Part 16

Skunks usually hunt by night, and hence poultry properly housed is safe from them. The larger skunks do not climb, and can capture only fowls that roost on the ground. Indeed, so few skunks ever learn to kill poultry that there is no good reason for warfare on the skunk family. Besides destroying mice and rats, the animals are invaluable as consumers of noxious insects, especially cutworms, army worms, white grubs, May beetles, grasshoppers, crickets, and sphinx moths.

WEASELS.

Weasels are good ratters and mousers. Several of our species come about buildings, and often perform excellent service in destroying rats and mice. They are more likely than the skunk to attack poultry, for they can enter the poultry house through smaller openings. At times weasels seem to kill for the mere love of killing, and while occasionally this trait makes them formidable in the poultry house, it also renders them more efficient as destroyers of rodents. A small weasel can follow a rat into all its retreats, and will soon clear a stackyard or shed of all rodents.

Our largest weasel, the black-footed ferret (_Putorius nigripes_), occasionally deserts its wild haunts on the plains and comes about buildings in search of rats and mice. In 1905, while the writer was at Hays, Kans., one of these ferrets took up its quarters under a board sidewalk in the business part of the village. The squealing of the rats it killed was often heard.

As regards the destruction of poultry by weasels, the same care necessary to exclude the rat from a poultry house will keep out the weasel also. When so excluded, a weasel will do no harm about the premises, but may be depended upon to drive out or kill all the rats and mice.

MINKS.

Minks are excellent ratters, but as enemies of poultry are worse than weasels. They destroy fish also. The great demand for mink fur causes close trapping of these animals, and in the future they are not likely to influence greatly the numbers of rodent pests.

DOMESTIC ANIMALS.

Among the enemies of rodents often employed as aids to rat destruction are the dog, cat, and ferret.

DOGS.

The value of dogs as ratters can not be appreciated by those who have had no experience with trained animals. The ordinary cur and the larger breeds of dogs seldom make useful ratters. Small Irish, Scotch, and fox terriers, when well trained, are superior to most other breeds as ratters, and under favorable circumstances may be depended on to keep premises free from rodents. Much, too, may be done by the farmer or householder to increase the effectiveness of his dogs by removing obstructions to their work. Corncribs and outbuildings, when of wood, should not have floors close to the ground, but should have ample room below to permit dogs to move about freely.

With a little preliminary training, most terriers learn to hunt rats independently, and they thus become doubly useful on farms and in warehouses.

CATS.

When the black rat was the dominant species in Europe and America, cats were the chief dependence of the householder against rats; but comparatively few cats will venture to capture a full-grown brown rat. Then, too, the ordinary house cat is too well fed and consequently too lazy to be an efficient ratter.

Occasionally, however, one meets with rat-killing cats whose work in destroying the brown rat has decided value. These cats are rarely of the fine breeds, but generally of the common “tabby” variety, kept in barns or warehouses, fed on milk, and left to forage for their own meat. Managed in this way, cats are far less objectionable on sanitary grounds than when kept in the house as pets. In the country, on the other hand, barn cats are far more likely than the house-kept ones to run at large and prey upon birds and young poultry. Aside from the rat itself, we have no more serious enemy of birds and game than half-wild cats, many of which have been abandoned in fields and woods by the thoughtless. All things considered, cats do not rank high as destroyers of the common brown rat.

FERRETS.

Tame ferrets, like weasels, are inveterate foes of rats, and can follow them into their retreats. Under favorable circumstances ferrets are useful aids to the rat catcher, but their value is often greatly overestimated. They require experienced handling and the additional services of a well-trained dog or two to do effective work. Dogs and ferrets must be thoroughly accustomed to each other. A noisy or excitable dog is useless in ferreting. The ferret should be used only to drive out the rats, which are then killed by the dogs. If an unmuzzled ferret is sent into rat retreats under floors, it is apt to lie up after killing a rat and sucking its blood. Sometimes the ferret will remain for hours in a rat burrow or escape by unguarded exits and be lost.

Such experiences often discourage the amateur ferreter. Besides, ferrets are subject to diseases and require the greatest of care as to their food. For these reasons the use of ferrets to destroy rats, except in the hands of the experienced, is generally expensive and disappointing.

OTHER ANIMALS.

MONGOOSE.

The various species of mongoose (_Herpestes_ and _Mongos_) are destroyers of rats, and their importation into this country has often been urged. Many years ago they were introduced into Jamaica and Hawaii to save the sugar plantations from ravages by rats. The mongoose has, however, proved very destructive to native birds and poultry in the islands, and its introduction is now generally regretted. Its importation into the United States is prohibited by law.

ALLIGATORS.

