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RODENT CONTROL IN SEWERS.
Between 1943 and 1954 Rodent Control in Sewers was attempted with two
treatments a year, using Zinc Phosphide or Arsenous Oxide. This method was
considered to be adequate by the Pest Division of the Ministry of Agriculture
Fisheries and Food, but an examination of the results showed that over a
number of years the rat population in the sewers appeared to be static.
From 1954 treatments were increased to three a year This showed some
improvement which may have been related to the change of bait to one including
prepared "Warfarin". With this low level of treatment it appeared
that the rat population was able to regain its natural level between treatments.
In 1961 an experiment was begun using Sodium Fluoracetamide (1081)
applied with six treatments in the year. The basis of the experiment was that
a rat matures and is capable of reproduction at about two months and it was
thought that if the rats could be killed before reaching maturity this was
likely to be the most satisfactory way of reducing their numbers.
The results are highly encouraging and it is now reported that several
sections of the sewerage system have been freed of rats and have remained
free.
Table A shows the variation in results over a period of years and
Table B shows the distribution of results over the borough.

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