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pumped out. Such was the vigilance and prompt action of the
Council's Officers during the year that no complaints or evidence
of nuisance from mosquitoes came to the notice of the Public
Health Department.
Rodent Control
Early in the year a communication was received from the
Ministry of Agriculture, Fisheries and Food requesting a meeting
with the appropriate Officers of this Council to review briefly
the present system of sewer treatment; to suggest that the use
of Warfarin blocks should be discontinued, and to submit detailed
recommendations for future treatments. At this meeting the
Ministry's representatives put forward an alternative scheme
recommending the use of a new substance (paranitrophenol) as
a preservative for rat baits in sewers.
It was pointed out that Camberwell had been carrying out
experiments with Warfarin block at the Ministry's request for
some considerable time and that the results obtained had been
most encouraging and justified the continued use of this method.
It was also indicated that the method now suggested by the
Ministry was in the nature of a further experiment and was
likely to prove more costly. It was therefore agreed that an
alternative scheme should be submitted to the Ministry with
estimated costs of both methods for purposes of comparison.
The cost of the method recommended by the Ministry was
estimated at £1,300 annually as compared with £615 a year for
the alternative scheme submitted by the Rodent Officer which
was as follows:
"All sewer manholes to be treated four times a year with
¾ib. block bait containing Warfarin, each treatment being
spread over five weeks."
It was pointed out that this method of treating sewers for
rat infestation would be most economical and would provide
maximum cover throughout the year with only four visits to
each manhole. It would ensure that bait is available in the
sewers to cope with residual rat populations, movement of rats
in sewers and re-invasion. It would also provide a more easily
controlled method of working and would comply with the
Ministry's recommendation that the same baiting material
should be used for both surface and sewer treatments.
Following further representations the Ministry subsequently
approved the scheme suggested by this Authority's Officers for
a trial period of one year. This scheme was put into operation
in July 1957. Details of the work of the Rodent Control section
appear in the statistical appendix to this report.