast 
majority of cases comprise acute illness that la sts a few days, with recovery occurring within a 
week.  Death is uncommon except in the ve ry young, very old, or immunocompromised 
individuals.  Small proportions  of cases develop bacteraemia or meningitis, or may develop 
localised infections causing abs cesses, arthritis, cholecystitis, endocarditis, pericarditis or 
pneumonia.  Long-term sequelae resulting from salmonellosis can include malabsorption of 
essential nutrients (which can result in a co mpromised immune system and may lead to 
infection), allergy, reactive ar thritis, autoimmune disorders and neoplasia.  Although reactive 
arthritis is usually of short dur ation, some patients may develop ch ronic disease and patients with 
certain underlying conditions (for example, haemoglobin abnormalities) may be prone to 
complications. 
Most serotypes of Salmonella contaminate shell eggs on the exterior shell surface, which is 
referred to as horizontal transmission.  The organi sms may gain entry to th e interior contents by 
cracks in the shell or by other ci rcumstances that can lead to e ggshell penetration (for example, 
time and temperature abuse, improper egg washi ng).  Scientifically designed and tested egg 
washing protocols used at egg grading stat ions must comply with Section 9 of the Egg 
Regulations of the Canada Agricultural Products Act.  Egg washing serves to reduce the 
microbial load associated with egg shell surfaces, thereby reducing risk to consumers.  Since the 
early 1990s, eggs have been established as a major vehicle for human cases of  S. Enteritidis 
infections in the internati onal scientific literature.  S. Enteritidis is the key microbial pathogen in 
shell eggs because of trans-ovarian deposition, in other words, vertical transmission of the 
organisms into egg contents as a result of the infected reproductive tis sues of laying hens.  
Laying hens may be infected with S. Enteritidis without showing any signs of illness or disease.  
The problem is exacerbated when contaminated shell eggs are not held under conditions of 
refrigeration, allowing the organisms to access th e nutrient rich yolk and grow rapidly, and by 
consumers’ known preferences for eati ng raw and lightly-cooked eggs.   
There has been an increase in reports of S. Enteritidis outbreaks associ ated with other vehicles 
such as almonds and sprouted seeds.  Reports of S. Enteritidis outbreaks associated with eggs  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   6 may have decreased due to the fact that  eggs are an established vehicle of S. Enteritidis.  
However, eggs will remain an important vehicle of infection due to trans-ovarian transmission 
into intact eggs.  This was demonstr ated by the major 2010 U.S. outbreak of S. Enteritidis due to 
shell eggs with 1,939 known associated illnesse s and in which over 500 million shell eggs were 
recalled (CDC, 2010). 
In Canada, Salmonella has been the second most common en teric bacterial pathogen since at 
least 1997, judging by Salmonella isolates referred to the National Microbiology Laboratory 
(PHAC, 2004) and cases reported through the nati onal notifiable disease program (PHAC, 2009).  
S. Enteritidis consistently ranks among the top th ree serovars associated with human illness in 
Canada since at least 1995, and the top five si nce at least 1983 (PHAC, 2005; Health Canada, 
2003; Khakhria et al., 1997).  Compared to other serovars, S. Enteritidis isolates have increased 
dramatically since 2003 and are now the most prev alent serotype, having re presented 28% of all 
salmonellosis cases in 2005 a nd 23% in 2006 (PHAC, 2007ab).   
5. Background 
S. Enteritidis was noted to be an increasing human health problem through the 1980s, primarily 
in Europe and the United States, and researchers noted that there might be an association with 
infections of the ovaries and oviduc ts in laying flocks (St. Louis et al., 1988; Cowden et al. , 
1989).  Over the next decade , it was established that S. Enteritidis could be deposited in the 
internal contents of an int act shell egg.  The Egg Farmers of Canada (EFC) responded in 1990 
with the launch of its “ Safe from Salmonella” program, which was the first formal program in 
Canada to introduce biosecurity measures to  primary commercial food production (CEMA, 
2002).  EFC also cooperated in an Agriculture and Agri-Food Canada research project to sample 
and inspect laying flocks and eggs to de termine the extent of the problem with S. Enteritidis in 
Canada (Poppe et al., 1991; Poppe et al., 1992).  In 1996, Health Cana da developed an interim 
policy on the issue and the egg indus try began to divert eggs to further processing to inactivate 
the organisms, when S. Enteritidis was identified in the en vironment of a laying flock.  In 1998, 
EFC’s “ Safe from Salmonella” program was modified to incorporate Hazard Analysis Critical 
Control Point (HACCP) principles and renamed Start Clean – Stay CleanTM, and was also 
modified to include free-range, free-run and speci alty flocks such as organic operations.  This 
On-Farm Food Safety program co mpleted technical reviews by the CFIA in 2004 and 2007.  The 
program includes a number of practices intende d to minimize the possibility of introducing 
Salmonella  to a laying flock, as well as on farm insp ections conducted by pr ovincial and federal 
officers that provide each egg producer with a rating and sugg estions for improvement.  Among 
the regulated laying flocks that  operate under the Canadian suppl y management system, EFC has 
been able to achieve ov er 90% participation in Start Clean – Stay CleanTM, and 100% of egg 
producers are currently being tested for S. Enteritidis.  Currently, the program is phasing in an 
insurance program (the Canadian Egg Industr y Reciprocal Alliance) that may provide 
compensation when egg producers are faced with S. Enteritidis-infected flocks. 
Most of the table egg sector in  Canada is regulated by the Egg Farmers of Canada and the egg 
marketing boards in the 10 provinces and the territories. Together they administer the 
production, pricing, marketing and promotion of eggs in Canada. Based upon egg production 
statistics for 2006 (Statistics Canada, 2007), eggs from regulated flocks account for 
approximately 97% of eggs on the table market.  This estimate takes into account an estimate for 
table eggs from unregulated flocks  based on Census of Agriculture  data (Statistics Canada, 2007)  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   7 and EFC data for imported table eggs (CEMA, 2007) . However, hatching eggs that proceed to 
the table market, sales at the farm gate, and sale s at farmers’ markets are not accounted for in the 
estimate and therefore the estimate may be higher than the true value.  The Canada Agricultural 
Products Act is the authority for the Egg Regulations , which specify certain requirements for 
eggs that relate to food safety.  Eggs must be  graded at federally-regi stered grading stations, 
which must meet requirements, including temperatur e and humidity controls for storage of eggs, 
and other hygienic requirements. During the grad ing process, cracked eggs only meet the grade 
Canada C, and thus are sent fo r pasteurization.  Dirty eggs do not  meet any Canada grade; they 
are considered unfit for human consumption.  Gr ading stations are monitored regularly by the 
CFIA, and twice per year undergo environmen tal sampling for salmonellae. Positives are 
serotyped and corrective actions ar e required.  Most of the provinces  and territories refer to the 
Canadian Egg Regulations  as the authority for table eggs in their jurisdiction. 
One noteworthy consideration is th at grade A table eggs in Canada can originate from a number 
of sources, not just from regulated flocks.  In gene ral, there is very limite d data about these other 
sources of eggs includin g their proportion of market share, flock management and egg storage 
and handling practices where th ey relate to the risk of S. Enteritidis, and the proportion of 
illnesses attributed to eggs from these sources .   Therefore, although this guidance document 
mainly addresses recommendations for table eggs from regulated flocks, it also makes 
recommendations recognizing that the additional s ources of eggs reaching the table market also 
represent a potential risk to consumers.  Th e coverage of the On-Farm Food Safety programs 
(including environmental testing for S. Enteritidis), monitored and controlled egg storage and 
handling practices, carefully controlled egg wash ing practices, and governmental surveillance 
and monitoring programs in pl ace to reduce the risk of S. Enteritidis in grade A table eggs, do not 
necessarily extend to eggs origin ating from other sources and th erefore sources of table eggs 
outside of the regulated flocks may repr esent an increased risk to consumers. 
6. Consultation 
This document has been prepared by experts from  Health Canada, CFIA, and the Public Health 
Agency of Canada (PHAC).  Input has been soug ht from key industry st akeholders including the 
Egg Farmers of Canada (EFC), the Canadian Hatching Egg Producers (CHE P), and the Canadian 
Poultry and Egg Processor’s Council (CPEPC) during the developmen t of this guidance 
document, and was given full consid eration in the development of this guidance.  Furthermore, 
Health Canada hosted a public consultation to gather opinions from the public, veterinary 
professionals, agriculture profe ssionals, health professionals, people in the food industry, and 
others who might be affected by the guidan ce document. The input received from the 
consultation period was given full consider ation and the guidance document underwent 
significant revision. A report from the public co nsultation will be posted on Health Canada's 
Web site and was also emailed to all participants. 
