Consultation - Guidance for Industry on Reducing the Risk of Salmonella Enteritidis in Canadian Shell Eggs
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The summary of comments is available. To obtain an electronic copy of the document, Report on Health Canada's Consultation for Guidance on Reducing the Risk of Salmonella Enteritidis in Shell Eggs Produced in Canada, please contact our publications office or send an e-mail to firstname.lastname@example.org with the subject heading "HPFB BMH Consultation Summary of Comments Salmonella Enteritidis Shell Eggs".
The final guidance document entitled Health Canada Guidance on Reducing the Risk of Salmonella Enteritidis in Shell Eggs Produced in Canada is also now available.
Table of Contents
- 1. Scope
- 2. Definitions
- 3. Introduction
- 4. Background
- 5. Consultation
- 6. Risk Assessment Overview
- 7. Guidance to Improve the Microbiological Quality of Shell Eggs
- 7.1 Guidance for the Production of Table Eggs
- 7.2 Guidance when Eggs are Implicated in Human Illness
- 7.3 Post-Production Guidance for Table Eggs
- 7.4 Education campaigns
- 8. Implementation
- 9. References
- 10. Consultation Workbook
Health Canada's Bureau of Microbial Hazards is seeking comments on its proposed guidance document on Salmonella Enteritidis in shell eggs. The purpose of this guidance document is to reduce the risk of foodborne illness due to S. Enteritidis in shell eggs by providing guidance regarding the microbiological safety of shell eggs produced by domestic hens (Gallus gallus) offered for sale on the table market in Canada. This guidance document, developed as a joint effort between Health Canada, the Canadian Food Inspection Agency, and the Public Health Agency of Canada, takes into account the roles and responsibilities of industry, government and consumers.
A risk assessment entitled "Risk Assessment of Shell Eggs Internally Contaminated with Salmonella Enteritidis" was published by Health Canada in 2011 in International Food Risk Analysis Journal, an open access publication. The risk assessment examined the effect of risk management options and directed the development of the policy. The risk assessment is available at the publisher's website.
This document is intended to provide guidance for industry to reduce the risk 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 intervention strategies to manage the microbiological safety of shell eggs produced by domestic hens (Gallus gallus) offered for sale on the table market in Canada. It was developed using a health risk assessment approach (Health Canada, 2011). Difficulties in identifying S. Enteritidis in eggs has resulted in controls being put in place at the level of the laying flock. When S. Enteritidis is identified in the environment of a laying flock, the eggs from that flock are sent to pasteurization for the lifetime of the flock. Therefore, this document also provides guidance to industry regarding best practices for the egg industry. Although the guidance in this document mainly involves the egg industry and its components, due to the overlaps between the egg industry and the broiler industry at various stages, it was necessary that this guidance document also make recommendations for the broiler industry.
This guidance document represents a consensus-based standard that should be implemented in the egg industry on a voluntary basis with the possibility of regulatory backstops in the future, if warranted.
Food safety enforcement bodies at the federal, provincial, and territory level may use this guidance document as a reference to assess adherence of the egg industry to good agricultural practices. 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.
Food safety is a shared responsibility between industry and government. It is Health Canada's role to set food safety standards in collaboration with its partners and stakeholders. The role of the Canadian Food Inspection Agency (CFIA) is to enforce these standards. Industry has a responsibility to develop, adopt, and implement good manufacturing practices and controls that are conducive to the production of safe eggs. In addition to government agencies and food industries working diligently at minimizing the exposure to S. Enteritidis, consumers also have an important role to play in the farm-to-fork continuum in adopting safe egg handling and preparation practices.
For the purpose of this document the following definitions apply.
Salmonella is an important foodborne pathogen worldwide. 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 salmonellosis range from mild to severe diarrhea, abdominal pain and vomiting, as well as fever accompanied by headache and chills. In cases of severe diarrhea, dehydration may lead to hypotension, cramps, oliguria and uraemia. The vast majority of cases comprise acute illness that lasts a few days, with recovery occurring within a week. Death is uncommon except in the very young, very old, or immunocompromised. Small proportions of cases develop bacteremia or meningitis, or may develop localised infections causing abscesses, arthritis, cholecystitis, endocarditis, pericarditis or pneumonia. Long-term sequelae resulting from salmonellosis can include malabsorption of essential nutrients (which can result in a compromised immune system and may lead to infection), allergy, reactive arthritis, autoimmune disorders and neoplasia. Although reactive arthritis is usually of short duration, some patients may develop chronic disease and patients with certain underlying conditions (for example, haemoglobin abnormalities) may be prone to complications.
