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The extra day for pre-baiting was involved as a heavy rain storm on the 31st May washed away
a large number of the pre-baits already laid.
The number of manholes baited was 270 out of a total of 289. Pre-bait " takes " were heavy,
no fewer than 237 of the manholes baited showed " takes," whilst 123 showed complete " takes,"
on one or more of the pre-baiting days.
Infestation of the Borough is still most heavy in the Southern area, which is a more densely
populated portion. The estimated kill from the calculations of poison bait taken was 1,550 which
shows a considerable reduction on the figure for the previous treatment in 1947, which was 2,615.
This, however, must not be taken to indicate a lesser infestation of the sewers, as pre-bait" takes "
give a more accurate indication of the density and spread of the infestation.
A second sewer maintenance treatment was carried out during the period 6th to 9th December,,
inclusive, and in this instance the treatment consisted of :—
Pre-baiting 2 days—December 6th and 7th.
Poison baiting 1 day—December 8th.
Check of poison bait 1 day—December 9th.
The takes of pre-bait were again heavy and showed a wide spread infestation of the sewers particularly
in the southern part of the Borough.
The estimated kill calculated on the amount of poison bait taken was 1,030.
The takes of poison bait from examination on December 9th were poor ; in many manholes,,
which had shown clear takes of pre-bait on the preceding days, there were no takes whatever of the
poison bait.
The weather of December 8/9th was rather rainy and it is possible that a number of rats were
prevented by fast running sewers from reaching the baiting points during that night.
Sewer treatments serve a most useful purpose in killing rats before they can cause nuisance to
householders by surface infestation. At the same time the present six monthly treatments will not
secure the complete disinfestation of the sewers that was initially hoped for when the treatment of
sewers commenced, but there is no doubt that they exercise a valuable control by preventing an excessive
population ot these pests.
The following charts show the infestation of the Borough Council sewers for the year 1948, based
upon the takes of the pre-baits laid during the two sewer treatments.
The degree of infestation shown upon the charts is as follows
Heavy Infestation—Good and Clear takes of
Pre-Bait.
Light Infestation -Small takes of Pre-Bait.
Area Apparently Clear—No Pre-Bait takes from
manholes in area.
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