7. Risk Assessment Overview 
A risk assessment entitled “Risk Assessment of  Shell Eggs Internally Contaminated with 
Salmonella  Enteritidis” was published by Hea lth Canada in 2011 (DeWinter  et al. , 2011).  The 
development of the risk assessment involved an  extensive literature review, as well as 
consultation with experts from the CFIA and PHAC.  Interested parties are invited to consult the  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   8 risk assessment for additional details or informa tion, as it contains an ex tensive review of many 
aspects related to S. Enteritidis that are not covere d in this guidance document;. 
The risk assessment highlighted the fact that  eggs are consumed by every segment of the 
Canadian population.   Egg consumption in 2005 was 15.6 dozen per person per year (Agriculture 
and Agri-Food Canada, 2006).  Since 1995, per capit a processed egg consumption has increased 
by 30% (Agriculture and Agri-Food Canada, 2006).   In 2005, the total pro duction of eggs for 
human consumption in Canada was approximately  6.3 billion, of which approximately 75% were 
sold as table eggs (Agriculture and Agri-Food Canada, 2006).  The remaining eggs are sent to 
processed egg stations to be pasteurized fo r use in processed egg products. Normal and 
susceptible populations consume an average of 7 4.7% and 79.0% of shell eggs, respectively, in a 
home setting, with the balance of consumption o ccurring in a food service and institutional (FSI) 
setting.  In total, normal and susceptible populations consume an average of 0.14, 12.7, and 
87.2% of raw, lightly cooked, and well-cooked egg meals in home settings, and 0.11, 13.7, and 
86.2% in FSI settings.  Susceptible populations  consume an average of 0.25, 12.8, and 87.0% of 
raw, lightly cooked, and well cooked egg meal s in home settings, and 0.04, 11.0, and 89.0% in 
FSI settings.  
Due to data limitations, the scope of the risk asse ssment comprised internally contaminated eggs 
produced by the regulated laying flocks pa rticipating in environmental testing for S. Enteritidis in 
the years 2005 and 2006.  Therefore, the risks of illness from S. Enteritidis due to externally 
contaminated eggs, cracked eggs, dirty eggs, imported eggs, eggs from unregulated producers 
(farm gate, farmers markets), hatchery surplus eggs (layer- and broile r-breeders), and ungraded 
eggs were not included in the risk assessment.   
The results of the risk assessment demonstrated  that an average of approximately 5 per 1000 
regulated laying flocks were infected per year.  The dist ribution of the prevalence of 
contaminated eggs yielded an average of 1.7 per million eggs from the regulated laying flocks.  
The results also demonstrated that consumers are 2.7 times more likely to become ill from 
consumption of eggs in a FSI setting than in a home setting.  Susceptible  individuals are 1.4 to 
1.5 times more likely to become ill from consump tion of a serving from a contaminated egg than 
normal individuals. Illnesses were found to be disproportionate to expos ures, with the poorest 
storage and handling conditions representing only 0.6% of exposures but resulting in 46% of 
illnesses, whereas ideal storage and handling conditions accounted for 96% of exposures, but 
49% of illnesses.  These findings suggested th at risk management options targeting both 
contaminated egg prevalence and the number of illnesses that result from an S. Enteritidis-
contaminated egg would be appropriate.   
Simulations of risk management strategies were  performed as an important component of the 
risk assessment – to inform development of the guidance document.  Simulated risk management 
strategies were examined with the purpose of reducing the prevalence of contaminated eggs and 
the number of illnesses per contaminated e gg.  The following observations were noted:  
 Full vaccination of all laying flocks would reduce the number of illnesses to 4% of baseline 
(no vaccination) levels. Target ed vaccination (in other words, when the previously housed 
flock tested positive) would result in approximately the same reductions. 
 A test and divert flock management strategy in  which all laying flocks’ environments were 
tested for the presence of S. Enteritidis at the beginning of the laying cycle and 8-10 weeks 
before the end of lay, with di version of eggs from flocks  found to be occupying positive  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   9 environments, would reduce the number of illnesses to between 2% and 29% of baseline 
levels, depending upon whether the majority of in fections occurred prior to the laying cycle 
or during the laying cy cle, respectively.   
 Replacing all pooled eggs in FSI settings with  pasteurized egg products would decrease the 
number of illnesses to 29% of baseline (no substitution with pasteurized products).   
 A 50% reduction in the consumption of raw or  lightly cooked egg meals or recipes would 
decrease illnesses to 92% (FSI settings) and 72% (home settings) of baseline.   
 Improving egg storage and handling conditions such that yolk membrane breakdown and 
growth of S. Enteritidis never occurred, would decrease  the number of illnesses to 24% (FSI 
settings) and 56% (home se ttings) of baseline.   
8. Guidance to Improve the Microbiological Quality of Shell Eggs 
Health Canada’s goal is to protect the health of Canadian consumers by reducing the prevalence 
of shell eggs internally contaminated with S. Enteritidis offered for sale  on the table market and 
to reduce the number of illnesses resulting fr om an internally contaminated egg.   
This guidance document outlines Health Canada’s position on the microbiological safety of shell 
eggs with regards to S. Enteritidis. Due to the vertical transmission of the organism by the 
transovarian route, control measures that will ensu re the microbiological safety of shell eggs with 
respect to S. Enteritidis will be most effec tive if they were to occur along the entire supply chain 
of the egg industry, from the gra ndparent flocks through to the time the egg is offered for sale to 
the consumer. Current flock prevalence data from the regulated laying flocks indicates that the 
prevalence of S. Enteritidis among regulated laying flocks is low, suggesting that current control 
programs should be continued. This has also influenced the types of simulated risk management 
options that were explored to improve curren t control programs. This guidance document also 
makes recommendations to address the risk of S. Enteritidis from other sources of grade A table 
eggs which may represent a source of  increased risk to consumers.  
8.1 Guidance for the Production of Table Eggs  
Reducing illnesses due to the consumption of eggs internally contaminated with S. Enteritidis 
can be accomplished by reducing the prevalence of contaminated eggs, and/or by reducing the 
number of illnesses per contaminated egg. Floc k prevalence and contaminated egg prevalence 
within a positive flock have a direct effect on the number of illnesses from consumption of shell 
eggs, such that decreasing S. Enteritidis prevalence by a specified percentage results in an 
equivalent percentage decrease in the mean number of human illnesses (DeWinter et al. , 2011).   
Preventing S. Enteritidis infection of laying flocks requires application of S. Enteritidis testing 
and/or control measures from the breeding floc ks through to the laying flocks themselves.  
Timely sharing of data related to S. Enteritidis testing results between appropriate provincial and 
federal government and industry stakeholders  is critical to the success of reducing S. Enteritidis 
in the industry. Testing programs have the adde d benefit of providing in formation as to the 
importance of various sources of S. Enteritidis infection, so that  future HACCP-based control 
programs can be modified to adequa tely control for these sources.   
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   10 8.1.1 Primary Breeders and Egg-Type Multiplier Breeders 
In any S. Enteritidis control program, it is internationally recognized that the most effective 
control can be applied using a top-down approach within the production scheme (Wray, Davies, 
and Evans, 1999).  In Canada, the primary breede rs are not considered to be a source of S. 
Enteritidis as these flocks are monitored for Salmonella  every 3 weeks and are required to be SE-
free. This also allows the primary breeders to me et the EU Export Protocol.  The test results are 
shared with and monitored by the CFIA.  Under an industry-led insurance program, the egg-type 
multiplier breeders are also required to be free of S. Enteritidis. 
8.1.2 Production of day-old chicks 
Due to an industry-led program that comprise s testing and control m easures, the egg-type 
hatchery supply flocks (including the primary br eeders and egg-type multi plier breeders) for the 
layer industry have rarely been  identified as a source of S. Enteritidis over the past 15 years 
(Boucher, 2008; Cereno, 2012).  However, this is  not the case for the br oiler sector and this 
source of S. Enteritidis could resu lt in cross-contamination at hatc heries producing both egg-type 
and meat-type chicks, as well as at other st ages where broiler opera tions may overlap egg 
operations (for example , common equipment or catching crews).  It has been brought to Health 
Canada’s attention that an investiga tion of human illnesses and outbreaks of S. Enteritidis from 
eggs pointed to regulated laying fl ocks that were infected with S. Enteritidis due to the numerous 
overlaps with the broiler sector.   
The CFIA currently performs flu ff testing every six weeks in ha tcheries for the detection of 
salmonellae.  Day-old chicks are highly susceptible to S. Enteritidis infection; it follows that 
preventing exposure at this  age is critical.   
 