For S. Enteritidis infections, eggs have been established as a major vehicle for human cases. Most serotypes of Salmonella contaminate shell eggs on the exterior shell surface, which is referred to as horizontal transmission. The organisms may gain entry to the interior contents by cracks in the shell or by other circumstances that can lead to eggshell penetration (for example, time and temperature abuse, improper egg washing). Scientifically designed and tested egg washing protocols used at egg grading stations 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. 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 tissues 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 the nutrient rich yolk and grow rapidly, and by consumers' known preferences for eating raw and lightly-cooked eggs.
There has been an increase in reports of S. Enteritidis outbreaks associated with unusual vehicles such as almonds and sprouted seeds. Reports of S. Enteritidis outbreaks associated with eggs may have decreased due to the fact that eggs are known to be an important vehicle of S. Enteritidis. However, eggs will remain an important vehicle of infection due to trans-ovarian transmission into intact eggs. In the United States, from 1985 through 2002, 73% to 80% of S. Enteritidis outbreaks have been identified as egg-related (CDC, 2003; Patrick et al., 2004).
In Canada, Salmonella has been the second most common enteric bacterial pathogen since at least 1997, judging by Salmonella isolates referred to the National Microbiology Laboratory (PHAC, 2004) and cases reported through the national notifiable disease program (PHAC, 2009). S. Enteritidis consistently ranks among the top three serovars associated with human illness in Canada since at least 1995, and the top five since 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 prevalent serotype, having represented 28% of all salmonellosis cases in 2005 and 23% in 2006 (PHAC, 2007ab).
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 oviducts 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 intact 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 determine the extent of the problem with S. Enteritidis in Canada (Poppe et al., 1991; Poppe et al., 1992). In 1996, Health Canada developed an interim policy on the issue and the egg industry began to divert eggs to further processing to inactivate the organisms, when S. Enteritidis was identified in the environment 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 Clean™, and was also modified to include free-range, free-run and specialty flocks such as organic operations. This On-Farm Food Safety program completed technical reviews by the CFIA in 2004 and 2007. The program includes a number of practices intended to minimize the possibility of introducing Salmonella to a laying flock, as well as on farm inspections conducted by provincial and federal officers that provide each egg producer with a rating and suggestions for improvement. Among the regulated laying flocks that operate under the Canadian supply management system, EFC has been able to achieve over 90% participation in Start Clean - Stay Clean™, and 100% of egg producers are currently being tested for S. Enteritidis. Currently, the program is implementing an insurance program that will 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) and EFC data for imported table eggs (CEMA, 2007). However, hatching eggs that proceed to the table market, sales at the farm gate, and sales at farmers' markets are not accounted for in the estimate and therefore it 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-registered grading stations, which must meet requirements, including temperature and humidity controls for storage of eggs, and other hygienic requirements. During the grading process, cracked eggs may only meet the grade Canada C, and thus are sent for pasteurization. Dirty eggs do not meet any Canada grade; they are considered unfit for human consumption. Grading stations are monitored regularly by the CFIA, and twice per year undergo environmental sampling for salmonellae. Positives are serotyped and corrective actions are 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 that grade A table eggs in Canada can originate from a number of sources, not just from regulated flocks. In general, there is very limited data about these other sources of eggs including their proportion of market share, flock management and egg storage and handling practices where they relate to the risk of S. Enteritidis, and the proportion of illnesses attributed to eggs from these sources. Therefore, although this guidance document addresses recommendations for table eggs from regulated flocks through the improvement of existing On-Farm Food Safety programs, it also makes recommendations recognizing that the additional sources of eggs for the table market also represent a potential risk to consumers. The coverage of the On-Farm Food Safety programs and governmental surveillance and monitoring programs in place to reduce the risk of S. Enteritidis in grade A table eggs, do not necessarily extend to eggs originating from other sources and therefore sources of table eggs outside of the regulated flocks may represent an increased risk to consumers.
