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SECTION XII
MEASURES AGAINST RODENTS IN SHIPS FROM FOREIGN PORTS
(i) Procedure for inspection of ships for rats
The Port Health Authority employs an experienced and competent team of fifteen Technical
Assistants, who exercise control measures on all ships and shore premises within the Port area
under the supervision of the Port Health Inspectors.
The Technical Assistants first duty is to visit all ships arriving in his district as soon as
possible after arrival and search for evidence of rodents. Priority is given to ships which have
arrived from plague endemic areas. Further visits to these ships are made during the discharge
of cargo to ascertain the degree of infestation on board, if any, and to ensure that reasonable
measures are adopted to reduce the number of rodents on board to a negligible number and prevent
any rodents escaping ashore.
His second duty is the inspection of ships in his area for the specific purpose of issuing
Deratting or Deratting Exemption Certificates or Rodent Control Certificates.
His third duty is the inspection of shore premises and lighters for signs of rodent infestation.
The Port Health Authority has continued to operate a Rodent Control Scheme inaugurated
twenty-nine years ago, covering all the docks and including all the premises of the Port of
London Authority on behalf of that Authority and premises of tenants of the Authority on behalf
of the occupiers.
(ii) 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 dead rats to be examined for evidence of plague are promptly dispatched in cylindrical
aluminium containers with a screw cap to the Public Health Laboratory at County Hall.
Specimen rats are placed in polythene bags previously dusted with gammaxene powder to kill
any parasites, labelled and placed inside the cylinder for delivery by hand. During the year
forty-two rats were sent to the Laboratory at County Hall and were examined for plague with
negative results.
(iii) 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 minimum
period of 6 hours. This method is seldom used now in the Port of London.
(b) The generation of hydrocyanic acid gas by various methods. For the destruction of rats a
minimum concentration of H.C.N. at the rate of 2 ozs per 1,000 cubic feet of space is
required with a minimum of two hours exposure.
(c) Sodium-fluoroacetate ("1080") and "Warfarin" The employment of "1080" as a rodenticide
has been regularly used throughout the docks for some time with highly satisfactory
results. The prohibition on the use of "1080" and "1081" (Sodium Fluoroacetamide)
except in ships and sewers, which was imposed in June 1965 was amended during the year
to permit their use also in enclosed dock premises. A substantial number of ships have
been deratted by "1080" in preference to the use of cyanide resulting in a considerable
saving of time and cost to the ship owner.
(d) Trapping. This method is seldom used except as an expedient to eliminate isolated rats
and/or to secure specimens for the laboratory.
(e) Methyl Bromide
Methyl bromide is a gas at ordinary temperatures but can be liquefied by pressure, and
it is in the liquid form in the cylinders in which it is usually distributed.
The gas is heavier than air, consequently heavy concentrations are often found at floor
level in the early stages of a treatment. However, the gas is not difficult to disperse
after an operation.
Apart from this density effect, the gas has greater powers of penetration than most
other fumigants in common use and this applies not only to penetration into commodities
but also through walls and sealing materials. A high standard of maintenance and sealing
is necessary in rooms to be used for fumigations using methyl bromide.
The penetration powers of methyl bromide, the absence of smell, the lack of immediate
symptoms of poisoning and the long term effect of poisoning, make it essential that
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