Recommendation #1 
Egg-type and meat-type chicken hatchery supply flocks should be free of S. 
Enteritidis.  Hatcheries should source ha tching eggs only from hatchery supply 
flocks that are free of S. Enteritidis.  
 
Layer hatchery supply flocks are already close to meeting this recommendation. Broiler hatchery 
supply flocks may need more time to work towards this recommendation.   
 
Recommendation #2 
Egg-type chicks should not be raised to be or supplied as egg layers, where likely 
exposure to S. Enteritidis has taken place.  
 
Current protocols require notification of positive fluff test results to the industry stakeholder and 
the appropriate provincial egg board, who then decides upon the c ourse of action.  In addition, 
the CFIA should perform additional testing at the hatchery and the hatchery supply flock level to 
determine the source of S. Enteritidis.  Exposure of  egg-type chicks to S. Enteritidis should be  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   11 assessed using bacteriological monitoring programs, together with consider ation of the protocols 
in use at the hatchery.         
8.1.3 Pullet rearing  
 
Recommendation #3 
Pullets should be reared using appropri ate farm management and biosecurity 
practices to achieve sufficient separation from broiler operations as well as other 
poultry and other livestock operations, so as to prevent cross-contamination.    
 
Producers should consult with  the appropriate provincia l or federal government 
recommendations (for example , CFIA, Ontario Ministry of Agricu lture, Food, and Rural Affairs) 
for additional information regarding poultry biosecurity, which should also provide a sufficiently separated environment for pullet production.   
Measures for rearing S. Enteritidis-free pullets will likely be  found to be similar to the HACCP-
based control measures for laying flocks, such as providing feed and water free of S. Enteritidis, 
rodent control, all-in all-out  flock management practices, as  well as effective cleaning and 
disinfection between flocks and effective biosecurity.     
8.1.4 S. Enteritidis testing in pullet and laying flocks 
 
Recommendation #4 
Pullets should be tested for S. Enteritidis at least once during the pullet-rearing 
stage.  Laying flocks that are supplying sh ell eggs for the table market should be 
tested for S. Enteritidis a minimum of twi ce per laying cycle.     
 
Chickens can be infected through horizontal or  vertical transmission, so testing should be 
practiced in order to detect bot h sources of infection.  Test re sults should be provided to the 
CFIA to enable ongoing monito ring of trends related to S. Enteritidis, which will allow 
appropriate and effective use of program resources .  Testing can also provide verification of the 
efficacy of On-Farm Food Safety programs in reducing the prevalence of Salmonella  in laying 
flocks. 
Laying flocks should be tested for S. Enteritidis by performing envi ronmental sampling, which is 
in line with current practices among regulated floc ks and the scientific literature (Davies and 
Breslin, 2001; EFSA, 2010; Kinde et al., 2005).  Currently, flock tes ting schemes are in place in 
all provinces, as specified by the provincial government or the provincial egg board, but many 
aspects of the sampling and methodology differ.  The minimum standard appears to be that 
flocks are tested once during the laying cycle, ap proximately 8 to 10 weeks before the end of the 
laying cycle.  Although the timing of this test pr ovides information about the environment that 
the subsequent flock will occupy, it does not prov ide risk mitigation for th e initial 42 to 44 weeks 
of egg production by that flock.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   12 Pullets  Testing should ensure that pullets are free of S. Enteritidis infection before transport to 
laying facilities.  Due to the increased suscep tibility of young birds, pul let testing should be 
performed early during the pullet growing stage to  ensure that pullets being raised are not 
infected.  The test results should be received in time to ensure that pullets are free of S. 
Enteritidis prior to shipment to a laying facility , and documentation of the results of testing can 
be provided to (and may be requi red by) the egg producer.     
Laying flocks  In 1989, Humphrey demonstr ated that naturally S. Enteritidis-infected laying hens 
tended to produce contaminated eggs intermittently, but at the same time by different hens in a 
flock.  Since that study, other rese archers have demonstrated that salmonellae are more likely to 
be isolated from infected birds or their envi ronments during a period of stress (Holt, 1993; 
Nakamura et al. , 1994).  It is therefore thought that the in creased production of contaminated 
eggs correlates with the degr ee of cecal carriage and increased fecal shedding (Davies and 
Breslin, 2001).  Similarly, subclinic al infections in hens may be  exacerbated during periods of 
stress, resulting in increased shedding  and an increased ability to detect S. Enteritidis in the 
environment.  Therefore, testing at known times of stre ss would be expected to be more efficient 
at detecting infected flocks.  K nown sources of stress (not all of which are relevant to Canadian 
egg production) include induced molt, withdrawal of  feed and water, temp erature (too hot or too 
cold), introduction of new bird s to a flock, handling and/or fr ight, disease and peak of lay.   
The Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella  
Enteritidis  demonstrated that the number of illnesses due to S. Enteritidis in shell eggs would be 
expected to decrease as the numbe r of times a flock is tested increases, and as environmental test 
sensitivity increases (DeWinter et al. , 2011).  Depending upon the relative importance of vertical 
and horizontal transmission of S. Enteritidis, two tests during th e approximately 52 week laying 
cycle of all regulated flocks, plus diversion of eggs to further processi ng, would be expected to 
achieve a 71 to 98% reduction in contaminated egg prevalence.   
The recommended minimum testing for laying flocks  comprises two tests, with the first test 
occurring between receipt at the laying facility  and the peak of lay (between approximately 19 
and 26 weeks of age).  This is a period of tim e when the birds are physio logically stressed, and 
testing will effectively detect infected flocks.  The timing of this test will also mitigate the risk of 
contaminated eggs produced from flocks infect ed early in the laying cycle.  The second test 
should occur when the laying flock is between 36 and 60 weeks of age.   
Testing protocols in use as of 2005-2006 (used in the risk assessment) dictate a minimum of one 
test, which generally occurred 8-10 weeks before the end of lay (corresp onding to a flock age of 
62 to 64 weeks of age).  Testing 8-10 weeks before  the end of lay has the advantage of increased 
test efficacy due to increased physio logical stress of the laying floc k as they approach the end of 
lay, and confidence that the subsequent flock is  being placed into a clean environment.  
However, it also has the disadvantage that the recei pt of test results usua lly occurs after the end 
of the laying cycle, thereby not permitting the dive rsion of eggs away from the table market.  For 
this reason, it will also be acceptable for the second test to occur earlier in the laying cycle (when 
the flock is between 46 and 64 weeks of age) because this has the advantage of permitting the diversion of eggs from positive flocks, although th ere may be an associated decrease in test 
efficacy since the flocks are not likely to be experiencing stress at this time.  The 
recommendations for the timing of testing allow 18 weeks of flexibility in the timing of the 
second test, but also incorporate a minimum of 20 weeks between th e two tests so that the tests 
are fairly well-distributed over the 52 week laying cycle.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   13  
Recommendation #5 
The practice of induced molting of laying  flocks by feed withdrawal should be 
discontinued.  Any molted laying floc ks should undergo increased testing for S. 
Enteritidis. 
 
