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following complaints and in 1,368 instances infestation was confirmed
and dealt with by the rodent operatives. 100 business
premises were found to be infested with rats or mice and these
were all disinfested during the year. 24 of these were treated
by the occupiers. Regular inspections are made of premises
where food is prepared or sold and particular attention is given
to methods of prevention of rodent infestation. Corporation
owned premises including sewage works, refuse tips, depots,
school kitchens and serveries, etc., are periodically inspected
for the presence of rodents and if infested then action is taken
by the department to eradicate the pests. 10 infestations at
such premises were dealt with during the year.
The baiting of the Corporation's sewers has now been
carried out at regular six-monthly intervals since 1947 and although
the rat population was markedly reduced at the first
treatment, subsequent maintenance treatments have shown that the
method and types of poison used was only capable of reducing the
number of infested manholes recorded at each treatment to an
average of 450. This method consisted of laying unpoisoned bait
on the benching in manholes on two consecutive days in order to
attract rats to a feeding point and then following up with a
bait containing Arsenic, Antu or Zinc Phosphide on the third day.
A substance known as Warfarin, an anti blood coagulant, was
introduced in 1952 and has been used to deal with infestations
on the surface with very good results, but as this has to be laid
in sufficient quantities to be available to the rat for several
days it was found impossible to leave it down in the humid
conditions of the sewers without becoming affected with mould
growth consequently affecting its palatability. In 1956 the
introduction of two mould inhibitors, Paranytrophenol and
Dehydroacetic Acid, in a bait base of pinhead oatmeal made it
possible to use Warfarin in the sewers. A selected area of the
more heavily infested sewers, numbering 650, was prepared in
order to test the efficacy in the use of Warfarin in the sewers
and to arrive at the most economical method of applying treatments
without loss in efficiency. These manholes were treated
in the Winter of 1956/7 and in the following Summer only 60 of
the manholes in this area showed any activity. Following this
the remaining manholes in the Borough were checked and where
necessary were incorporated in the treatment at this time. The
last treatment carried out in the Winter of 1957/8 has shown
that the use of Warfarin in the sewers has been fully justified,
only 30 manholes being found to contain rat infestations.