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Plague being primarily a disease of rats all vessels are inspected immediately on arrival at
their berths in the docks and river for the presence of any mortality among the rats on board which
is not attributable to any known cause, such as trapping, poisoning, etc.
Incidentally one of the "Health Questions" on page I of the "Maritime Declaration of Health"
requires the Master to answer "Yes or No" to the question "Has plague occurred or been suspected
amongst the rats or mice on board during the voyage, or has there been an abnormal
mortality among them?"
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
To undertake their responsibilities, the Port Health authority employs a competent and
experienced team of sixteen Rodent Inspectors, under the supervision of the Port Health Inspectors,
who exercise control measures on all ships within the Port as well as the shore premises within
the docks.
Procedure for inspection of ships for rats
All ships are inspected on arrival at the dock quay or river wharf for evidence of rodents,
particularly those ships arriving from ports that are or suspected of being infected with plague.
To this end, it is customary to attend all ships in order of priority as soon as practicable after
arrival at the berth and, if possible, before any disturbance of cargo has taken place and so gain
more conclusive evidence of rodent activity or other relevant factors, including the presence of
dead or moribund specimens. The latter discoveries may be due to diseases or the result of a
system of continuous treatment to eradicate rodents while the ship remains in service, a system
growing in popularity for ships that acquire recurring infestations from vulnerable trade routes.
The usual method of continuous control treatment involves providing fixed poison baiting
points in the cargo spaces and the peak storerooms. The bait usually comprises some form of
cereal base and an anticoagulant admixture. These baits must, of course, be attractive at all
times and to avoid moulds in humid conditions, a fungicide is added to the prepared baits. In
consequence of this treatment it is possible to discover dead rodents in the spaces when the
ship reaches port, and specific enquiries must be made by the Port Health Inspectors concerning
the dead rodents in order to establish that there is no disease connected with the mortality. It is
customary to be suspicious in such circumstances and to submit retrieved specimens for bacteriological
examination.
Arrangements for the bacteriological examination of rodents, with special reference to rodent
plague, including the number of rodents sent for examination during the year.
All rats for examination are 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 whilst taken by hand to the Laboratory.
The introduction of an epizootic into the Port is, nowadays, very slight owing to the rat
population being so small and under such strict control that the arrival of a plague infected rat,
even should it manage to get ashore, would be highly unlikely to have any serious significance.
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