Although molting is rarely practic ed in Canada, flocks that are molted experience increased 
stress. Molting induced by feed withdrawal has been associated with an increased rate of 
infection with salmonellae (Garber et al., 2003; Holt, 2003; Castellan et al., 2004; Gast, 2007; 
Golden et al., 2008).  The increased S. Enteritidis prevalence among these flocks may also be 
associated with increasing environmental contam ination in continuously occupied houses (Wales 
et al., 2007).  Post-molt laying flocks should be tested  every 3 months, with the first test for the 
post-molt flock occurring before the fl ock begins its next lay cycle.   
The literature is not conclusive as to whether induced molting using alternative methods results 
in an increased rate of infection with Salmonella (Callaway et al., 2009; Donalson et al., 2008; 
Gutierrez et al., 2008; Murase et al. , 2006). 
 
Recommendation #6 
For laying flock environmental testing for S. Enteritidis, all provinces and 
territories should follow at least the mini mum national standard sampling protocol 
and methodology.  Sampling in the flock envi ronment should comprise a variety of 
samples. 
 
Currently, egg producers with regulated laying fl ocks supplying eggs for the table egg market 
must perform environmental testing for S. Enteritidis (EFC, 2012).  The minimum 
microbiological sampling protoc ol for environmental testi ng specifies the following: 
 Mandatory S. Enteritidis environmenta l testing of laying flock at least twice during the 
laying cycle; 
 sampling carried out by qualified staff of the provincial or te rritorial egg board; 
 ≥ 60 sites sampled per flock; 
 focus on sampling dust and egg conveyances  (swabs, dust, fluff, scrapings); 
 additional sampling of rodent droppin gs and dead insects, if found; 
 a minimum of 4 composited samples should be tested (that is, the samples from up to 15 
separate sites may be composited); and 
 the testing must be performed by an accredite d laboratory using a cultural method for the 
isolation of Salmonella spp. approved by the Chief Veterinary Officer of each province. 
  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   14 The use of a minimum sampling protocol and methodology helps to ensure consistency in 
consumer safety and makes data comparisons po ssible.  The determination of which sampling 
protocols and methodologie s will form the basis of the test ing program should be based on best 
practices, determined by a working group comprised of appropriate stakehol ders including EFC, 
provincial egg boards, poultry vete rinarian experts, the CFIA, a nd Health Canada.  Sampling in 
the flock environment should comprise a variety of  samples, such as dust samples from sources 
near the birds or from ventilation fans, e gg belts, egg conveyances, egg spillage from 
conveyances, and/or the nest floor for nest systems, feces, manure, or litter, as well as vectors 
such as flies and rodents or their droppings.  Du st samples should be emphasized in the sampling 
plan as they have been shown to  be an important reservoir of Salmonella  spp. (Kinde et al., 
2005; Wales et al, 2006; Gast, 2007).  Samples from agricult ural environments are expected to 
have a higher load of backgr ound microbiota, including other Salmonella serovars.  Therefore, a 
cultural method that permits sufficient resuscita tion and has sufficient selectivity must be used 
for isolation. Methods intended for food and f ood manufacturing envir onments should not be 
used without sufficient validation.   
8.1.5 Actions to be taken upon finding S. Enteritidis-positive flocks 
 
Recommendation #7 
When the environment of a layi ng flock tests positive for S. Enteritidis, the eggs 
from that flock should be diverted for fu rther processing, for the lifetime of that 
flock. 
 
After depopulation, cleaning and disinfection, the environment should be retested and not 
contain any salmonellae prior to repopulation wi th the subsequent flock. Furthermore, an 
investigation should be pursued by the provincia l egg board or EFC to review biosecurity 
measures and suggest on-farm improvements as corrective actions.  Wher e investigations are 
performed, the data collected re garding the poten tial sources of S. Enteritidis contamination can 
be used to improve the On-F arm Food Safety program.   
 
Recommendation #8 
Pullet flocks that test positive for S. Enteritidis should not be supplied to egg 
producers for use as laying hens. 
 
8.1.6 On-Farm Food Safety program recommendations 
 
Recommendation #9 
Laying flocks that are supplying shell eggs for the table market sh ould participate in 
a HACCP-based On-Farm Food Safety program designed to reduce S. Enteritidis,  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   15 and to address multiple potential sources of S. Enteritidis. 
 
On-Farm Food Safety programs for the egg industry should be reviewed periodically to ensure 
that all possible sources of S. Enteritidis are accounted for as new information and data become 
available.  Specific attention s hould be given to the following: 
 Poultry feed 
 Sources of possible cross-contamination su ch as equipment, personnel and vectors 
 Biosecurity practices between di fferent operations (for example , layer or pullet flocks and 
broiler flocks on the same or different premises) 
Internationally, Salmonella has been recognized as a hazard in animal feed, potentially serving as 
an important vector for the introduction to a farm (Crump et al. , 2002; EFSA 2008; Davies and 
Wales, 2010).  In a Canadian study, S. Enteritidis was found in 2% (2 of 111) of finished pelleted 
poultry feed samples (Bucher et al. , 2007), suggesting that feed may represent a source of 
exposure.  Producers may wish to select feed fo r laying hens, pullets, and egg-type chicks that 
has undergone a treatment (for example , heat treatment) that has b een verified to inactivate S. 
Enteritidis. Egg producers mixing feed on-farm shoul d have their feed and/or feed ingredients 
tested regularly for S. Enteritidis. 
8.1.7 Vaccination programs  
 
Recommendation #10 
Laying flocks that are moving into  houses that tested positive for S. Enteritidis while 
being inhabited by the previous layi ng flock, should be vaccinated. 
 
