London's Pulse: Medical Officer of Health reports 1848-1972
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Hints from the Health Department. Leaflet from the archive of the Society of Medical Officers of Health. Credit: Wellcome Collection, London
City of London 1956
[Report of the Medical Officer of Health for Port of London]
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(b) The generation of hydrocyanic acid gas by various methods. For the destruction of
rats a concentration of HCN at the rate of 2-ozs. per 1,000 cubic feet of space is required
with a minimum of two hours contact.
(c) "1080" and "Warfarin". The employment of "1080" has been used regularly throughout
the docks for some time with highly satisfactory results both on shore and in ships. An
increasing number of ships have been deratted by this method in preference to the use of
cyanide, resulting in a considerable saving of time and cost to the shipowner.
Although satisfactory results have been obtained from the use of "Warfarin" a suitable bait
has yet to be found, particularly in granaries, with which to mix the poison, so that rats will
take it continuously in preference to grain and other forms of cereal on which they are normally
feeding.
(d) Trapping. Trapping is seldom employed save for the destruction of isolated rats which
have escaped a major poisoning operation or which have not yet established themselves.
The following are the names of the firms approved for carrying out the deratting of ships:—
Messrs. Associated Fumigators Ltd. Messrs. Fumigation Services Ltd.
Messrs. London Fumigation Co. Ltd. Messrs. Ridpests Ltd.
Messrs. Scientex (Southern) Ltd. Messrs. Insecta Laboratories Ltd.
RODENT CONTROL
Arising out of a Resolution of your Worshipful Committed regarding the advisability of printing
in the Monthly Reports comparative figures of the numbers of rodents (rats and mice) destroyed,
both on vessels and on shore premises, it was suggested that instead of quoting the comparable
figures for the previous year, an average figure for a number of preceding years should be quoted.
Acting upon this suggestion your Medical Officer investigated the figures relating to the
destruction of rodents during the past five years (1951-1955) inclusive, with the following results
1. On Vessels
| black rats | brown rats | total | rats examined | rats infected with plague | mice | |
|---|---|---|---|---|---|---|
| 1951 | 2,728 | 1 | 2,729 | Nil. | Nil. | 603 |
| 1952 | 2,240 | 27 | 2,267 | Nil. | Nil. | 958 |
| 1953 | 1,869 | 4 | 1,873 | 8 | Nil. | 343 |
| 1954 | 2.305 | 4 | 2,309 | 20 | Nil. | 808 |
| 1955 | 3,188 | 17 | 3,205 | 39 | Nil. | 803 |
| Totals | 12,330 | 53 | 12,383 | 67 | Nil. | 3,515 |
Giving a weekly average (5 x 52 — 260 weeks) as follows:—
47.4 0.2 47.6 0.3 Nil. 13.5
2. On shore
| black rats | brown rats | total | rats examined | rats infected with plague | mice | |
|---|---|---|---|---|---|---|
| 1951 | 3,220 | 3,862 | 7,082 | Nil. | Nil. | 2,221 |
| 1952 | 1,626 | 3,381 | 5,007 | Nil. | Nil. | 2,151 |
| 1953 | 1,327 | 2,556 | 3,883 | 1 | Nil. | 3,564 |
| 1954 | 1,462 | 1,813 | 3,275 | 1 | Nil. | 4,327 |
| 1955 | 1,045 | 1,467 | 2,512 | 4 | Nil. | 3,836 |
| Totals | 8,680 | 13,079 | 21,759 | 6 | Nil. | 16,099 |
Giving a weekly average (5 x 52 — 260 weeks) as follows:—
33.4 50.3 83.7 .002 Nil. 61.9
An investigation of this nature produced two very interesting features, namely:—
(i) The numbers of rodents destroyed "On vessels" does not afford any criterion since they
are subject to so many features such as (a) the areas from which the vessels arrive, (b) the nature
of the cargoes carried, i.e., whether rat or mice attractive and (c) the number of such vessels
requiring deratting.
(ii) The numbers of rodents destroyed 'On shore' however, are significant and indicate that
following the day by day rat repressive measures taken by your Inspectors and Rodent Staff and
the intelligent use of the most up-to-date rodenticides, the rat population has been greatly reduced.
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