This document has been prepared by experts from Health Canada, CFIA, and the Public Health Agency of Canada (PHAC). Input has been sought from key industry stakeholders including the Egg Farmers of Canada (EFC), the Canadian Hatching Egg Producers (CHEP), and the Canadian Poultry and Egg Processor's Council (CPEPC), and was given full consideration in the development of this guidance.
As part of the review of the guidance document, Health Canada is hosting a public consultation to gather opinions from the public, veterinary professionals, agriculture professionals, health professionals, people in the food industry, and others who might be affected by the guidance document. Your input about the guidance document is very important to the success of Health Canada's review. A report from the public consultations will be posted on Health Canada's Web site.
6. Risk Assessment Overview
A risk assessment entitled "Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella Enteritidis" was completed by Health Canada in 2011 (Int Food Risk Anal J, submitted for publication). The development of the risk assessment involved an extensive literature review, as well as consultation with experts from the CFIA and PHAC.
The risk assessment highlighted the fact that eggs are consumed by every segment of the Canadian population. Annual total egg consumption in Canada dropped from 23 dozen per person in 1960 to 14.4 dozen in 1995. However, in the past few years, mainly due to the increasing demand from the processing egg sector, egg consumption has increased, reaching 15.6 dozen per person in 2005 (Agriculture and Agri-Food Canada, 2006). Since 1995, per capita processed egg consumption has increased by 30% (Agriculture and Agri-Food Canada, 2006). In 2005, the total production 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 for use in processed egg products. Non-susceptible and susceptible populations consume an average of 74.7% and 79.0% of shell eggs, respectively, in a home setting, with the balance of consumption occurring in a food service and institutional (FSI) setting. In total, non-susceptible 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 meals in home settings, and 0.04, 11.0, and 89.0% in FSI settings.
The results of the risk assessment 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 consumption of a serving from a contaminated egg than non-susceptible individuals. Illnesses were found to be disproportionate to exposures, 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 suggest that risk management options that target 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 in the risk assessment to determine conditions under which the prevalence of contaminated eggs would be reduced, and those under which the number of illnesses per contaminated egg would be reduced, resulting in the following observations:
- Full vaccination of all laying flocks would reduce the number of illnesses to 4% of baseline (no vaccination) levels. Targeted (in other words, when the previously housed flock tested positive) vaccination of all flocks 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 and 8-10 weeks before the end of lay, with diversion of eggs from flocks found to be occupying positive environments, would reduce the number of illnesses to between 2% and 29% of baseline levels, depending upon whether the majority of infections occurred prior to the laying cycle or during the laying cycle, 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 settings) of baseline.
7. 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 from 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 passage of the organisms by the transovarian route, control measures that will ensure the microbiological safety of shell eggs with respect to S. Enteritidis will be most effective if they were to occur along the entire supply chain of the egg industry, from the grandparent 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 also influenced the types of risk management options that were explored to improve current 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. Although there is no data available as to the prevalence of S. Enteritidis among the flocks producing these eggs, the control programs and surveillance in place for the regulated flocks and their ancestors do not necessarily extend to these flocks.
7.1 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. Flock 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 (Health Canada, 2011).
Preventing S. Enteritidis infection of laying flocks requires application of S. Enteritidis testing and/or control measures from the breeding flocks through to the laying flocks themselves. Testing programs have the added benefit of providing information as to the importance of various sources of S. Enteritidis infection, so that future HACCP-based control programs can be modified to adequately control for these sources.
7.1.1 Production of hatching chicks
Chicken hatchery supply flocks should be free of S. Enteritidis. The means to achieve this need to be addressed, and consideration should be given to the use of harmonized methods which would result in a greater reliability of test results.
Due to an industry-led program that comprises testing and control measures, the hatchery supply flocks for the layer industry have rarely been identified as a source of S. Enteritidis over the past 10 years (Boucher, 2008). However, this is not the case for the broiler sector and this source of S. Enteritidis could result in cross-contamination at hatcheries producing both egg-type and meat-type chicks as well as at other stages where broiler operations may overlap egg operations (for example, common equipment or catching crews). It has been brought to Health Canada's attention that an investigation of human illnesses and outbreaks of S. Enteritidis pointed to laying flocks that were infected with S. Enteritidis due to the numerous overlaps with the broiler sector.
The CFIA currently performs fluff testing every six weeks in hatcheries 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. It is anticipated that layer hatchery supply flocks are already close to meeting this recommendation, but that broiler hatchery supply flocks will need more time to work towards this recommendation.
