London's Pulse: Medical Officer of Health reports 1848-1972

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City of London 1958

[Report of the Medical Officer of Health for Port of London]

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Any dead rats are immediately sent to the Central Public Health Laboratory at Colindale for
examination for bacillus pestis, each rat being accompanied by a label on which is given precise
information as to where the rat was found in order to arrive at a focus of infection should the
examination prove positive. The information,is, of course, far more vital when the rat has been
found ashore than when found on board a ship.
In the event of a positive result the "additional measures" referred to above would be put
into operation — the discharge of the cargo would be promptly stopped and arrangements made for
the vessel to be fumigated throughout with hydrogen cyanide, with the cargo in situ, the vessel
being moved to an approved mooring.
Following the initial fumigation and collection of dead rats resulting therefrom further
samples of such rats would be submitted for examination and the discharge of cargo would be
permitted under observation. The destination of the cargo would be forwarded to the Medical
Officer of Health of the district to which it was proceeding, together with an explanatory note.
If any of the cargo had already been discharged overside into lighters before the discovery of
plague infection, the lighters would be fumigated immediately.
On completion of the discharge of cargo from the vessel a second fumigation would be
carried out, again using hydrogen cyanide, to destroy the residual rat population, if any.
SECTION XII—Measures against rodents in ships from foreign ports
(1) Procedure for inspection of ships for rats.
The Port Health Authority employs fifteen Rodent Operatives working in conjunction with and
under the supervision of the Port Health Inspectors.
The Rodent Operative's first duty is the examination of ships in his area which are due for
inspection under Article 19 of the Public Health (Ships) Regulations, 1952, relating to the granting
of Deratting and Deratting Exemption Certificates.
His second duty is to visit all ships arriving in his district, to search for evidence of rats,
paying particular attention to vessels which have arrived from plague infected ports and to visit
such vessels during the discharge of cargo.
The Rodent Operative's third duty is the examination of shore premises for signs of rat infestation
paying particular attention to premises adjoining the berths of vessels from plague infected
Some seventeen years ago the Port Health Authority instituted a Rodent Control Scheme in
all docks and premises of the Port of London Authority on behalf of that Authority and in the
premises of the tenants of the Authority on behalf of the occupiers.
(2) Arrangements for the bacteriological examination of rodents, with special reference to
rodent plague , including the number of rodents sent for examination during the year.
As described in Section XI above, all rats for examination for plague, either by post mortem
and subsequently, if necessary, by bacteriological examination, are promptly sent to the Central
Public Health Laboratory at Colindale.
The bodies are placed in polythene bags which in turn are placed inside metal boxes, sealed
and labelled so that there is no risk of the escape of any rat fleas during their transit to the
Laboratory. The boxes are, of course, delivered by hand.
The rat population of the Port is now so small and is under such strict control that it can be
said to be almost certain that the arrival of a plague infected rat, even should it manage to get
ashore, would be highly unlikely to have any serious significance. In other words, an epizootic
could not be introduced into the Port for the simple reason that there are insufficient rats to
enable the spread of infection. Nevertheless, seventy-one rats were sent to the Laboratory and
were examined for plague with negative results.
(3) Arrangements in the district for deratting ships, the methods used, and if done by a commercial
contractor, the name of the contractor.
(a) The burning of sulphur at the rate of 3-lbs. per 1,000 cubic feet of space for a period of
not less than six hours.
(b) The generation of hydrocyanic acid gas by various methods. For the destruction of rats
a concentration of HCN at the rate of 2-ozs. per 1,000 cubic feet of space is required
with a minimum of two hours contact.

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