The relative prevalence of S. Enteritidis in vaccinated versus unvaccinated flocks has not been 
reported, but based on a 2004 study by Davies and Breslin, the average prevalence of positive 
eggs from positive non-vaccinated flocks is 25 times that in S. Enteritidis-positive vaccinated 
flocks.  Vaccination of all regulated laying floc ks was simulated to reduce contaminated egg 
prevalence by 96% in a risk assessment that ev aluated the simulated effects of several risk 
management options on the prevalence of S. Enteritidis-contaminated eggs (DeWinter et al. , 
2011).   
Veterinary vaccines are licensed by the Canadian Ce ntre for Veterinary Biologics of the CFIA.  
To meet the licensing requirements, each product mu st be shown to be pure, potent, safe, and 
effective when used as recommended in the targ et species according to the label claim.  To 
conform to these requirements, salmonellosis vaccines are tested in vaccination-challenge 
experiments where groups of vaccinated bird s and unvaccinated controls are exposed to S. 
Enteritidis, and monitored for evidence of infecti on and contamination of organs, tissues, faeces 
and eggs.  Supplemental field efficacy studies may also be conducted to evaluate the benefits of 
vaccinating birds on S. Enteritidis -infected premises.  The list of currently licensed veterinary 
vaccines for S. Enteritidis can be accessed on th e CFIA’s website (CFIA, 2012).  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   16 Vaccination should never be used as a substitute  for cleaning and disinf ection between flocks.  
Gast (2007) reported that neither inactivated nor live attenuated Salmonella vaccines have 
consistently prevented infection in layers, especially against high dose challenges.  Vaccinating 
an incoming flock decreases the likelihood of a flock becoming infected, and has also been 
shown to decrease the rate of produc tion of contaminated eggs, should a flock become infected.     
A vaccinated flock would still be subject to S. Enteritidis testing (as per 8.1.4), and the same 
actions would be taken in the event of a positive result.   
As an alternative to vacc ination, the use of probiotic s as a means of reducing Salmonella spp. 
infections may be considered in the future. Prob iotics administered to chicks might prevent or 
decrease colonization of laying hens by S. Enteritidis, by extension re sulting in a decrease in 
contaminated egg prevalence. However, a prerequisi te for this would be the approval of probiotic 
products for such usage, by the Veterinary  Drugs Directorate of Health Canada. 
8.2 Guidance when Eggs are Impl icated in Human Illness 
The Public Health Agency of Canada uses a va riety of tools, such as the National Enteric 
Disease Surveillance Program and PulseNet Canada, to perform surveillance and investigate clusters or outbreaks of human illnesse s.  When eggs are implicated in S. Enteritidis illness and 
confirmed either epidemiologically  or by isolation of the organi sm from the implicated food, a 
follow-up investigation is normally undertaken by the CFIA to determine the source of the eggs.  
When the originating flock is identified, it s hould undergo bacteriolo gical examination for S. 
Enteritidis.  Eggs from a positive flock or epid emiologically linked to salmonellosis should not 
be allowed for sale as table eggs, but should be  sent to a processed egg station for further 
processing (see 8.3.8).  If eggs from a positive floc k are being sold at re tail, a health risk 
assessment should be requested from Health Canada  to determine the health risk level and any 
subsequent intervention measures  to address the risk.    
8.3 Post-Production Guidance for Table Eggs 
Additional recommendations for the safe producti on of eggs encompass a variety of issues 
related to the origin  of the table eggs or to the handling of  eggs from the point of lay through to 
the point of sale.  These recommendations do no t stem directly from the risk assessment. 
Any egg producer, regardless of size, may put cons umers at risk by supplying eggs for the table 
market from a flock infected with S. Enteritidis (whether knowingly or not).  In addition, eggs 
that are not stored or handled in a way that minimizes the S. Enteritidis hazard may put 
consumers at risk. The following two outbreak i nvestigations provide evidence supporting the 
hypothesis that table eggs originating from sources  outside the regulated se ctor may represent an 
increased public health risk.  
Taylor and colleagues (2012) inve stigated an increase in the ra te of human infections with S. 
Enteritidis in British Columbia between 2007 and 2010 and identified eggs as the most likely 
source of illness; eggs were consumed both inside  and outside the home, and the majority of the 
clusters were associated with  the use of ungraded eggs in foodservice establishments.  
In Alberta in late 2010, there was an outbreak of S. Enteritidis involving at  least 91 known cases 
that resulted in guilty pleas fo r 15 charges filed under the Public Health Act in the Alberta 
provincial court against a foodser vice establishment (Slade, 2012) .  The outbreak was linked to 
the repeated sale of ungraded and dirty eggs to a foodservice establis hment, with poor food  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   17 handling practices and a lack of refrigeration of the eggs cited as additional contributing factors 
(Everett, 2012). During the investig ation, it was revealed that the sale of dirty ungraded eggs by 
the same individual had resulted in a firs t conviction in September 2002, with multiple 
subsequent convictions and fine s leading up to the outbreak of  2010. The individual has been 
jailed twice for contempt of court for refusing to  “stop selling filthy, low-grade eggs on Calgary 
street corners despite re peatedly being ordered to stop” (Cormier, 2012). In other provinces and 
territories, the source and quality of eggs is not captured du ring public health i nvestigations, and 
therefore, it would not be possible to identify factors that contributed to illness when eggs are 
linked to human S. Enteritidis illnesses. This would be es pecially true in those provinces and 
territories that also permit th e sales of cracked and/or ungrad ed eggs to consumers.   
The goal is to achieve a high level of consumer  safety by recommending measures to equalize 
the microbiological risks associated with different sources of eggs. 
8.3.1 Imported shell eggs destin ed for the table market 
 
Recommendation #11 
Imported shell eggs should only be sou rced from foreign exporters who can certify 
that eggs originate from laying hens  under an equivalent testing scheme for S. 
Enteritidis, with environmental test results consistently being negative for S. 
Enteritidis. 
 
Imported shell eggs for the table market should meet the same requirements as Canadian table 
eggs.  The aim is to ensure an equivalent level of protection for both domestic and imported 
products.   
 
Recommendation #12 
The importation process for shell eggs (for both global  and supplemental import 
permits) should allow effective tracef orward and traceback investigations. 
 
It is anticipated that the implementation of th e recommendations in this guidance document will 
result in standardized requirements for domestic table eggs in Canada, which will in turn permit 
a harmonization of requirements for table eggs that may also be applied to imported table eggs.   
8.3.2 Surplus hatching eggs 
 
Recommendation #13 
Surplus hatching eggs that are re-routed for human consumption should proceed to 
processed egg stations for pasteurization. 
  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   18 Section 4(e) of the Egg Regulations  states that eggs that have b een in an incubator cannot be 
graded.  Therefore, surplus hatching eggs that  have undergone any portion of the setting or 
incubation process cannot meet any Canadian grade for shell eggs.   
Surplus hatching eggs proceeding to pasteurization should also meet other applicable food safety 
requirements established for laying flocks (for example, veterinary drugs).   
8.3.3 Table eggs from unregulated and small producers 
 
Recommendation #14 
Shell eggs being offered for sale at retail a nd to foodservice and institutional settings 
should be graded, and should originat e from laying hens under a HACCP-based 
control program with at a minimum, an equivalent testing scheme for S. Enteritidis, 
with all environmental test result s consistently being negative for S. Enteritidis. 
 
Table eggs from flocks that are not operat ing under HACCP-based pr inciples and are not 
following a test and divert program for S. Enteritidis, pose a higher risk of salmonellosis for the 
consumer.  All laying flocks th at are producing eggs for the ta ble market, regardless of size, 
including grandfathered flocks and speciali zed flocks, should operate under HACCP-based 
principles including an environmental testing and egg diversion program for S. Enteritidis (8.1.4 
and 8.1.5).  Table eggs from unregulated flocks not complying with the recommendations in this 
guidance document should not be supplied for the ta ble market, but should be diverted for further 
processing.     
8.3.4 Sale of ungraded shell eggs 
 
Recommendation #15 
Only graded eggs should be permi tted for sale at farmers’ markets. 
 
The absence of grading requirement s, standards, and inspections fo r shell eggs, together with the 
absence of programs addressing food safety c oncerns among egg producers, will result in a 
greater likelihood of the internal and extern al contamination of ungraded eggs with Salmonella  
spp. and S. Enteritidis.  Sales of ungraded eggs at farm ers’ markets may further increase the risk 
of contamination due to issues with traceabil ity, storage times and temperatures, and egg 
washing practices.  Eggs offered for sale at farm ers’ markets have been known to be mixed from 
different sources or placed into reused egg cartons and offered for sale by third parties.  In the 
event of illness, a traceback investigation may iden tify a farmers’ market, but may not be able to 
identify the flock of origin, pr eventing public health action.  Reuse of egg cartons may lead to 
external shell contamination.  Fu rthermore, the storage conditi ons of eggs during transit and 
sales at farmers’ markets have been know n to exceed refrigeration temperatures.   
Ungraded eggs from small farms may not be fr esher or more locally-produced compared to 
graded eggs from large egg farms.  Across Cana da, there are currently 103  very small federally  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   19 registered grading stations in operation that grade less than 7 50 dozen eggs per week (Scaife, 
2011).  The eggs from these very small grading stations are produced, graded, and sold locally. 
Graded eggs are packaged with a best-before-date  and usually arrive at the store within 4 to 7 
days of being laid (EFC, 2009), wh ereas the age of ungraded eggs may not be established at the 
point of sale.  Furthermore, since ungraded eggs  are not required to have  packaging indicating a 
best-before-date, they may be st ored for greater periods of time  in the homes of consumers.  
The process of grading eggs need not be cost prohibitive for small egg farmers. The minimum 
requirements for establishment of a small grading f acility can be as simple as a dedicated room, 
potable water, and some basic equipment (e.g., fri dge, sink, egg scale, candling light), and should 
be affordable for most egg producers wishing to sell their shell eggs to restaurants, FSIs, or in a 
retail environment (Scaife, 2009).  Small producers are encouraged to cont act their local CFIA 
office for a discussion of their n eeds with respect to grading.   
8.3.5 Sale of cracked eggs 
 
Recommendation #16 
Cracked eggs should not be offered for sale as table eggs.  Cracked eggs should only 
be sold to: 
a) federally-licensed processing stations for pasteurization, or   
b) food processing plants operating und er Good Manufacturing Practices, with 
the condition that the egg ingredients receive a heat treatment equivalent to 
pasteurization (in other words, validat ed for a minimum 5-log reduction of S. 
Enteritidis). 
 
