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and in 1 case the offending article of food was not proved. The
source of the infection might have been from an animal.
(i) The meat eaten may have been derived from an animal
infected with the organism. (In this case it is assumed
that the gammon was the first infected article of food.)
(ii) The meat, originally sound, may have been infected with
the organisms derived from animals (such as rats or mice)
either suffering from the disease or acting as carriers,
either at the place of origin, the wholesaler's, or Mr. A.'s
premises.
The infection, alternatively, might have been from a human
source:—
(i) A person suffering or recovering from the disease.
(ii) A passive carrier.
From the investigations made in this outbreak, it appeared
that the outbreak was due to the gammon being infected with
the B. enteritidis Gaertner, the breakfast sausage and corned beef
being infected secondarily from infected knives or hands.
It is impossible to say with any certainty by what means the
gammon became specifically infected. If the original pig was
diseased it would have been infected in its country of origin. On
the other hand, if the meat was originally sound, it might have
been infected in its country of origin, on the wholesaler's premises,
in transit, or in Mr. A.'s shop. No evidence of this could be
obtained. No rats had been found on the wholesaler's premises
for some years ; mice had occasionally been found, but not in
such numbers as suggested any undue infestation. The peameal
used for dusting the bacon gave negative bacteriological findings.
It appeared unlikely that the gammon was derived from
a diseased animal, for if this had been the case one would have
expected other outbreaks of food poisoning to have been reported
in London or elsewhere from the distribution of the remainder of
the infected pig. The fact that the interior of one uncooked gammon
was found to be free from infection, and that all the uncooked
gammons were found to be infected on the exterior, leads one to
the conclusion that the infection of the gammons in question
might have been a surface one.