THE DISASTROUS RAT
By S. L. BENSUSAN
IT is matter for surprise that while experts estimate the damage done by the broWn rat in England and ' Wales at £1 per head per annum of the population, reltrences to rat infestation, whether made in the House of Commons or at Rural District Council meetings, arouse little more than laughter. This is very disquieting, because as scientific investigation proceeds to study the causes of certain epidemics, it tends steadily to refer More and more of them to the rat.
Of late the Weil's disease popularly known as infective jaundice has been traced to rats ; this trouble accounted for the closing down of a coal-mine in Scotland a few years ago, because the miners in considerable numbers were contracting the complaint. Twenty years ago the Corpora- tion of the City of London made a grant to Professor Foulerton to investigate in the Valley of the Wye the evidence connecting Well's disease with rats. For some time past the infection due to the spirochaete ichterogenes has been known in Germany, and considerable research work has been carried out on it in Japan. The virus reaches rats through abrasions in the skin and is readily contracted by human beings. Bathing-pools to which rats can gain access are a source of grave danger. Only a few years have passed since some of the frequenters of a well- known pool in Holland developed infective jaundice ; it was found that the area round the water was infested by rats ; they were destroyed and the infection ceased.
Last year in London a sewerman contracted Weil's disease in the course of his work, and the attack proving fatal, the widoW received an award under the Workmen's Compensation Act. Cases of infective jaundice have been reported as near to London as Hertfordshire and as far away as Shropshire. At Newcastle last month a colliery shifter claimed and received compensation following alleged infection from rats ; it was proved that the seam in which he worked was wet and rat-infested, and that one of his mates had died from infective jaundice. During the investigation it was shown that ten other cases had occurred between 1933 and 1934 ; some had been treated at the Infirmary in Newcastle. Experiments by a pathologist at 'the Sunderland Infirmary showed that virus from a rat killed a guinea-pig in eleven 'days, and blood tests from ten men working in the coal - mine showed positive results in nine cases. The e diseas, apparently is carried by a parasite which lodges in the kidney of rats, but human beings can also be carriers. The bacteriologist at the Wellcome Bureau of Scientific Research in London, Major H. C. Brown, who is regarded as an expert on Weil's disease, says that about one-third of the rats in the British Isles harbour the parasite, and that anybody bathing in rat-infested waters is liable to get infection through the mouth.
In connexion with this charge against the brown rat it is worth remarking that further and other serious charges have been established. Rats act as primary host of the tapeworm, which is often conveyed to' the pig, and from the pig to the' human, causing trichinosis. They spread equine influenza, mange, ringworm and distemper ; they are beginning to be •'recognised as carriers of tuberculosis from farm to farm. When the late Sir Arthur Shipley, Master of Christ's College, Cambridge, declared in his book Some Minor Horrors that the rat was a carrier of foot-and-mouth disease, his statement was regarded as unfounded; indeed several men of science who discussed the question with the writer dismissed it as not worth consideration. Since then the belief has been fully justified. Experiments in Denmark, apart from those conducted in this country, have shown that rats disperse the virus of "foot-and- mouth " and that before a farm on which an outbreak has occurred is disinfected, it is absolutely necessary to exterminate the rats. So much for rattus norvegicus, but his work as a disseminator of disease and con- taininator of food does not tell the full tale of the nation's trouble. In the past thirty years, since concrete has been so freely used in building,, the brown rat has been oreatly discouraged in the City of London and the black (alexandrine) rat has taken his place. Experts say that while there were no alexandrine rats in England thirty years ago, today the population of black to brown in the City of London is as ten to one. The black or alexandrine rat (rattus alexandrinus) is a far more pleasant animal than his brown cousin. He is cleaner, friendly, lives in the house-tops instead of the cellars, but unhappily keeps bad company, acting as host of the plague flea—xenopsylla cheopsis—and was certainly responsible for the great plague of London in 1665 and 1666, and possibly for the Black Death which devastated Europe some centuries earlier. .
Bubonic plague has certain centres in which it is endemic and from which it spreads periodically. The East and Western Himalayas, the Altai Mountains, the country round Lake Tana in Abyssinia and certain parts of the highlands of Brazil are centres; from them the disease always tends to move westward. It is checked by a system of sanitary cordons, but today bubonic plague is latent in Persia, Asia Minor, parts of European Russia and South Eastern Europe. The Metropolis has long been saved from trouble by the extraordinary vigilance of the Port of London Authority, but it may be remarked that black rats carrying plague fleas did break the cordon at another port —Liverpool—not long ago, There two rats infected with bubonic plague were found—one in a grain rare- house. The facts were stated in The Timex of January 21st. If they could penetrate London, the fleas would find au infinite number of black rats waiting to receive them.
We have in this country a Rats and Mice (Destruction) Act which is nearly a dead letter. . Local Authorities will not be troubled to administer it. Sonic County Councils suggest that they cannot afford the services of whole -time Rat Officers. It follows that the rat, whose rate of increase is astonishing, is costing this country an incredible sum of money every year. and meanwhile exposing citizens to the risk of deadly diseases.
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