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 only notification of positive fluff test results to the industry stakeholder and the appropriate provincial egg board, who then decides upon the course of action. Exposure of egg-type chicks to S. Enteritidis should be assessed using fluff testing results and other bacteriological monitoring programs, together with consideration of the protocols in use at the hatchery.
7.1.2 Pullet rearing
Pullets should be reared in environments separated sufficiently from broiler operations as well as other poultry and other livestock operations, so as to prevent cross-contamination.
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.
7.1.3 S. Enteritidis testing in pullet and laying flocks
Pullets should be tested twice during the pullet-rearing stage. Laying flocks that are supplying shell eggs for the table market should be tested a minimum of twice per laying cycle.
Laying hens can be infected through horizontal or vertical transmission, so testing should be practiced in order to detect both sources of infection. Test results should be provided to the CFIA to enable ongoing monitoring of the situation. Testing can also provide verification of the efficacy of On-Farm Food Safety programs in reducing the prevalence of Salmonella in laying flocks.
Flocks should be tested for S. Enteritidis by performing environmental sampling, which is in line with current practices among regulated flocks. Currently, flock testing 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, approximately 8 to 10 weeks before the end of the laying cycle. Although the timing of this test provides information about the environment that the subsequent flock will occupy, it does not provide risk mitigation for the initial 42 to 44 weeks of egg production by that flock.
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 number of times a flock is tested increases, and as environmental test sensitivity increases (Health Canada, 2011). Depending upon the relative importance of vertical and horizontal transmission of S. Enteritidis, two tests during the approximately 52 week laying cycle of all regulated flocks, plus diversion of eggs to further processing, 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 20 and 26 weeks of age). This is a period of time when the birds are physiologically stressed, and testing will effectively detect infected flocks. The timing of this test will also mitigate the risk of contaminated eggs produced from flocks infected early in the laying cycle. The second test should occur when the laying flock is between 46 and 64 weeks of age.
Current testing protocols dictate a minimum of one test, which generally occurs 8-10 weeks before the end of lay (corresponding 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 physiological stress of the laying flock 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 receipt of test results usually occurs after the end of the laying cycle, thereby not permitting the diversion 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 there 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 the two tests so that the tests are fairly well-distributed over the 52 week laying cycle.
The practice of induced moulting of laying flocks should be discontinued. Any moulted laying flocks should undergo increased testing.
Although moulting is rarely practiced in Canada, flocks that are moulted experience increased stress and, depending upon the procedure used to induce moulting, may be 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 contamination in continuously occupied houses (Wales et al., 2007). Post-moult laying flocks should be tested every 3 months, with the first test for the post-moult flock occurring within 5 weeks of moult.
The recommendation to discontinue moulting may be reconsidered in the future if moulting procedures are developed that do not result in increased risks of flock infection and egg contamination.
All provinces and territories should use the same sampling protocol and methodology to perform environmental testing of laying flocks for S. Enteritidis. Sampling in the flock environment should comprise a variety of samples.
Provincial egg marketing boards also specify the protocol and methodologies for S. Enteritidis testing. Use of the same sampling protocol and methodology helps to ensure consumer safety and makes data comparisons possible. The determination of which sampling protocols and methodologies will form the basis of the testing program should be based on best practices, determined by a working group comprised of appropriate stakeholders including EFC, provincial egg boards, poultry veterinarian experts, the CFIA, and 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, egg 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. Dust 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). A proportion of bird mortalities should be tested for S. Enteritidis. Since samples from agricultural environments are expected to have a higher load of background microbiota, including other Salmonella serovars, the method used for isolation must permit sufficient resuscitation and have a sufficiently selective environment in which salmonellae can outcompete the other microorganisms present in the sample. Therefore, methods intended for food and food manufacturing environments should not be used without sufficient validation.
7.1.4 Actions to be taken upon finding S. Enteritidis-positive flocks
When the environment of a flock tests positive for S. Enteritidis, it is recommended that the eggs from that flock be diverted for further 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 with the subsequent flock, and that an investigation be pursued by the provincial egg board or EFC to review biosecurity measures and suggest on-farm improvements as corrective actions. Where investigations are performed, the data collected regarding the potential sources of S. Enteritidis contamination can be used to improve the On-Farm Food Safety program.
