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21
V.— MEASURES AGAINST RODENTS.
These remain as described in my Report of the year 1933.
There is no doubt that Article 28 of the International Sanitary Convention, 1926,
has achieved a great reduction in the rat population in ships. The proportion of
Exemption Certificates to Deratisation Certificates is increasing, and the average
number per ship of rats killed by fumigation is decreasing. There is an increasing
interest in, and appreciation of the value of, rat-proofing both in ships and ashore,
and I think it may be claimed that the spread of Plague by sea-borne commerce has
been almost stopped. Unfortunately this does not mean that there can be any
relaxation of rat-repressive measures. Rats are adaptable and prolific, and rapidly
breed up to the limits of the rat-harbourage and the food supply. They promptly
take advantage of every circumstance which is even temporarily in their favour.
Fumigation, trapping and poisoning are but palliatives. The only treatment which
holds out any prospect of lasting relief from rat-infestation is rat-proofing both in
ships and on shore in ports. The principles of rat-proofing are perfectly simple, and
their practical application is not costly if carried out at the time ships and buildings
are constructed. This is gradually being realised by those who build and those who
operate ships, and by those responsible for the construction and maintenance of
buildings in ports, but the importance of attention to small details is not appreciated.
Efficiency in rat-proofing really depends upon care in detail, for rats can pass through
small openings, and the points they select for gnawing their way into harbourage or
from one compartment to another are just those out-of-way corners which are most
likely to escape observation, and most awkward for the men who are carrying out the
rat-prOofing to work in.

See also Appendices

RATS EXAMINED—Vessels, Docks, Quays, &c. 2,800
MICE EXAMINED—Vessels 17