Cracked shells permit the penetratio n of all salmonellae into eggs a nd are thus more likely to be 
contaminated with S. Enteritidis or other salmonellae.  The sale of cracked eggs on the table 
market poses an increased risk to consumers.   Health Canada’s long-term position has been that 
cracked eggs should not be offered fo r sale as table eggs.  This is also an internationally accepted 
hygiene standard for eggs (Codex Alimentarius Commission, 2007).   
8.3.6 Refrigeration of shell eggs 
 
Recommendation #17 
All sectors involved in the production or handling of shell eggs  should ensure that 
their processes respect the prompt refrigera tion of eggs, in order to maintain the 
microbiological quality of eggs. 
 
A recent study has shown that as little as 12 hours at 30°C permitted S. Enteritidis penetration 
from the vitelline membrane into th e yolk in 11.5% of eggs inoculated in vitro (Gast et al. , 
2008).    
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   20 On-farm: 
At the farm level, producers should attempt to co llect eggs as frequently  as possible, ideally a 
minimum of twice per day, and transport them to cooled storage or a grading station in a timely 
fashion in order to decrease th e length of time at which eggs ar e held at temperatures above 
refrigeration. Where on-farm holding is necessa ry, the microbiological quality of the ungraded 
eggs should be maintained by holding between 10 °C and 13°C with 70 to 85% relative humidity, 
to prevent cracking and sweating. It should be noted  that the goal is to slowly decrease the 
temperature of eggs, because too-rapid a cooling process can result in negative pressure in the 
egg causing contraction of the cont ents, resulting in external shell contaminants being drawn into 
the egg (Gast, 2005).  Trucks used to transport eggs should be capable of continuing the slow 
cooling process, or in cases wh ere the duration of tran sit is short (that is , less than two hours), 
that the temperature of the eggs cannot increase. 
Grading: 
The Canadian Egg Regulations specify the holding temperatures of eggs at registered grading 
stations. Ungraded eggs, Nest Run eggs, and eggs bearing a dye mark are to be held at no more 
than 13°C, while eggs graded Canada A, Canada B, or Canada C are to be stored at no more than 
10°C (as per an amendment in force as of Sept ember, 2008). Trucks used to transport eggs 
should be capable of maintaining the eggs in a refrigerated state.   
Post-grading: 
As the shell eggs proceed through grading sta tions and into retail settings, the storage 
temperature continues to be reduced further to he lp preserve the quality and safety of the eggs. 
When eggs reach retail, they should be handled as  a perishable food to be kept refrigerated. This 
is under municipal jurisdiction and usually re quires refrigeration at 4°C or less.   
8.3.7 Egg-grading stations 
 
Recommendation #18 
Egg-grading stations should include in th eir ongoing tracking, the market (table, 
processing, etc.) to which the various sources  of eggs (regulated flock, unregulated 
flock, imported, layer hatchery surplus, broiler hatchery surplus) are directed. 
 
The Egg Program of the CFIA inspects all register ed egg grading stations to ensure that proper 
sanitation and operating requirement s are being met, takes environmental samples twice per year 
to detect the presence of Salmonella , and conducts follow-up as appropriate. 
Eggs from S. Enteritidis positive flocks should be divert ed to further processing, as per current 
practices.  Hatchery surplus eggs and eggs from  unregulated flocks that are not operating under a 
HACCP-based program with a te st and divert program for S. Enteritidis, should be  diverted away 
from the table market to processed egg stati ons for pasteurization, as  per Recommendations #13 
and #14.  Tracking of the markets to which differe nt sources of eggs ar e directed will allow 
monitoring and verification of the sources of table eggs and will help direct future versions of 
this guidance.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   21  
Recommendation #19 
Eggs originating from laying flocks wh ose environments tested positive for S. 
Enteritidis should proceed directly to the processed egg station for pasteurization. 
 
If eggs from positive laying flocks are routed through an egg grading station for the purpose of 
transportation, traceability should be maintained by clear identification of the eggs, which should 
also be isolated to prevent cross-contamination with other eggs.  Furthermore, all trucks and 
equipment should be thoroughly cleaned inside and out after receiving the eggs, and if possible, 
the eggs should be the last pickup on the rout e.  Documentation to accompany the eggs should 
include the quantity of eggs, the date of shipment, the transporte r used, the age of the eggs, and 
documentation that the eggs were properly refrigerated. 
8.3.8 Processed egg stations 
 
Recommendation #20 
Shell eggs sent to a processed egg statio n for pasteurization should be kept 
refrigerated. If this is not possible, stor age should be a maximum of 6 days at a 
storage temperature of 20°C or less, or a maximum of 2 days at a temperature 
between 20°C and 30°C.   
 
Ideally, shell eggs to be used for further proc essing should be kept under refrigeration; however, 
this may not be possible in all circumstances. If eggs cannot be kept under refrigeration, the 
times and  temperatures in Recommendation #20, calcula ted from the point of lay, should be 
respected in order to prevent possible pasteuri zation failures. This recommendation stems from 
simulations performed by Health Canada that take into account the growth of S. Enteritidis that 
would occur if eggs originated from  a flock that was infected with S. Enteritidis.  This 
recommendation should be used fo r all shell eggs, since not all flocks of origin will have a 
known S. Enteritidis status, and certain flock infec tions may go undetected even if testing is 
performed.  Eggs which have not been kept unde r appropriate storage c onditions should not be 
accepted for processing. 
The time-temperature combinations for processi ng of eggs were specifically designed to 
inactivate salmonellae in exce ss of the levels that woul d be found in eggs from S. Enteritidis 
positive flocks, under the assumption that the eggs have been kept under refrigeration.  Personnel 
should always use caution when handling raw e ggs, since they may be contaminated with 
Salmonella .  Eggs received from flocks w hose environment tested positive for S. Enteritidis 
should be processed at the end of the day, followe d by the normal sanitization protocol in place.  
Holding time should be minimized and the eggs s hould be isolated.  Their packaging materials 
should also be isolated to pe rmit cleaning and disinfection or disposal.  The environment and 
processed product can be tested to ensure that any S. Enteritidis cells present were inactivated by 
the sanitation and heat treat ment, respectively.      
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   22 8.4 Education campaigns 
The Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella  
Enteritidis  (DeWinter et al. , 2011) identified the importance of storage, handling, and 
preparation practices in both the home and FSI settings.  Substituting pasteurized egg products 
for all pooled shell eggs in FSI settings would decrease the numb er of illnesses by 71%.  A 50% 
reduction in the consumption of raw or lightly  cooked egg meals or recipes would decrease 
illnesses by 8% and 28% in FSI and home settin gs, respectively.  Improving egg storage and 
handling conditions such that yolk membrane breakdown and growth of S. Enteritidis never 
occurred, would decrease the number of illnesses by 76% and 44% of baseline in FSI and home settings, respectively.  Therefore, it is importa nt that educational materials be developed to 
address these issues. 
Egg safety education campaigns targeting the ge neral public will create an understanding of food 
safety issues within the context of the egg i ndustry’s efforts to reduce health risks and the 
public’s right to know about potential hazards in  table eggs.  The information should focus on 
the importance of refrigeration of  shell eggs and also address the use of pasteurized egg products 
as a replacement for shell eggs in raw and ligh tly cooked egg meals and recipes.  The education 
campaign may recommend the use of pasteurize d products in place of all shell eggs for 
immunocompromised groups, or al ternatively, that sh ell eggs should be cooked thoroughly. 
A specific education campaign should target FSI se ttings.  It should incl ude the same general 
information with an additional recommendation to substitute pasteurized products for shell eggs 
pooled in larger quantities.  The campaign shoul d also convey that eggs must be handled and 
prepared in a way that protects the health of clients.  The campaign may also recommend the use 
of pasteurized products in place of all sh ell eggs in FSI set tings consisting of 
immunocompromised groups.  Such education camp aigns could be undertaken as a collaborative 
effort between Health Canada, other fede ral departments and agencies, as well as 
provincial/territorial governm ents and the egg industry. 
 