Pullet flocks that test positive for S. Enteritidis should not be supplied to egg producers for use as laying hens.
7.1.5 On-Farm Food Safety program recommendations
Laying flocks that are supplying shell eggs for the table market should participate in a HACCP-based On-Farm Food Safety program that addresses 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 should be given to the following:
- Poultry feed
- Sources of possible cross-contamination such as equipment, personnel and vectors
- Biosecurity practices between different operations (for example, layer or pullet flocks and broiler flocks on the same or different premises)
S. Enteritidis has recently been found in 2% of (2 of 111) finished pelleted poultry feed samples (Bucher et al., 2007), suggesting that feed may represent a continued source of exposure. Producers may wish to select feed for laying hens, pullets, and egg-type chicks that has undergone a treatment (for example, heat treatment) that has been verified to inactivate S. Enteritidis. Egg producers mixing feed on-farm should have their feed and/or feed ingredients tested regularly for S. Enteritidis.
7.1.6 Vaccination programs
Laying flocks that are moving into houses that tested positive for S. Enteritidis while being inhabited by the previous laying flock, should be vaccinated.
The relative prevalence of S. Enteritidis in vaccinated versus unvaccinated flocks has not been reported, but 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 flocks is estimated to reduce contaminated egg prevalence by 96% (Health Canada, 2011). It should be noted that veterinary vaccines are licensed by the Canadian Centre for Veterinary Biologics of the CFIA.
Vaccination should never be used as a substitute for cleaning and disinfection 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 production of contaminated eggs, should a flock become infected.
A vaccinated flock would still be subject to S. Enteritidis testing (as per 7.1.3), and the same actions would be taken in the event of a positive result.
As an alternative to vaccination, the use of probiotics as a means of reducing Salmonella spp. infections may be considered in the future. Probiotics administered to chicks might prevent or decrease colonization of laying hens by S. Enteritidis, by extension resulting in a decrease in contaminated egg prevalence. However, a prerequisite for this would be the approval of probiotic products for such usage, by the Veterinary Drugs Directorate of Health Canada.
7.2 Guidance when Eggs are Implicated in Human Illness
The Public Health Agency of Canada uses a variety of tools, such as the National Enteric Disease Surveillance Program and PulseNet Canada, to perform surveillance and investigate clusters or outbreaks of human illnesses. When eggs are implicated in S. Enteritidis illness and confirmed either epidemiologically or by isolation of the organism 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 should undergo bacteriological examination for S. Enteritidis. Eggs from a positive flock or epidemiologically 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 7.3.8). If eggs from a positive flock are being sold at retail, 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.
7.3 Post-Production Guidance for Table Eggs
Additional recommendations for the safe production 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 not stem directly from the risk assessment.
Any egg producer, regardless of size, may put consumers at risk by supplying eggs for the table market from a flock infected with S. Enteritidis. In addition, eggs that are not stored or handled in a way that minimizes the S. Enteritidis hazard may put consumers at risk. The goal of this section is to achieve a high level of consumer safety by recommending measures to equalize the microbiological risks associated with different sources of eggs.
7.3.1 Imported shell eggs destined for the table market
Imported shell eggs should only be sourced from foreign exporters who can certify that eggs originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all 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. As of 2008, the minimum standards under which Canadian eggs are produced by the regulated laying flocks include the following:
- Participation in a HACCP-based control program
- Mandatory S. Enteritidis environmental testing of laying flock at least once during the laying cycle
- ≥ 40 sites sampled per flock
- Swabs or samples (dust, fluff, scrapings) may be used
- Samples undergo a culture-based Salmonella detection method
Several egg producers in the United States participate in egg quality assurance programs that include flock testing. It appears that the control programs in at least 5 states (PA, MD, NY, OH, SC) and that are used by the United Egg Producers, include flock testing for S. Enteritidis.
The importation process for shell eggs (for both global and supplemental import permits) should allow effective traceforward investigations.
It may be necessary for supplementary table egg imports to proceed through only one sourcing body to ensure that traceability information is available in a timely manner and that the table eggs are being produced by a laying flock meeting the above requirements.
It is anticipated that the implementation of the 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.
7.3.2 Surplus hatching eggs
Surplus hatching eggs should proceed to processed egg stations for pasteurization, unless the eggs originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all environmental test results consistently being negative for S. Enteritidis.