In the South the alligator is said to destroy many rats along levees and banks of streams, and its protection has been urged on this account.

SNAKES.

Our larger snakes are beneficial in destroying rats, mice, prairie squirrels, and pocket gophers. As most of the food of snakes is obtained remote from human abodes, only a small percentage consists of rats.

BOUNTIES ON PREDATORY ANIMALS.

Whatever may be said in favor of bounties on the larger beasts of prey, those on hawks, owls, and the smaller fur-bearing animals can not be justified. Payments of this sort should cease, and laws should be enacted to protect species which careful investigations have shown to be mainly beneficial.

A few States still pay bounties for the destruction of foxes, weasels, skunks, minks, and raccoons. All of these, except the southern weasels, have valuable fur, and hence should be protected as a source of wealth. In addition they do far more good by destroying rats, mice, and other field pests than harm to game and poultry.

The payment of bounties on hawks of any kind is open to the objection that officials hardly ever discriminate between the harmful and the useful kinds, even when the statutes do so. Since the beneficial kinds are the more easily captured, public money is often paid out to reward what really injures the community. The bounty on owls is still more reprehensible, since owls are a more decided check to rodent increase.

The natural enemies of the rat exercise a steady, cumulative effect in restricting the numbers of the pest. That the effect is not greater is largely our own fault, since instead of protecting the birds and mammals that prey on the rat, we destroy them, sometimes even offering bounties on their heads. In future our aim should be to increase their numbers and to protect them in every way possible.

RAT PROOFING AS AN ANTIPLAGUE MEASURE.

By RICHARD H. CREEL,

_Passed Assistant Surgeon, United States Public Health and Marine-Hospital Service_.

To appreciate the great importance and absolute necessity of rat proofing as an antiplague measure, it is only necessary to consider the results that have followed its use as compared with other measures that have been relied on in recent years in combating this disease. These were, briefly, disinfection, evacuation, or destruction of buildings in infected areas, preventive inoculations, and destruction of rats either by poison or by trapping.

Plague was formerly believed to be communicable by aerial transmission and through the agency of fomites. Sanitarians have, therefore, put great faith in disinfection procedures, but the results have never been satisfactory, and it is only necessary to consider the method of transmission of plague to perceive the fatuity of bactericidal measures. Measures intended for the destruction of fleas are also of relatively small value. It is well worth while to destroy all fleas possible, but if those infesting the rat population escape, the efforts will have had little effect in preventing the spread of plague. It is only those fleas that infest rats and their habitats that are of importance in relation to the transmission of disease, and it is only by rat proofing that their destruction in rat burrows and runs can be accomplished.

Rat-proofing of individual buildings is of no recent date, but new emphasis was laid on rat-proofing as a separate and distinct antiplague measure by Passed Assistant Surgeon Mark J. White in an article written in the fall of 1907.[AK]

Footnote AK:

Journal American Medical Association October 19, 1907.

Disinfecting procedures must be regarded as of minor importance in plague prevention, except in pneumonic cases where its use is imperative. It is not intended to depreciate the value of disinfection, but rather to estimate its exact value as an antipest measure. Time and money should not be wasted nor a feeling of false security engendered by using an ineffective measure when others, as rat proofing, of much greater value are at hand. As an example of this might be cited an outbreak of plague in one of the refugee camps during the recent epidemic of the disease in San Francisco. This camp covered several blocks and housed between two and three thousand people. The camp grounds throughout and the houses were disinfected and disinfected well. At the same time, every effort was made to poison and trap rats. Notwithstanding these precautions, cases continued to occur, but when the houses were elevated there followed an immediate cessation of plague cases in the camp.

Another case of infected premises proved equally refractory to disinfection. The place was a large two-story frame dwelling located in the center of the city and in a good neighborhood. The yard was planked, as was also a part of the basement, the latter being used as a storeroom. On November 1 there occurred in this dwelling a fatal case of human plague, and plague rats were found at the same time. The place was disinfected in the usual manner and thorough measures were taken to trap and poison rats with apparent subsidence of infection, but on January 22 a plague rat was trapped, followed by another on January 31, after which the occupant of the building vacated it in great alarm. All planking was then removed from the yard and basement and concrete substituted by the owner, the place thereby being rendered thoroughly rat proof, and no plague rats were subsequently taken from that dwelling or in its immediate neighborhood.

In 1902 the plague outbreak was almost wholly confined to the Chinese colony. Chinatown was made the battle ground, and among other measures rat proofing was enforced, with the result that after the fire it was by far the most sanitary district in the city of San Francisco from a structural point of view. The buildings when erected were made rat proof from cellar to garret. The Chinese had had their lesson, and to their credit it must be stated that they responded with a greater show of intelligence than did some of the residents in surrounding districts.