9. Implementation  
Health Canada is strongly recommending that th ese mitigation strategies be implemented in a 
timely manner. It is expected that industry associations and marketing boards will be active 
partners in communicating this new guidance within their sector.   
As mentioned in 8.3.1, the implementation of  this guidance should result in common 
requirements for all table eggs offered for sale  in Canada.  This would in turn allow the 
elaboration of minimum requirements for tabl e eggs that will pe rmit a harmonization of 
requirements for all table eggs, including imported table eggs. 
The educational portion of this  guidance targeting consumers would be promoted primarily 
through the Canadian Partnership for Consumer Food Safety Education.  
The mechanisms used to assess the effectiven ess of the recommendations included in this 
guidance will be multi-faceted.  It should also be noted that a number of these recommendations 
are currently being at least partially implemented by industr y, varying by jurisdiction.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   23 10. References 
1. Agriculture and Agri-Food Canada ( AAFC). 2006. Canada’s  egg industry. http://ats-
sea.agr.gc.ca/supply/3300_e.htm  (Accessed April 29, 2009).  
2. Boucher, N.  Chief, Hatchery Program, CFIA.  Personal communi cation.  April 18, 2008. 
3. Bucher O, Holley RA, Ahmed R, Tabor H, Nadon C, Ng LK, D'Aoust JY.  2007.  
Occurrence and char acterization of Salmonella from chicken nuggets, strips, and pelleted 
broiler feed. J Food Prot. 70(10):2251-8. 
4. Callaway TR, Dowd SE, Wolcott RD, Sun Y,  McReynolds JL, Edrington TS, Byrd JA, 
Anderson RC, Krueger N, Nisbet DJ. 2009. Evalua tion of the bacterial diversity in cecal 
contents of laying hens fed various molti ng diets by using bacterial tag-encoded FLX 
amplicon pyrosequencing. P oult Sci. 88(2):298-302.  
5. Canadian Egg Marketing Agency (CEMA – now Egg Farmers of Canada).  2002.  
Celebrating our 30th anniversary: a brief history of  national egg supply management.  
Available at: http://www.eggs.ca/Resour ces/default.aspx?Pageid=5   
6. Canadian Egg Marketing Agency (CEMA – now Egg Farmers of Canada).  Personal 
communication (e-mail) from B. Cox, December 10, 2007. 
7. Canadian Food Inspection Agency (CFIA) . 2012. Veterinary Biologics Licensed in 
Canada.  Available at:  http://www.inspection.gc. ca/animals/veterinary-
biologics/licensed- products/eng/1305488042307/1320704013875  (Accessed Apr. 10, 
2012). 
8. Castellan DM, Kinde H, Kass PH, Cutler G,  Breitmeyer RE, Bell DD, Ernst RA, Kerr 
DC, Little HE, Willoughby D, Riemann HP, Ardans A, Snowdon JA, Kuney DR. 2004. 
Descriptive study of California egg layer premises and analysis of risk factors for 
Salmonella enterica  serotype Enteritidis as character ized by manure drag swabs. Avian 
Dis. 48(3):550-61. 
9. Centers for Disease Contro l and Prevention (CDC). 2003. Salmonella  serotype Enteritidis 
outbreak summaries”. Available at: 
http://www.cdc.gov/foodborneoutbreaks/outbreak_data.htm   (Accessed Feb. 25, 2008). 
10. Centers for Disease Control and Preven tion (CDC). 2010.  Investigation update: 
multistate outbreak of human Salmonella Enteritidis infections asso ciated with shell eggs.  
Available at: http://www.cdc.gov/salmonella/enteritidis/  (Accessed Mar. 30, 2012). 
11. Centre for Infectious Disease Prevention and C ontrol, Public Health Agency of Canada.  
National Notifiable Diseases On-Line.  Available at: http://dsol-smed.phac-
aspc.gc.ca/dsol-smed/ndis/c_ind_e.html#top_list  (Accessed June 26, 2006). 
12. Cereno, T.  Chief, Hatchery Program, CFIA .  Presentation at industry – government 
meeting on S. Enteritidis in eggs guidance document.  March 7, 2012. 
13. Codex Alimentarius Commission, Joint FAO/ WHO Food Standards Programme, Codex 
Committee on Food Labelling.  2007.  Draft code  of hygienic practice for eggs and egg 
products (at step 8).  Ali norm 07/30/13.  Available at: 
ftp://ftp.fao.org/codex/ccfl35/fl3504ae.pdf  (Accessed November 26, 2008). 
14. Cormier, R. February 16, 2012.  Calgary’s egg man off to jail for contempt of court. The 
Edmonton Journal. 
15. Cowden JM, Lynch D, Joseph CA, O'Mahony M, Mawer SL, Rowe B, Bartlett CL.  
1989.  Case-control study of infections with Salmonella enteritidis  phage type 4 in 
England. BMJ 299(6702):771-3.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   24 16. Crump JA, Griffin PM, Angulo FJ. 2002. Bacteria l contamination of animal feed and its 
relationship to human foodborne illne ss. Clin Infect Dis. 35(7):859-65. 
17. Davies R, Breslin M. 2001. Environmen tal contamination and detection of Salmonella 
enterica  serovar Enteritidis in laying  flocks. Vet Rec. 149(23):699-704. 
18. Davies R, Breslin M. 2004. Observations on Salmonella  contamination of eggs from 
infected commercial laying flocks where vaccination for Salmonella enterica  serovar 
Enteritidis had been used. Avian Pathol. 33 (2), 133 ‐144. 
19. DeWinter LM, Ross WH, Couture H, Farber  JF. 2011. Risk assessment of shell eggs 
internally contaminated with Salmonella  Enteritidis. Int Food Risk Anal J 1:40-81. 
20. Donalson LM, McReynolds JL, Kim WK, Ch alova VI, Woodward CL, Kubena LF, 
Nisbet DJ, Ricke SC. 2008. The influence of a fructooligosaccharide prebiotic combined 
with alfalfa molt diets on the ga strointestinal tract fermentation, Salmonella enteritidis  
infection, and intestinal shedding in laying hens. Poult Sci.  87(7):1253-1262. 
21. EFC, 2012. Personal communication (e-m ail) from C. Nash, March 30, 2012. 
22. European Food Safety Authority (EFSA). 2008. Microbiological ri sk assessment in 
feedingstuffs for food-producing animals.  EFSA J, 720: 1-84. 
23. European Food Safety Authority (EFSA). 2010. Scientific opinion on the quantitative 
estimation of the public impact of set ting a new target for the reduction of Salmonella  in 
laying hens. EFSA J. 8(4) :1546-1632.  Available at: 
http://www.efsa.europa.eu/en/scdocs/ scdoc/1546.htm (Accessed April 3, 2012). 
24. Everett, D.  Manager, Environmental Pub lic Health, Alberta Health and Wellness. 
Personal communication (e-mail) April 16, 2012. 
25. Garber L, Smeltzer M, Fedorka-Cra y P, Ladely S, Ferris K.  2003.  Salmonella enterica 
serotype Enteritidis in table egg layer hous e environments and in mice in U.S. layer 
houses and associated risk fact ors.  Avian Dis. 47:134-142. 
26. Gast, R. Bacterial infect ion of eggs, chapter 1.  In Mead, G.C. (ed.), Food safety control 
in the poultry industry, p. 1-20.  2005.  Woodhead Publishing Limited, Abington, 
England. 
27. Gast RK.  2007.  Serotype-specific and serot ype-independent strategies for preharvest 
control of food-borne Salmonella in  poultry.  Avian Dis. 51(4):817-28. 
28. Gast RK, Guraya R, Guard-Bouldin J, Holt PS. 2008.  Multiplication of Salmonella 
Enteritidis on the yolk membrane and penetratio n to the yolk contents at 30°C in an in 
vitro egg contamination model.   J Food Prot. 71(9):1905-9. 
29. Golden NJ, Marks HH, Coleman ME, Schroeder CM, Bauer NE, Schlosser WD.  2008.  
Review of induced molting by feed removal and contamination of eggs with Salmonella 
enterica serovar Enteritidits.  Vet Microbiol. 131:215-228. 
30. Gutierrez O, Zhang C, Caldwell DJ, Carey JB, Cartwright AL, Bailey CA. 2008. Guar 
meal diets as an alternative appr oach to inducing molt and improving Salmonella  
enteritidis  resistance in late-phase laying hens. Poult Sci. 87(3): 536-40. 
31. Health Canada. 2003.  Canadian In tegrated Surve illance Report:  Salmonella, 
Campylobacter , pathogenic E. coli , and Shigella,  from 1996 to 1999.  Can. Commun. 
Dis. Rep. 29S1. 
32. Health Canada, Food Directorate. 2009. Bureau  of Microbial Hazards Advisory Opinion 
on the Acceptability of Eggs for Proce ssing at Egg Breaking Facilities (RAO 270). 
33. Holt PS. 1993. Effect of induced molting on the susceptibility of White Leghorn hens to a 
Salmonella enteritidis  infection. Avian Dis. 37(2):412-7.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   25 34. Holt PS.  2003.  Molting and Salmonella enterica serovar Enteritidis infection: the 
problem and some solutions.  Poult Sci. 82:1008-1010. 
35. Humphrey TJ, Baskerville A, Mawer S, Rowe B, Hopper S. 1989. Salmonella enteritidis  
phage type 4 from the contents of intact eggs: a study involving naturally infected hens. 
Epidemiol Infect. 103(3):415-23. 
36. Khakhria R, Woodward D, Johnson WM, Poppe C. 1997. Salmonella  isolated from 
humans, animals and other sources in Ca nada, 1983-92. Epidemiol Infect 1997; 119:15-
23. 
37. Kinde H, Castellan DM, Kerr D, Campbe ll J, Breitmeyer R, Ardans A. 2005. 
Longitudinal monitoring of two commercial layer flocks and thei r environments for 
Salmonella enterica  serovar Enteritidis and other salm onellae.  Avian Dis. 49 (2):189-94. 
38. Murase T, Chiba K, Sato T, Otsuki K, Holt PS. 2006. Effects of different molting 
procedures on incidence of Salmonella  infection in flocks of naturally contaminated 
laying hens in a commercial egg-produci ng farm by detection of yolk antibodies to 
Salmonella  in eggs. J Food Prot 69(12): 2883-2888. 
39. Nakamura M, Nagamine N, Takahashi T, Suzuki S, Sato S. 1994. Evaluation of the 
efficacy of a bacterin against Salmonella enteritidis  infection and the effect of stress after 
vaccination. Avian Dis. 38(4):717-24. 
40. Patrick ME, Adcock PM, Gomez TM, Altekr use SF, Holland BH, Tauxe RV, Swerdlow 
DL. 2004. Salmonella  Enteritidis infections, United States, 1985-1999. Emerg Infect Dis. 
10(1):1-7. 
41. Poppe C, Irwin RJ, Forsberg CM, Clarke RC, Oggel J. 1991. The prevalence of 
Salmonella enteritidis and other Salmonella spp. among Canadian registered commercial 
layer flocks.  Epidemiol Infect. 106(2):259-70. 
42. Poppe C, Johnson RP, Forsberg CM, Irwin RJ.  1992.  Salmonella enteritidis and other 
Salmonella in laying hens and eggs from flocks with Salmonella in their environment.  
Can J Vet Res. 56(3):226-32. 
43. Public Health Agency of Canada (PHAC).   2004.  Laboratory Surveillance Data for 
Enteric Pathogens in Canada, Annual Summary 2001.  Available at: http://www.nml-
lnm.gc.ca/NESP-PNSME/index-eng.htm  (Accessed April 29, 2009). 
44. Public Health Agency of Canada (PHAC).  2005.  Laboratory  Surveillance Data for 
Enteric Pathogens in Canada.  A nnual Summary 2002 and 2003. Available at: 
http://www.nml-lnm.gc.ca/NESP-PNSME/index-eng.htm  (Accessed April 29, 2009). 
45. Public Health Agency of Canada (PHAC).  2007a.  Laboratory Surveillance Data for 
Enteric Pathogens in Canada, Annual Summary 2005. Available at: http://www.nml-
lnm.gc.ca/NESP-PNSME/index-eng.htm  (Accessed April 29, 2009). 
46. Public Health Agency of Canada (PHAC).   2007b.  Laboratory Surveillance Data for 
Enteric Pathogens in Canada, Annual Summary 2006. Available at: http://www.nml-
lnm.gc.ca/NESP-PNSME/index-eng.htm  (Accessed April 29, 2009). 
47. Public Health Agency of Canada (PHAC).  2009. National Notifiable Diseases On-Line. 
Available at: http://dsol-smed.phac-aspc.gc.c a/dsol-smed/ndis/list_e.html  (Accessed 
April 29, 2009). 
48. Slade, D. February 29, 2012. Catering compa ny fined for serving bad eggs. The Calgary 
Herald.  
Guidance on Reducing the Risk of Salmonella  Enteritidis in Canadian Shell Eggs 
 
