| Outbreaks of Salmonella enteritidis associated with raw
eggs continue to be common (1,2,3), despite the risk of using raw eggs being
well known. In many cases S. enteritidis is a self-limiting illness
but - particularly in very young and very old people - it can be severe
enough to require admission to hospital, become invasive, and cause death.
We asked members of the editorial board of Eurosurveillance whether
their countries have taken steps to reduce the risk of salmonellosis associated
with eggs.
We received replies from Sweden, the Netherlands, England and Wales,
France, Greece and Spain. Two approaches are described : one based on
making the poultry free from salmonella, the other on advising caterers
and consumers to cook eggs thoroughly and use pasteurised eggs for dishes
that are lightly cooked.
Swedish eggs and egg laying flocks (layers) are free of salmonella. Government
regulations, first introduced in 1961 in response to a large salmonella
epidemic in 1953, control the quality of egg laying hens, their lineage,
and their feed. The idea is that the animals at slaughter should be free
of salmonella, by preventing contamination at all parts of the production
chain, monitoring the production chain at critical control points to detect
if salmonella contamination occurs, and taking actions necessary to eliminate
the organism when salmonella contamination is detected. The grandparents
of the layers are imported and have to be certified to originate from
salmonella free parents. They are quarantined for 15 weeks, during which
time they are tested four times for salmonella. If salmonella is isolated
the chickens are destroyed. Since 1990, 90% of the layer flocks have been
tested for salmonella before slaughter as well as during the egg production
period; this became mandatory in 1994. Since 1991, only heat treated feed
has been given to chickens during rearing, and commonly during their production
period. The control of imported grandparent birds is probably the most
important factor in the prevention of salmonella contamination in Sweden
(4).
In the Netherlands a national programme to eradicate S. enteritidis
from poultry breeding flocks was implemented in March 1989 by joint efforts
of the government and poultry industry. It is hoped that this programme
will lead to the elimination of S. enteritidis from the top of
the poultry production chain to the bottom. More recently as a consequence
of the European Union zoonoses order (5), S. typhimurium has also
been included in the programme. As far as the layer breeding stock is
concerned, the control programme has been successful: no positive flocks
were found in 1996. Vertical transmission of S. enteritidis from
parent flocks to commercial layer flocks is at a minimal level, but the
S. enteritidis control programme for layer breeding flocks did
not reduce the number of commercial layer flocks infected with S. enteritidis.
These flocks were becoming infected mainly directly from the farm environment.
In July 1996, cleaning and disinfection of poultry houses followed by
a bacteriological check on hygiene before restocking became mandatory
for all commercial layer farms.
In 1988 the Government's chief medical officer in England advised that:
“people should avoid eating raw eggs or uncooked foods made from
them and that vulnerable people such as the elderly, the sick, babies,
and pregnant women should consume only eggs which have been cooked until
the white and yolk are solid” (6,7). It was recommended “that
caterers should continue to increase their use of pasteurised egg, particularly
for dishes that are not subject to further cooking prior to consumption”.
Handling and storage, the training of food handlers, improvements in the
monitoring/reporting of outbreaks of foodborne illness, and government
measures for the control of salmonella in poultry were subsequently included
in recommendations (8).
France introduced a programme for the control of S. enteritidis
throughout the poultry production chain in 1990. The elements of this
programme, called “Contrôle Officiel Hygiénique et Sanitaire”
(COHS) are as follows. Buildings and installations for poultry breeding
flocks and layer flocks, animal feed, and working conditions have to meet
strict hygiene and sanitary standards. Surveillance based on the sampling
of animals at different steps of the production chain (grandparents, parents,
and layers) and their environment is undertaken under the control of veterinary
services. If positive results occur, the animals are slaughtered and the
breeders are indemnified by the ministry of agriculture (Ministère
chargé de l'Agriculture). This system, optional until now, will
become mandatory in 1998. A branding system for eggs will enable the flocks
of origin to be easily located in the event of a foodborne outbreak and
appropriate measures to be taken with very little delay.
The ministry of agriculture issued recommendations on the use of eggs
in catering in 1989. The Bulletin Epidémiologique Hebdomadaire,
published by the ministry of health (Ministère chargé
de la Santé) makes recommendations on the use of eggs in the general
population when reports of foodborne infections are published. It recommends
in particular that vulnerable people (elderly, ill, babies, and pregnant
women) should eat eggs only if cooked until both white and yolk are solid
.
Finally, in accordance with the European Economic Community's directive
93/43 EEC on food hygiene, professionals issue guidelines on good practices.
Concerning catering for large numbers, it is recommended that eggs should
be supplied by a certified packing company, prepared in the shortest possible
time before consumption, that preparations with undercooked eggs should
be prohibited, and that the use of commercially manufactured mayonnaises
or that made from pasteurised eggs should be used. Guidelines for bakeries
and restaurants recommend the exclusive use of eggs from poultry flocks
registered with COHS.
In Greece guidelines/recommendations were issued in 1990 in response
to increasing numbers of cases of salmonellosis, particularly S. enteritidis.
The recommendations were prepared by the Public Health Division of the
Ministry of Health, the National Reference Centre for Salmonella and Shigella
of the National School of Public Health, and the Regional Salmonella Centre
of Northern Greece and issued to all local health authorities. The guidelines
recommend the use of pasteurised eggs in catering and that vulnerable
people should avoid eating raw or undercooked eggs. The general public
has been advised not to use eggs with visible cracks, only to eat well
boiled or fried (solid whole egg or yolk). No egg or egg products of any
kind should be used, unless pasteurised, for the production of food which
does not undergo any further heat treatment - for example, mayonnaise
and ice cream.
The Spanish Ministerio de Sanidad y Consumo (Ministry of Health) issued
guidelines in 1991 concerning salmonellosis and eggs, which recommended
the use of pasteurised eggs in catering. Guidelines on food hygiene for
the general population have also been issued.
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| Acknowledgements
Patrick Wall (England and Wales), Evelyne Maillot (France), Afroditi
Karaitianou-Velonaki (Greece), Lynette Wijgergangs (the Netherlands),
Salvador de Mateo (Spain), and Birgitta de Jong (Sweden).
References
1. Furtado C, Crespi S, Ward L, Wall P. Outbreak of Salmonella enteritidis
phage type 1 infection in British tourists visiting Mallorca, June 1996.
Eurosurveillance 1997; 2: 6-7.
2. Grein T, O'Flanagan D, McCarthy T, Prendergast T. An outbreak of Salmonella
enteritidis food poisoning in a psychiatric hospital in Dublin, Ireland.
Eurosurveillance 1997; 2: 84-6.
3. Outbreak of Salmonella enteritidis phage type 6 infection associated
with food items provided at a buffet meal. Commun Dis Rep CDR Rev 1997;
7: 87-90.
4. Wierup M, Engström B, Engvall A, Wahlström H. Control of
Salmonella enteritidis in Sweden. Stockholm: Swedish Animal Health Service
5. Council Directive 92/117/EEC of 17 December 1992 concerning measures
for protection against specified zoonoses and specified zoonotic agents
in animals and products of animal origin in order to prevent outbreak
of food-borne infections and intoxications. Official Journal of the
European Communities No L62/38-48, 15.3.93.
6. Department of Health. Salmonella and raw eggs. London: Department
of Health, 1988 (Press Release 88/285).
7. Department of Health. Salmonella and eggs. London: Department of Health,
1988 (Press Release 88/409).
8. Advisory Committee on the Microbiological Safety of Food. Report on
salmonella in eggs. London: HMSO. 1993.
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