Surplus hatching eggs (that have not undergone any portion of the setting or incubation process) from broiler breeder or layer breeder flocks are subject to different flock management practices and egg storage parameters. Section 4(e) of the Egg Regulations states that eggs that have been 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 food safety requirements established for laying flocks (for example, veterinary drugs).
7.3.3 Table eggs from unregulated and small producers
Shell eggs being offered for sale on the table market should originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all environmental test results consistently being negative for S. Enteritidis.
Table eggs from flocks that are not operating under HACCP-based principles and are not following a test and divert program for S. Enteritidis, pose a higher risk of salmonellosis for the consumer. All laying flocks that are producing eggs for the table market, regardless of size, including grandfathered flocks and specialized flocks, should operate under HACCP-based principles including an environmental testing and egg diversion program for S. Enteritidis (7.1.3 and 7.1.4). Table eggs from unregulated flocks not complying with the recommendations in this guidance document should not be supplied for the table market, but should be diverted for further processing.
7.3.4 Sale of ungraded shell eggs
Only graded eggs should be permitted for sale at farmers' markets, as well as in retail environments, restaurants and foodservice institutions.
The absence of grading requirements, standards, and inspections for shell eggs, together with the absence of programs addressing food safety concerns among egg producers, will result in a greater likelihood of the internal and external contamination of ungraded eggs with Salmonella spp. and S. Enteritidis. Sales of ungraded eggs at farmers' markets may further increase the risk due to issues with traceability and storage temperatures. Eggs offered for sale at farmers' markets have been known to be mixed from different sources or placed into reused egg cartons. In the event of illness, a traceback investigation may identify a farmers' market but not be able to identify the flock of origin, preventing public health action. Reuse of egg cartons may lead to external shell contamination. Furthermore, the storage conditions of eggs during transit and sales at farmers' markets have been known to exceed the maximum of 10°C required for graded eggs intended for the retail market.
7.3.5 Sale of cracked eggs
Cracked eggs should not be offered for sale as table eggs. Cracked eggs should only be sold to:
- federally-licensed processing stations for pasteurization, or
- food processing plants operating under Good Manufacturing Practices, with the condition that the egg ingredients receive a heat treatment equivalent to pasteurization (in other words, validated for a minimum 5-log reduction of S. Enteritidis).
Cracked shells permit the penetration of all salmonellae into eggs and 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 for sale as table eggs. This is also an internationally accepted hygiene standard for eggs (Codex Alimentarius Commission, 2007).
7.3.6 Refrigeration of shell eggs
All sectors involved in egg production should ensure that their processes respect the prompt refrigeration of eggs, in order to maintain the microbiological quality of eggs.
The Canadian Egg Regulations regulate the required temperatures of eggs at registered grading stations. Ungraded eggs, Nest Run eggs, and eggs bearing a dye mark are to be stored 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 September, 2008). The egg grading station is to release eggs for transport only into refrigerated trucks, so that the temperature of the eggs cannot increase during transit. When eggs reach retail, they should be handled as a perishable food to be kept refrigerated. This is under municipal jurisdiction and usually requires refrigeration at 4°C or less.
A recent study has shown that as little as 12 hours at 30°C permitted S. Enteritidis penetration from the vitelline membrane into the yolk in 11.5% of eggs inoculated in vitro (Gast et al., 2008). At the farm level, producers should attempt to collect 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 the length of time at which eggs are held at temperatures above refrigeration. Where on-farm holding is necessary, the microbiological quality of the ungraded eggs should be maintained by holding at no more than 13°C with 70 to 85% relative humidity. A lower temperature threshold of 10°C is suggested for storage on-farm 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 contents, resulting in external shell contaminants being drawn into the egg (Gast, 2005). As the shell eggs proceed through grading stations and into retail settings, the storage temperature continues to be reduced further to help preserve the quality and safety of the eggs.
7.3.7 Egg-grading stations
Egg-grading stations should include in their 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 registered egg grading stations to ensure that proper sanitation and operating requirements are being met, and takes environmental samples twice per year to detect the presence of Salmonella.
Eggs from S. Enteritidis positive flocks should be diverted 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 test and divert program for S. Enteritidis, should be diverted away from the table market to processed egg stations for pasteurization, as per Recommendations #13 and #14. Tracking of the markets to which different sources of eggs are directed will allow monitoring and verification of the sources of table eggs and will help direct future versions of this guidance.