 
Bureau of Microbial Hazards, Food Directorat e, Health Products and Food Branch   26 49. St Louis ME, Morse DL, Potter ME, DeMelf i TM, Guzewich JJ, Tauxe RV, Blake PA.  
1988.  The emergence of grade A eggs as a major source of Salmonella enteritidis 
infections: new implications for the cont rol of salmonellosis.  JAMA. 259(14):2103-7. 
50. Statistics Canada. 2007.  Poultry and E gg Statistics, October to December 2006.  
Catalogue no. 23-015-XIE.  Available at: http://www.statcan.gc. ca/bsolc/olc-cel/olc-
cel?catno=23-015-X&CHROPG=1&lang=eng  (Accessed February 17, 2009). 
51. Taylor M, Leslie M, Ritson M, Stone J,  Cox W, Hoang L, Galanis E, Outbreak 
Investigation Team. 2012. Investigati on of the concurrent emergence of Salmonella 
Enteritidis in humans and poultry in Br itish Columbia, Canada, 2008-2010.  Manuscript 
pending publication in Zoonoses and Public Health (doi: 10.1111/j.1863-
2378.2012.01500.x). 
52. Wales A, Breslin M, Carter B, Sayers R, Davies R. 2007. A longitudinal study of 
environmental salmonella contamination in cag ed and free-range layer flocks.  Avian 
Pathol. 36:187-197. 
53. Wales A, Breslin M, Davies R.  2006.  Semiqua ntitative assessment of  the distribution of 
Salmonella in the environment of caged layer fl ocks.  J Appl Mi crbiol 101:309-318. 
54. Wray C, Davies RH, Evans SJ. Salmonella infection in poultry: the production 
environment, chapter 11.  In Richardson RI & Mead GC (eds .), Poultry Meat Science, p. 
257-275, 1999.  CABI Publishi ng, Oxon, United Kingdom.