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(2) Contamination of pies by mice or rats. This hypothesis arose out of
the fact that a bacterial virus was in regular use at the shop for the extermination
of rats and mice. Outbreaks of illness identical in symptoms with
paratyphoid fever, and stated to have actually been this disease, have been
recorded on more than one occasion, arising out of contamination of foods
by the droppings of rats or mice suffering with intestinal illness due to
poisoning by bacterial rat virus. It was felt that here again contamination
of the pies at the shop would probably not be sufficiently massive to account
for a considerable number of cases arising simultaneously, especially as no
evidence could be obtained of the presence of mice, or of pies having been
nibbled. When, however, the manager of the shop explained that the same
bacterial virus was used at the central bakehouse and at other branch shops,
the possibility of this channel of infection had to be followed up.
(3) Contamination of pies in transit from the bakehouse to the shop.
(4) Contamination of the pies at the central bakehouse, or contamination
of some ingredient before delivery at the bakehouses. This alternative would
imply the likelihood of cases of paratyphoid fever occurring in connection
with other branch shops receiving deliveries of pies from the oentral bakehouse.
Lines of investigation into source of infection of meat pies.
It thus became necessary to ascertain the general distribution of the
branch shops served from the central bakehouse; to look into the incidence
of paratyphoid fever in the areas likely to be served by these shops, and
to investigate the processes of manufacture, and the health of the employees,
at the central bakehouse. At the same time, the procedure in regard to the
use of rat virus by the firm needed investigation. It may be added here that
meanwhile a visit had been paid to the head office of the manufacturers of
the virus. Every assistance was received from the latter, who supplied a
stock of the virus to be submitted to bacteriological and serological tests.
These tests were carried out at the laboratory of the Borough Fever Hospital,
and, by the courtesy of the Ministry of Health, samples of the virus
were also submitted to detailed examination in the Ministry's laboratory. At
the same time, a warning letter was sent to medical practitioners in the
Borough, and the Ministry of Health were notified of the position. I had
further the welcome opportunity of discussing the position in detail with the
officers of the appropriate medical department at the Ministry of Health.
I propose to summarise in sequence the main points arising out of the
various lines of enquiry set out above:—
Area served by the Bakery.—The premises belonging to the firm of
bakers consisted of two central bakehouses and the head office, situated in
Croydon; and of a considerable number of branch shops, situated partly in
Croydon, and partly in neighbouring areas. One of the two central bakehouses
was concerned solely with the baking of bread, and its staff, equipment,
supplies of flour and other requisites, and processes of manufacture
were entirely distinct and separate from that of the other central bakehouse,
which was devoted to the preparation of meat pies and of a variety of fancy
and plain cakes.
Incidence of enteric fever in the areas likely to be served by the confectioners.—The
weekly list of notifications of infectious disease in each sanitary
area supplied by the Ministry of Health groups notifications of typhoid
and paratyphoid fever together under the common heading of enteric fever.