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In case one should think that milk is no longer a likely vehicle of infection, it is salutory to
note that there were five outbreaks of food poisoning caused by unpasteurized milk in 1963. The
Annual Report of the Chief Medical Officer of the Ministry of Health reports three outbreaks12 so
caused and the Public Health Laboratory Service five outbreaks13. One led to an outbreak of
twenty eight cases of Salm. heidelberg14. There were about 40 cases of Salm. typhi-murium from
two of the other milk outbreaks. Bakery products featured in two other outbreaks of food poisoning,
cream cakes being the peccant food. One of these outbreaks involved some 150 persons. In
both a human carrier was the most probable source of infection.
Pork meat and processed pork meat led to food poisoning outbreaks around Leicester, pointing
to the pig as the animal reservoir of infection. Salm. brandenberg isolated from the cases was
found in pig carcases from lairages in the meat factory and its products as well as food handlers.
It is most interesting to note that in 126 outbreaks caused by food, 110 of these were meat products,
and of these 84 per cent were made-up or processed meats such as pre-cooked cold or reheated
meat, or meat pies made with pre-cooked meat.
7. Risk in particular that associated with Canned Foods
To complete the picture for 1963 as far as food poisoning was concerned, canned meats were
suspect in only two outbreaks; of these one was Salm. derby in which sliced luncheon meat was
suspect, and the other canned chicken which had been contaminated with staphylococci by an
infected hand. In another outbreak canned fish was suspect but no causal organism was discovered.
At the conference earlier this year on the Safety of Canned Foods, Dr. J.M. Ross gave a
review of problems in epidemiology and administration including a resume of some outbreaks of
food poisoning and typhoid fever due to canned meats, especially corned beef and inevitably of
S. American origin as the greater part of the supply comes from Argentina. One may add to this
list another incident. In 1955 a 6 lb can of corned beef from South America caused an outbreak
of salmonella food poisoning, and in fact in that year there were eight outbreaks associated with
canned meat, two of which were connected with freshly opened cans15.
There were the 1957 outbreaks of staphylococcal food poisoning associated with canned peas
reported in this resume, when n one considers the infection of canned food by typhoid fever following
the Crowthorne outbreak from the consumption of corned beef causing two deaths amongst
42 cases in 194916. The unique incident occurred in 1953 in which typhoid fever was actually
isolated from a can of imported cream. The cream was so sour and many cans of the batch were in
poor condition. 17 per cent of the cans examined having living bacteria though the cream was
supposed to be sterilized. Fortunately the state of the cream was such that few partook of the
contents so that only one symptomless excreter of typhoid was found. The factory concerned was
using well water which was polluted by a nearby stream17.
In the report of an outbreak of typhoid fever in Glasgow in 1942 where the suspected source
of infection was thought to be a butcher's shop, Peters and Clutterback predicted 'a meat outbreak
of this nature is a comparatively new occurrence, but with the increasing distribution of
canned meat it is not unlikely that such outbreaks may increase." They suggested that corned
beef and pressed beef and other canned meats might be contaminated after removal from the can.
We now know that canned meat can be and may have been contaminated during processing before
the can is opened18. This leads to the consideration of:
8. Risks of infection with reference to the Canning Process itself
It is interesting to note that the impetus which led to canning as a method for the preservation
of food came in the crisis of war. The acute shortage of food in 1795 during the Revolution
when France was at war with hostile nations led to the introduction of this process. The
French Government, faced with the problem, offered a prize for a method of preserving food that
would help in the maintenance of supplies for distribution to the military and civilian population
Nicholas Appert observed that adequate heating of food in a sealed container prevented spoilage
of the food though he did not know the reason why. His experiments led him to the conclusion
that cleanliness in the preparation of food, adequate heat treatment and sealing in an air-tight
container prevented spoilage. In spite of many modern advances in technicological science,
Appert's principles still are fundamental. The, big risk that has come to light through the evidence
available from recent outbreaks is the occurrence of a microleakage of cans. In other words, cans
thought to be air-tight in some instances are not really so. It was always realized from the manner
of construction of cans and the methods of sealing that there must be a possibility of defects at
the seams or ends or as a consequence of the sealing or closing process being at fault subsequent
to the filling of the cans. Attention has now been drawn in particular to tiny leaks which may
occur as a result of the varying pressures inside and outside the can due to changes in temperature
and pressure during the canning process. There is in addition the abuse of cans by knocking
and bumping in the manipulation of the cans subsequent to being filled and sealed. This occurs
in their automatic conveyance or handling while being cooled, cleansed, labelled and packed.
While preparing this paper I happened to be reading C.A. Coulson's book Science, Technology
and The Christian (Wyvern Books 1964), and at page 25 I came across the following:
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