HEALTH

NEW HAVEN DEPARTMENT OF HEALTH

Vol. XLVIII, No. 8	August, 1921

This article excerpted from pp. 2-3, 12 of the issue.

Extracts from Public Health Bulletin, No. 103, June, 1919

It is a widespread and very popular belief, that however obnoxious an animal parasite may be, it has some compensatory feature attached to its existence; that in nature's scheme of affairs it fulfills some useful purpose.

A thoughtful consideration of the rat, however, fails to reveal any redeeming feature that could justify a tolerance of this highly destructive and disease-bearing pest. Perhaps in other ages and under different sanitary conditions than now exist in civilized communities the rat served as a much needed scavenger; but changing conditions have robbed the rat of even this questionable argument for existence.

The economic losses occasioned by this animal and the menace its presence causes through its disease-bearing potentialities have aroused people to make widespread warfare against rats, but such efforts have been to a degree spasmodic and individual, rather than collective.

Any estimate of the rodent population of the United States can be nothing less than a conjecture, but a guess of one rat per person would probably be conservative. Such an estimate would be supported by the intensive studies of the United States Public Health Service in its sanitary campaigns in several large cities, in which the rodent population was calculated on trapping percentages.

Guesswork likewise enters into any computation of economic losses due to damages done by the rat, since many of them subsist throughout their lives on garbage or other refuse; but, on the other hand, the losses incurred by one rodent's depredation in a single night has amounted to many dollars.

In general, there are three varieties of rats in American cities, excluding mice: the brown rat, variously known as the "Norway" rat, barn rat, sewer rat, gray or wharf rat, is the most common species. None of these species is native to the United States. They were all imported. Some knowledge of the rat's habits is essential to intelligent effort toward its destruction. Rats are notoriously prolific. The female rat produces from three to five litters yearly, and has been known to bear young monthly, throughout the year.

Rats are nocturnal in their habits and can see better at night. The rat is a great traveler, both overland and by transportation. They are not infrequently found in freight cars, and practically nearly every ship that enters a port brings a large number of rats, unless artificial means have been carried out for destroying these undesirable stowaways. The number of rats taken from ships by fumigation and trapping has on frequent occasions amounted to several hundred.

Intensive, thorough studies of damage done by rats are lacking, but sufficient random observations are available to make it certain that the cost of maintaining rats is a big economic drain on the Nation. It has been determined that the rat will consume 50 pounds of grain in a year and will damage considerably more.

Because the rat is an animal of nocturnal habits, its depredations often pass unnoticed or are ascribed to other causes.

Rats have been the agents in transmitting bubonic plague into all parts of the world. According to authoritative records, this disease has, in recent centuries, destroyed millions of lives. Plague has not only caused an enormous loss of lives, but the measures for its control have cost many millions of dollars.

Rats are frequently infected with intestinal parasites, especially tapeworm. Trichina is also found in rats, and these rodents are probably a considerable factor in transmitting the infection among hogs, from whence it may infect men.

Of all disease-bearing parasites the rat stands supreme in the cost its presence has entailed upon mankind in toll of lives and money.

Rat destruction can be accomplished by individual effort to a limited degree, but to be successful in a large city the measures attempted must be communal in nature ie., the rat proofing of buildings. No spasmodic or individual effort will result in the desired end.

Rats can be destroyed by trapping, by poisoning, and by using natural enemies, such as certain breeds of cats and dogs. To insure the success of these measures it is necessary to curtail the rat's food supply by properly disposing of garbage and table refuse, and by preventing rats from gaining access to such food as is contained in pantries, groceries, markets, stables, etc. The municipal government will have to assist the efforts of the citizens along this line by crating and enforcing rat-proofing laws. To merely keep premises clean and free of rubbish will be of but little benefit, as Norway rats, even when abundant rubbish is available, prefer more secure covert, as that beneath floors, and within double walls and ceilings.

