View report page

During the year there has been further evidence that mice infestations are showing
signs of increased resistance to treatment. Considerable quantities of Warfarin bait
have, in a number of premises, been taken with remarkedly little reduction in the mice
population. This is in line with the information reaching the Central Government
Department. The situation in each case required persistence and change of bait. Alpha
chloralose was used as an alternative poison where conditions permitted, but this poison
is largely ineffective in centrally heated premises. A clearance was ultimately achieved
but the time expended was greater than for an equivalent rat infestation and accounts
in part for the higher number of visits paid.
134 contracts ranging from 1 to 12 months were agreed in 1969 for rodent control
work in non-domestic premises. This figure is only slightly below that for 1968.
Graphing of monthly confirmed incidents of rat infestations over the past 3 years
has revealed an interesting similarity of seasonal variation. As the graph below shows
during 1969, 1968 and rather less markedly in 1967 there was a peak of rodent activity
reached at the end of May and a low during October and November each year.
It would be interesting to know if this pattern is general in other areas. There is
no clear indication why May should be so strikingly prominent for rat activity. Biological
and breeding factors may offer some explanations and it is reasonable to suspect
that increased human outside activity in the improved weather may give rise to a greater
awareness of the presence of rats.
86