Eggs originating from flocks whose environments tested positive for S. Enteritidis should proceed directly to the processed egg station for pasteurization.
If eggs from positive 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 route. Documentation to accompany the eggs should include the quantity of eggs, the date of shipment, the transporter used, the age of the eggs, and documentation that the eggs were properly refrigerated.
7.3.8 Processed egg stations
Shell eggs sent to a processed egg station should be kept under refrigeration, or stored for a maximum of 6 days at storage temperatures of 20°C or less, or stored for a maximum of 2 days for temperatures between 20°C and 30°C.
Ideally, shell eggs to be used for further processing 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, calculated from the point of lay, should be respected in order to prevent possible pasteurization 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 for all shell eggs, since not all flocks of origin will have a known S. Enteritidis status, and certain flock infections may go undetected even if testing is performed. Eggs which have not been kept under appropriate storage conditions should not be accepted for processing.
The time-temperature combinations for processing of eggs were specifically designed to inactivate salmonellae in excess of the levels that would 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 eggs, since they may be contaminated with Salmonella. Eggs received from flocks whose environment tested positive for S. Enteritidis should be processed at the end of the day, followed by the normal sanitization protocol in place. Holding time should be minimized and the eggs should be isolated. Their packaging materials should also be isolated to permit 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 treatment, respectively.
7.4 Education campaigns
The Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella Enteritidis (Health Canada, 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 number 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 settings, 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 important that educational materials be developed to address these issues.
Egg safety education campaigns to target the general public will create an understanding of food safety issues within the context of the egg industry'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 lightly cooked egg meals and recipes. The education campaign may recommend the use of pasteurized products in place of all shell eggs for immunocompromised groups, or alternatively, that shell eggs should be cooked thoroughly.
A specific education campaign should target FSI settings. It should include the same general information with an additional recommendation to substitute pasteurized products for shell eggs pooled in larger quantities. The campaign should 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 shell eggs in FSI settings consisting of immunocompromised groups. Such education campaigns could be undertaken as a collaborative effort between Health Canada, other federal departments and agencies, as well as provincial/territorial governments and the egg industry.
It is expected that industry associations and marketing boards will be active partners in communicating this new guidance within their sector.
As mentioned in 7.3.1, 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 table eggs that will permit 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 effectiveness 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 industry, varying by jurisdiction.
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- 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/Resources/default.aspx?Pageid=5
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- Davies R, Breslin M. 2001. Environmental contamination and detection of Salmonella enterica serovar Enteritidis in laying flocks. Vet Rec. 149(23):699-704.
- Garber L, Smeltzer M, Fedorka-Cray P, Ladely S, Ferris K. 2003. Salmonella enterica serotype Enteritidis in table egg layer house environments and in mice in U.S. layer houses and associated risk factors. Avian Dis. 47:134-142.
- Gast, R. Bacterial infection 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.
- Gast RK. 2007. Serotype-specific and serotype-independent strategies for preharvest control of food-borne Salmonella in poultry. Avian Dis. 51(4):817-28.
- Gast RK, Guraya R, Guard-Bouldin J, Holt PS. 2008. Multiplication of Salmonella Enteritidis on the yolk membrane and penetration to the yolk contents at 30°C in an in vitro egg contamination model. J Food Prot. 71(9):1905-9.
- 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.
- Health Canada. 2003. Canadian Integrated Surveillance Report: Salmonella, Campylobacter, pathogenic E. coli, and Shigella, from 1996 to 1999. Can. Commun. Dis. Rep. 29S1.
- Health Canada, Food Directorate. 2009. Bureau of Microbial Hazards Advisory Opinion on the Acceptability of Eggs for Processing at Egg Breaking Facilities (RAO 270).
- Health Canada, Food Directorate. 2011. Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella Enteritidis. Int. Food Risk Anal. J., submitted.
- 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.
- Holt PS. 2003. Molting and Salmonella enterica serovar Enteritidis infection: the problem and some solutions. Poult Sci. 82:1008-1010.
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- Kinde H, Castellan DM, Kerr D, Campbell J, Breitmeyer R, Ardans A. 2005. Longitudinal monitoring of two commercial layer flocks and their environments for Salmonella enterica serovar Enteritidis and other salmonellae. Avian Dis. 49 (2):189-94.