Much has been written about rat trapping, the pattern of trap or kind of bait, and methods of trapping; but after all has been said and done, it still remains probable that success in trapping is proportional to the attention and industry the trapper devotes to his traps and the protection of other food supplies. Two kinds of traps are generally used - the wire cage trap and the snap trap or dead fall. To obtain the best results the traps must be well attended and frequently moved from one place to another. Large cage traps, 20 inches in length, are much more effective than the smaller ones. The placing of traps is important. They should be placed wherever rats have been accustomed to come for feeding purposes and should be more or less concealed, the small snap traps by scattering dust, flour, or corn meal on or about them, and the cage trap by pieces of sacking, straw, or rubbish, leaving only the opening free.

The prerequisite of successful trapping is that no food, other than the bait, shall be available to the foraging rodents. Other things being equal, highly savored articles, such as cheese and toasted bacon, will more quickly attract rats than will food without odor; but the idea that a rat can be enticed into a trap by the employment of bait more appetizing to him than the surrounding food supply is fallacious. To the rat, food supply is a question of availability, and preference is of secondary consideration.

Generally speaking, however, it is probable that the rodent which frequents a grain house is most successfully trapped by the use of grain; and in meat markets, meat may be the best bait; or, again, rats found in green groceries, where vegetables are kept, are more easily attracted by baiting the trap with vegetables.

The destruction of rats by poison has always been more or less in favor. A preparation of arsenious acid or phosphorous, 10 per cent. in suitable base, as cheese, meal, or glucose, are the most popular poisons in use. Strychnine placed inside pieces of food, or grain impregnated by its solution, is used to some extent, as is also plaster of Paris in the proportion of I part to 2 parts of flour. This forms enteroliths and eventually kills the rodent. Poisons undoubtedly have a certain efficiency in ridding a place of rats, but whether by causing their migration or their actual destruction is somewhat difficult to determination. At best it is haphazard and uncertain. The effectiveness is always a matter of conjecture, and there is doubt as to whether the results compensate for the labor expended.

There is nothing in doubt as to the results of trapping. The employment of the natural enemies of the rat, such as dogs, cats, mongoose, or weasels, is at best only a feeble auxiliary measure, The writer has frequently seen places overrun with rats, notwithstanding the presence of the above-mentioned natural enemies. Undoubtedly some breeds of cats and dogs are better than others for rat-catching purposes, but the average domestic cat or dog is not a success in preventing rodent infestation, owing to the protection of artificial harborage afforded to the rat.

Comments

Rats have most probably been very numerous in this locality for many years and have always been regarded as a great nuisance on account of the damage done by them. It is only comparatively recently that it has become known that they are carriers of pestilential diseases and are a menace to human beings. The prevalence of rats was not appreciated by the general public until the danger was so generally advertised by the publications on rats, their habits and rat-borne diseases.

The attention of the people was not drawn to these animals as long as they were not seen. When there were many horses kept in this city and a large number of barns for their accommodation, rats were comparatively seldom seen about the houses and yards, as they could find an abundance of feed and advantageous hiding places in the barns. Since the doing away, in a large measure, with horses and the consequent disuse of barns, rats have been compelled to seek food in more conspicuous places and are often, by reason of hunger, very bold.

Garbage and exposed foods do more to attract rats than does a congenial habitation. The ordinary garbage can is not proof against rats, but is most convenient for feeding. There are several styles of garbage receptacles that set in the ground and are tightly covered, that are both sanitary and rat-proof.

The time is not far distant when a war for the eradication of the rat will be waged. Such cannot be effectively carried on by any localities, but must be at least a state wide, but better a national campaign. When the fight against this dangerous and destructive pest is begun, it must be under the guidance of an intelligent and well informed head and cannot be otherwise than costly in money and labor. In the meantime we urge each household to protect itself by the following advice of the United States Public Health Service:

ROUT THE RAT!

By starving him, through the use of ratproof receptacles for food, and covered metal garbage cans.

By depriving him of breeding places, through the abolition of planked yards and passageways.

By refusing him admission to the comfort of your buildings, through rat-proof construction, and screened basement openings.

By killing him at every opportunity.

By demanding city anti-rat ordinances and state anti-rat laws.