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RAT REPRESSION.
Rat repression has been carried out under the Rats and Mice (Destruction) Act, 1919, and in
compliance with the terms of the general " Direction " issued to all Local Authorities by the Minister
of Food, in exercise of his powers by virtue of the Infestation Order, S.R. & 0.680, 1943.
The staff engaged on the work during the year comprised a Chief Rodent Officer, and 5 assistants,
and their main duty was operational. When not engaged on operations they were employed surveying
defined areas for the purpose of instituting collective action.
The policy has again been to seek the co-operation of occupiers and owners of premises rather
than the forceful method of serving Statutory Notices under the Act, and the response has justified
this procedure. In the few instances where difficulty was encountered with occupiers, this was quickly
surmounted by explanation of responsibilities under the Act and the benefit to be gained by collective
action.
On the operational side of the problem, the work was divided into two parts, Sewer maintenance
treatment, and overground treatment.
In assessing the value of Sewer treatment, the effect on surface infestations by the common rat
must be considered, as there is undoubtedly a connection between the two.
For example, rats poisoned in the sewers have been found dead in untreated surface premises,
and one large area which was the subject of block treatment, was subsequently found to be less
infested than expected. It was ascertained from occupiers and maintenance staff that there had been
a noticeable decrease of the rat population over the past 18 months, and it is reasonable to assume
that this condition is in some measure attributable to the periodical treatment of the sewers.
Two maintenance treatments were carried out in the past year, and the following figures indicate
the results obtained.
Of 427 entrances baited during the initial treatment in December, 1943, 355 entrances or 77 per
cent. were found to be infested. The estimated kill was 3,290 rats. Subsequently the Director of the
Infestation Branch, Ministry of Food. advised the City and the Metropolitan Boroughs to conduct
periodical maintenance treatments at intervals of six months.
The first of these maintenance treatments was applied in January, 1945. 267 entrances or 64 per
cent. of the total number were found to be infested, and the estimated kill was 3,096 rats. The second
treatment conducted in June showed 165 entrances or 39 per cent. infested, a reduction of 38 per cent.
from the original infestation and the estimated kill was 1,822 rats.
Unfortunately the work on the sewers does not affect Ship (Black) rat infestation above ground,
and 80 per cent. of infestations treated were of this character.
On the Survey side of the work, 2,457 premises were inspected and of this number 330 received
treatment. 275 premises received one course of treatment during the year, 39 premises received
two courses and 16 were the subject of three or more at intervals, making a total of 417.
This entailed 5,298 revisits for operational purposes and 11,321 initial baiting points were selected.
Altogether 60,444 pre-baits were put down, and 7,926 poison baits laid.
These measures resulted in an estimated kill of 10,038 rats, and of this number 1,410 bodies
were recovered. The latter number does not include any subsequently found by occupiers when
harbourage was removed.
Trapping, as a secondary control measure, was the means of destroying 217 rats, giving a total
of 1,627 bodies actually taken from premises.
The subsequent absence of live rats from premises rather than the estimated kill or the number
of bodies found, is the best indication of the efficacy of the work.
Where practicable, structural and incidental proofing was advised, but under present conditions
the amount of structural rat-proofing that can be carried out is very limited.
The terms of the General Direction issued under the Infestation Order of the Ministry of Food
have been complied with as far as practicable, having regard to conditions in the City, and the
operation staff have maintained a keen and intelligent interest in their work.
I have the honour to be,
Gentlemen,
Your obedient Servant,
CHAS. F. WHITE,
Medical Officer of Health,
City of London.