15 MAY 1936, Page 20


[To the Editor of TILE SPECTATOR.] SIR,--I have read with interest Mr. S. L. Bensusan's article and subsequent correspondence on this subject. It is possible that the experience which I have gained during the past sixteen years, in this country and abroad, may be of some benefit to readers who may, from time to time, have difficulty in repressing the activities of rats and mice.

During the War, when the potential danger of rats to our food supplies, very often stored in sheds which were not rat-proof, was recognised, temporary legislation ordered the destruction of the rodents and, with the coming into force of the Rats and Mice (Destruction) Act, 1919, a perma- nent measure was introduced to enforce steps to be taken to kill rats and mice. Under the Rat and Mice (Destruction) Act, 1919, the onus of destroying these rodents is placed upon the " occupier " of land, including any buildings or any other erection on the land and any cellar, sewer, drain or culvert in or under land ; and he is advised to " take such steps as may from time to time be necessary and reason- ably practicable for the destruction of rats and mice on or in any land of which he is the occupier," or for preventing rush land from becoming infested with rats or mice. In default, he is liable on summary conviction to a fine not exceeding £5, or not exceeding £20 where he has been served with a Notice under the Act requiring him to take such steps, lie." Although fifteen years have passed since the introduction of this Act it is estimated that there are no fewer than 60,000,000 rats and about half that number of mice in this country ; more than two rodents to every human being in the same area.

Rats may be sexually mature when 3-4 months old, and they can breed all the year round. The male is always ready to pair ; the female cannot be impregnated except at the period of heat," which occurs at intervals of about 10 days and lasts for only a few hours. The period of gestation is 18 days and the female is ready to be impregnated within a few hours of the birth of a litter varying from 7 to 13 rodents.

Mr. Bensusan has dealt with some of the diseases trans- mitted from the rat and the types of rodents, each with its definite characteristics, but the problem is in the extermination of the pest.

In certain States in North America regulations have been framed to ensure the freedom of buildings from rodent and insect infestations in so far as it is possible, and each owner of a building must, even before the building is completed, enter into a contract with an exterminating company, for the treatment of the premises during and after erection, and notify the local Health Board of the contract. Failure on the part of an owner to carry out these regulations would result in a prosecution.

The extermination of rodents can only be carried out effi- ciently if every possible infested area is dealt with at the one time, and with a very liberal baiting, except in the cases where hedgerows and grass banks, or haystacks, harbour rodents ; these places can be effectively treated with carbon monoxide by attaching a length of rubber tube to the exhaust pipe of a car and running the engine for a sufficient length of time to permit the permeation of gases. It is essential when baits, composed of poison such as squills, barium carbonate, phosphorus, potassium cyanide, or arsenical compounds, or strychnine preparations are used, that great care should be taken to prevent the access of human beings, or other animals, to the baits.

I have found that the best method to exterminate rats and mice in a safe and efficient manner is with a British-made virus which has the additional -advantage of killing the rodents by contact with each other. This preparation (which is known throughout the country) is guaranteed to be harmless to all life other than that of rats and mice, and does not contaminate foodstuff. Rodents die after a few days of the baiting, but, during that period, they can infect other rodents with the fatal disease. Applications of this bait must not be laid more frequently than at 14 days interval ; the first dressing must be given liberally, it will speedily be eaten, subsequent dressings will not usually be more than two applications at 14 days interval.

Another recommendation to this method of rodent exter- mination is that tLe rodents do not die under the flooring or cause a nauseous odour from decomposition after death ; virussed rodents die in the open and dry up completely, and, after all, in these times of scientific progress and bearing in mind the fact that the average individual has so little time to devote to the pastime of trapping or catching a few of the many hundreds of rodents, is it not easier to give the rat the facility of exterminating himself and also his colonies by a rodent bacteria which is fatal only to rats and mice Y—I am, Sir, yours faithfully, F. J. T. STRUGNELL. 9, Bramshill Gardens, 1V.11'. 5.