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In the year 1944, the comparable figures were 320 infestations treated. This number comprised
261 major (21-200) and 39 minor infestations of rats and 13 major and 7 minor infestations
of mice. A total of 62,336 pre-baits and 8,452 poison baits were laid. These measures resulted
in an estimated kill of 11,388 rats of which 2,558 bodies were recovered. In addition, 423 rats
were destroyed by traps.
The low level of Ship (Black) rat infestation manifest in recent years has been maintained
and the 15 minor infestations of this nature subject to control measures during the year under
review was the lowest yet recorded. To illustrate further the diminished status of this species
within the City, the comparable figure recorded in 1948 was 698 rat infestations treated, comprising
668 Ship and 30 common rat infestations and of the Ship rat total 249 were in the major
classification.
In reviewing the present position of this species of infestation there are many contributory
factors. Foremost of these is the diminution of re-infestation from outside sources, the great
improvement in general hygiene, progressive demolition of old properties and redevelopment,
systematic inspection, and advance techniques of control.
The importance of hygiene in relation to rodent control, embracing effective food storage,
proper waste disposal, and the elimination of structural and incidental harbourage providing
nesting facilities must be emphasized. Rats and mice are commensal creatures, i.e. dependant
on man for their food and housing, and therefore, the maintenance of good general conditions,
whatever the usage of the property, is essential, and control measures should be regarded as
supplementary to hygiene.
The relatively low status of common rat infestation was confined to the comprehensive
redevelopment sites in their varying stages of construction. Such environments offer every
facility and in every way are conducive to this type of infestation. The temporary canteens
provided for the workmen are, in the main,well kept, but under such circumstances, inevitably
create an attraction. On the comprehensive development sites where several blocks are erected
simultaneously, it is neither reasonable nor practicable for the labour force numbering several
hundred to leave the sites of production to adjourn to the main canteen for their short tea breaks,
and in such instances the tea is taken to the men with the result that waste and unwanted food
is discarded over the entire site.
On one particular site where this nuisance was very rife, representations were made to the
contracting management, and trade union representatives, with the result that the contractors
installed, at considerable expense, replaceable paper bags on wall-mounted stands for the disposal
of unwanted waste food and containers.
All building sites were periodically inspected, and the fullest co-operation of the various
contractors was received as far as possible having regard to the conditions and labour involved.
A major contributory factor in the control of common rat is the systematic periodical treats
ments applied in the City sewers. The sewer system comprises approximately 34 miles of traversable
sewers and about 5 miles of 9 inch pipe sewers. The accessible sewers are in the main
3-4 feet in diameter but certain sections are 11 and 17 feet. The entrances providing access
number about 400 and vary in depth from 10 to 35 feet.
It is the purpose of these periodical control measures to check the build-up of the rat population
in the sewers and thereby assist in preventing infestation of surface properties from this
source via defective drainage.
During the period under review, four 'Direct' poison treatments with Fluoracetamide as the
toxic agent were applied. These were carried out in March, June, September and December
respectively and an average of 390 sewer manholes distributed over the sewer system were poison
baited. The annual overall test baiting of all available manholes, which provides an indication
of the result of the treatments was applied prior to the June control and a total of 391 manholes
were test baited. These non-poison baits, which in effect act as pre-baits were left down two
days and where on examination were found to be taken, replaced by poison bait. The test bait
result on examination was 8.9% complete 'takes'. The comparable test result in 1962 was 11.6%
and that of 1961, 17.6%.
To attempt to arrive at an estimate of the number of rats destroyed in the City sewers over
the past twenty years would be mere conjecture, but taking into account the number found dead
at the base of the manholes where the poison baits were sited, analysis of the poison bait
acceptance of the 63 controls completed and bearing in mind the limited range of vision from
the base of the manholes, a minimum estimate would be approximately 10,000.
The extensive experimental control measures with Mono Sodium Fluoracetate (1080) and
Fluoracetamide (1081) and intermediate tests conducted during the period 1950 — 1960 produced
the results it was believed could be achieved by the continuation of the 'Direct' poison method
and the use of these two highly toxic rodenticides and this technique of control is now standard
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