Adjacent to the Chinese colony is the Latin quarter. In the rebuilding of this section, no attention was paid to rat proofing; consequently many of the buildings consisted of small shacks set on the ground or abutting some insanitary stable, and were therefore ideal rat harbors. On account of these conditions the natural results followed. Chinatown, on the other hand, which had contributed in the previous epidemic almost the entire number of plague cases during the epidemic of 1907, did not furnish more than two or three of the plague cases reported; that is, less than 2 per cent of the total cases reported, while the Italian colony, including North Beach district, probably furnished over 50 per cent of the total.

The evacuation or burning of buildings can hardly be called a successful measure any more than a retreat can be styled a victory; moreover, there can be no question from an economic standpoint as to the value of rat proofing over abandonment except in a few isolated cases of dilapidated insanitary property.

Schemes and plans for demurization, total or partial, have been as numerous and varied as they have been unsuccessful. Traps and poisons have been the agencies of destruction, but until some highly communicable epizootic peculiar to rodents shall have been discovered, absolute eradication of the rat can be considered as nothing less than impossible.

A recognized authority on plague, Major Morehead, of the Indian Medical Service, states that “rat destruction is of doubtful value,” referring, of course, to trapping and poisoning when those measures are used solely without auxiliary measures. He agrees with Japanese authorities in their arguments that as rat populations decrease, the breeding rate among survivors increases, due, obviously, in part at least, to increased food supply and harboring facilities. Such a result is assured where rat proofing is not accomplished at the same time. This latter procedure, by destroying rat harborages and cutting off food supplies bring about conditions unfavorable to breeding.

The total eradication of rats in a locality is not absolutely necessary, however, to the eradication of plague. If the rat population is kept within fairly low limits, rat centers destroyed, and such rat population as does exist well scattered and not congested, it is ventured that rat plague will disappear from a locality. Plague among rats in San Francisco ceased to appear when the number of rodents was reduced some 50 per cent, but such reduction was accomplished only after six months of ceaseless endeavor, which included also the rat proofing of the bakeries, stables, and markets in the city.

It is a logical supposition that close contact is just as essential for the propagation of plague among rats as it is for the spread of certain communicable diseases among human beings, the increase of cases being in direct proportion to the density of population and closeness of contact.

RAT PROOFING OF PRIMARY IMPORTANCE.

Without the general enforcement of rat proofing antiplague measures are bound to be more or less temporary and decidedly unsatisfactory. This subject is of immense importance to the public, both from a sanitary and a commercial standpoint, but the latter aspect of the question is more apt to prove of interest to most communities.

The measures necessary to render buildings rat proof are the same, however, whether they be instituted for sanitary or for commercial reasons. Rat proofing will, therefore, be considered entirely from a sanitary standpoint; but it can be understood that granaries, bakeries, butcher shops, packing houses, dwellings, and other places, if rat proofed for sanitary reasons, are just as much protected from depredation of the rat as though the work had been performed for commercial reasons alone.

Rat proofing has a twofold objective. It serves as a protection to the inmates of a building, and excludes rodents from sources of food supplies and harboring places. While rat proofing should be enforced as a general measure in all plague-infected localities, it is imperatively demanded in premises whereon have occurred cases of human or rodent plague.

Plague-infected localities or places that contain food must be rendered impervious to rats in order to insure the success of other preventive measures. Rats can be trapped or poisoned only when other food supply is excluded. A rat will enter a trap for food or will eat poisoned preparations not because of their greater attractiveness, but because of their greater availability. It therefore follows that rat proofing of food supplies is a prerequisite to success in rat eradication. The food depots requiring attention in the order of importance are stables, meat markets, bakeries, restaurants, groceries, warehouses, and private dwellings.

It is logical to suppose that the most common mode of infection is by reason of plague rats dying in the walls, roofs, or floorings of human habitations. As soon as the rat’s body is cold the fleas abandon it for another rat, some domestic animal, or human being. The risk to human inmates in such infected houses, therefore, is evident.

That rat proofing is a valuable measure is shown by the reports of the British Plague Commission where are mentioned the results following the use of rat-proof “go-downs” and those not so constructed. Additional evidence is presented by the fact that appalling epidemics of plague have ravaged India and the China coast, whereas in the Philippine Islands but few people die of the disease. It would appear that the comparatively few cases in the Philippine Islands were due to the fact that most Philippine dwellings are rat proof by reason of being elevated from the ground and the fact that the walls are thin and offer no refuge whatever to rats.

RAT PROOFING IS EXPENSIVE.

The almost insuperable obstacle that will usually confront the sanitary authorities in such work will be either the financial inability of the unfortunate community or the sordid unwillingness to make any expenditure that does not promise personal gain.