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- 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).
- Public Health Agency of Canada (PHAC). 2009. National Notifiable Diseases On-Line. Available at: http://dsol-smed.phac-aspc.gc.ca/dsol-smed/ndis/list_e.html (Accessed April 29, 2009).
- St Louis ME, Morse DL, Potter ME, DeMelfi 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 control of salmonellosis. JAMA. 259(14):2103-7.
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10. Consultation Workbook
Health Canada's Bureau of Microbial Hazards is seeking comments on proposed recommendations to improve the microbiological quality of shell eggs. The following key groups are being invited to participate in the consultations:
- veterinary professional associations;
- agriculture professional associations;
- health professional associations;
- the food industry;
- academia/research organizations;
- consumer and community associations; and
- federal/provincial/territorial governments.
A summary of the recommendations is presented in this workbook, followed by a series of questions asking for your feedback. The consultation workbook can be completed and submitted on-line starting November 9 to December 21, 2011 inclusive. Comments from stakeholders and interested parties will be reviewed after the comment period.
10.1 Guidance for the Production of Table Eggs: Recommendations 1 to 10
- Chicken hatchery supply flocks should be free of S. Enteritidis. The means to achieve this need to be addressed, and consideration should be given to the use of harmonized methods which would result in a greater reliability of test results.
- Egg-type chicks should not be raised to be or supplied as egg layers, where likely exposure to S. Enteritidis has taken place.
- Pullets should be reared in environments separated sufficiently from broiler operations as well as other poultry and other livestock operations, so as to prevent cross-contamination.
- Pullets should be tested twice during the pullet-rearing stage. Laying flocks that are supplying shell eggs for the table market should be tested a minimum of twice per laying cycle.
- The practice of induced moulting of laying flocks should be discontinued. Any moulted laying flocks should undergo increased testing.
- All provinces and territories should use the same sampling protocol and methodology to perform environmental testing of laying flocks for S. Enteritidis. Sampling in the flock environment should comprise a variety of samples.
- When the environment of a flock tests positive for S. Enteritidis, it is recommended that the eggs from that flock be diverted for further processing, for the lifetime of that flock.
- Pullet flocks that test positive for S. Enteritidis should not be supplied to egg producers for use as laying hens.
- Laying flocks that are supplying shell eggs for the table market should participate in a HACCP-based On-Farm Food Safety program that addresses multiple potential sources of S. Enteritidis.
- Laying flocks that are moving into houses that tested positive for S. Enteritidis while being inhabited by the previous laying flock, should be vaccinated.
10.2 Post-Production Guidance for Table Eggs: Recommendations 11 to 20
- Imported shell eggs should only be sourced from foreign exporters who can certify that eggs originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all environmental test results consistently being negative for S. Enteritidis.
- The importation process for shell eggs (for both global and supplemental import permits) should allow effective traceforward investigations.
- Surplus hatching eggs should proceed to processed egg stations for pasteurization, unless the eggs originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all environmental test results consistently being negative for S. Enteritidis.
- Shell eggs being offered for sale on the table market should originate from laying hens under a HACCP-based control program with at minimum, an equivalent testing scheme for S. Enteritidis, with all environmental test results consistently being negative for S. Enteritidis.
- Only graded eggs should be permitted for sale at farmers' markets, as well as in retail environments, restaurants and foodservice institutions.
- Cracked eggs should not be offered for sale as table eggs. Cracked eggs should only be sold to:
- federally-licensed processing stations for pasteurization, or
- food processing plants operating under Good Manufacturing Practices, with the condition that the egg ingredients receive a heat treatment equivalent to pasteurization (in other words, validated for a minimum 5-log reduction of S. Enteritidis).
- All sectors involved in egg production should ensure that their processes respect the prompt refrigeration of eggs, in order to maintain the microbiological quality of eggs.
- Egg-grading stations should include in their 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.
- Eggs originating from flocks whose environments tested positive for S. Enteritidis should proceed directly to the processed egg station for pasteurization.
- Shell eggs sent to a processed egg station should be kept under refrigeration, or stored for a maximum of 6 days at storage temperatures of 20°C or less, or stored for a maximum of 2 days for temperatures between 20°C and 30°C.
10.3 Consultation Questions
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