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18
The danger of the introduction of Plague by means of rats was recognised
by your Medical Officer in 1901, and in that year a circular letter was sent to
the various shipowners, &c.—this pointed out that "Rats are largely
responsible for the conveyance of Plague "—and asked them to co-operate with
this Authority in certain measures of precaution which included :—-
"The careful observation of any unusual variation in the number or
"habits of rats on their vessels, and the presence of any dead rats on
"board should be noted and at once reported."
"That so fur as practicable all rats on board should be destroyed by
"competent rat-catchers and their bodies burned in the ship's furnaces, or
"by filling the holds with sulphur di-oxide gas."
"The mooring ropes when lying at foreign ports should be fitted with
"brushes, futinels, or other guards to prevent rats getting on board,"
The Dock Companies were also urged to take measures to destroy rats in
the docks, and each Sanitary Inspector received instruction to pay especial
attention, and to obtain a return of all rats destroyed in the docks and on
board vessels.
The Dock Companies readily co-operated with this Authority in regard to
the destruction of rats, and the numbers killed were reported to the Port
Sanitary Committee each month.
At this time a virus was discovered which seemed at first sight to be just
what was required to efficiently destroy rats. This consisted of a bacillus
which could be grown in quantities in suitable media, and when eaten by rats,
it was claimed would infect them with a fatal disease which was communicable
to other rats, so that an epidemic would break out amongst the rats and cause
their complete destruction.
Some of this virus was obtained from the discoverer, and it was given a fair
trial in a warehouse in one of the docks which was infected by rats, but alas !
anticipations were not realised. The virus spread on bread was eaten readily
by the rats, but there was no observable mortality amongst them; and the
numbers showed not the slightest sign of diminution.
Professor Klein was consulted, and the virus made more virulent; guinea
pigs were killed by it, and their bodies when placed in the warehouse were
devoured by the rats, but the results were absolutely negative. It was,
therefore, decided to rely on the ratcatcher with his traps and chemical poison.
Instructions were given in 1905, that vessels from certain ports should be
specially visited each day during the discharge of cargo, and the Sanitary
Inspector should satisfy himself by inquiry and personal observation, that no
dead rats had been discovered on board.