When the influence of the mosquito in the transmission of yellow fever was proven, recourse was had to mosquito proofing of both the sick and the well as a preventive measure. Rat proofing in plague is just as rational and necessary, but the financial expenditure contemplated thereby has been of such proportion as to cause the majority of sanitary authorities in different parts of the world to dismiss the idea as impossible.

To properly rat proof a city undeniably requires enormous expenditures, but no antiplague campaign was ever waged without an immense outlay of both money and labor. If allowed to progress unchecked, however, plague, either through ravages of the population or through commercial interference, is ruinous. To fight plague, therefore, is the only alternative, and a costly campaign should be anticipated and prepared for in advance. To merely put out traps and poisons without the preliminary rat proofing required can be productive of little good and no permanency. Such a plan of campaign may be attractive because of its relative cheapness, but any city or country that relies wholly on such measures is practicing false economy and deferring the day of reckoning.

It becomes evident, therefore, that rat proofing is of the greatest value as an antiplague measure, and that practical results to be expected are much greater than with any other method.

As has already been stated, the individual premises on which plague either among rodents or human beings has occurred demand first and immediate attention. The work should be extended as rapidly as possible from the point of infection so as to include the entire block and neighboring blocks.

While the chief energies should be centered on plague-infected foci, similar work should be carried on simultaneously throughout the city.

METHODS OF RAT PROOFING.

If plague occurs in the grounds of dwellings the following course should be pursued: All planked-over areas, including sidewalks, that might possibly shelter a rat should be removed, leaving either bare ground or, at the option of the owner, gravel or concrete used, the gravel being preferable. Small sheds should be elevated, or their ground floors concreted. Wood sheds should probably be left without flooring, wood kindling or other contents being piled on elevated platforms provided for the purpose. Stables on the premises should be treated as indicated in a subsequent paragraph relating to these structures.

The garbage depository must be given most careful attention. It should be a metal receptacle, preferably a galvanized can, water-tight to prevent seepage which would attract rats, and there should be a closely fitting lid. A can 2 feet in height without cover will not be proof against the incursion of rats.

The rat proofing of chicken yards is a difficult task as most chickens in private families are fed on table scraps, thereby attracting and supporting a fair quota of rats. The entire inclosure should be protected by wire fencing 6 feet high and of a mesh not larger than a half inch. Ordinary poultry netting is inadequate, the mesh being too large. The edge of the yard should be of concrete construction, the concrete extending 1 foot upward and 2 feet inward. If, on any subsequent inspection, rats have been found to have burrowed into the inclosure, the entire area should be concreted, sand or earth being allowed as a top dressing.

It would seem sufficient to confine these specifications to a feeding pen, but in practice this will not suffice, as a mere pretext of such a place would be built, and the housewife would continue to throw scraps into the unprotected yard.

The dwelling house itself should receive the most careful attention. If it is a small frame structure the cheapest and most effective means of rendering it free from rats is by elevating it, the minimum height being 1½ feet, measured from the most dependent joist. At the same time, all underpinning should be freed of rubbish or other material. It is not sufficient to raise the structure a few inches so as to permit the entrance of cats and other enemies of the rat. Such height and exposure must be secured as to deprive all rodents of cover.

If the house is of more substantial structure, and always if it has a cellar or basement, concrete or some other rat-proof material should be adopted. If sound foundation walls of stone or brick exist, then only the addition of a concrete floor is necessary. The stopping up of rat holes in any substance pervious to rats is at best a poor expedient.

The grounds must be rendered rat proof by piling all loose materials at such an elevation as will preclude rat harborage. All rubbish should be burned or otherwise destroyed. All basement windows should be properly protected against the ingress of rats, and if the _Mus rattus_ be present, even second and third story windows should not be considered too high to afford them entrance.

All loose materials on the premises should be properly piled, even though they are in a rat-proof cellar. It is not probable that the _Mus decumanus_ would remain or breed in any place where it could not burrow; but no encouragement should be offered to any rodent let in by carelessly left open doors. There have been cases where the black rat has lived, increased, and overrun a house which was structurally rat proof, but in which there was allowed easy access through open windows and doors, and great piles of loose materials and dunnage furnish harborage.

Stables are of twofold importance because they provide a source of food supply for rats and furnish harborage. All grain must be kept in a metal lined box or granary. A small stable is sufficiently rat proof if it has an elevation of 2 feet with clear underpinning, provided the floor is rendered impervious to falling grain. Barns of larger extent are best made rat proof by concrete flooring tight on the ground, and the area walls should be of concrete 1 foot high or of galvanized iron of standard thickness. The ingredients of concrete should be specified as to quality and quantity.