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RODENT CONTROL MEASURES CARRIED OUT ON LIGHTERS
It is gratifying to report that in spite of some staffing difficulties the rodent control measures
on Lighters have been carried out successfully for another year.
The ratio of lighters that needed deratting has been maintained at a very low level i.e. 1.5
per cent of the total number inspected as compared with 2.3 per cent in 1964. The average number
of rats recovered per lighter deratted has however increased from 4 to 5.4.
There has been an increase in the number of lighters recorded with a negligible degree of old
evidence. This is attributed to the fact that although a lighter is usually swept up after fumigation
and so far as practicable is clean, because of its construction, at the end compartments where
angle bar is more freely used, there are places where old evidence of rats accumulates and such
places do not normally get cleaned as a routine after a deratting operation. These observations
are now being taken-into account and recorded.
Rat proofing of lighters has continued throughout the year at the various repair yards and it
is satisfying to note that since 1959 when the Lighterage Industry was generally represented at
a lecture and discussion on rat proofing techniques, the percentage of lighters requiring deratting
treatment has decreased from 4.5 per cent to 1.6 per cent of those inspected.
The following methods of deratting have been employed throughout the year:-
Fumigants. Sulphur Dioxide gas and Methyl Bromide vapour.
Rodenticides. Sodium mono-fluoroacetate baiting. The method of treatment is determined by
the circumstances and degree of infestation at the time of inspection.
Throughout the year 904 lighters have been fumigated with Methyl Bromide, for insect control
of the cargo by the following companies:—
London Fumigation Company Limited
Rentokil Laboratories Limited
Contra-Pest Service Limited.
Butlers and Colonial Wharves Limited.
New Caledonian Wharf and Millwall Wharf.
Since the dosage required for insect control varies between twenty and thirty ounces per 1,000
cubic feet according to the specie of insect pest, with a twenty-four hour exposure period, the
aggregate effect is more than sufficient to destroy any rats present at the time of fumigation.
During the year twenty-one of the rats recovered from treated lighters were sent to the Public
Health Laboratory, Colindale for routine bacteriological examination. Pasturella pestis was NOT
isolated from any specimen.
USE OF SODIUM FLUOROACETATE (1080) & FLUOROACETIMIDE (1081)
Sodium mono-fluoroacetate — '1080' — was extensively used throughout the first six months
of the year with very satisfactory results. This poison is definitely most suited to a major
seaport with a disciplined and experienced staff and the advantages in labour saving and positive
control are features which cannot be ignored in circumstances where there is a risk of rodent
borne diseases and where rodent attractive foodstuffs abound.
A drastic change, however, has been enforced since June which can only be considered as a
retrograde decision. The Poison Rules, 1965 prohibit the sale of '1080' and '1081' other than for
use as a rodenticide in ships and sewers and, therefore, the valuable potentials of these rodenticides
has been lost as regards the open spaces and warehouses, places from which some of the
most stubborn infestations have been overcome in the past by the use of these rodenticides.
A recurring infestation on a site treated with either of these poisons is unusual, a factor
which indicates the scope of their effective application and dispenses with any idea that rodents
may become resistant to their very toxic properties.
One immediate effect of this change has been a sense of frustration to the rodent staff already
strained to the limits. Much more time will be required for each operation, more money will be
needed for baits and it remains to be seen if the high standard of control can be maintained with
the additional problems arising from the major reconstruction schemes in the Docks. Present
reports indicate that the change is unfavourable.
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