Animal disease

“ The receptivity of the animal exposed is of first importance. Young animals are the most susceptible. The small rodents, the mouse, Guinea pig and rabbit are susceptible in the order named, followed by the sheep and horse and these again by the camel and ox. Among the wild herbivora the goat, deer and stag have a high susceptibility. Man is less susceptible yet contracts the disease readily by inoculation, inhalation or ingestion. Swine and dogs are comparatively little susceptible, yet they often contract the disease by eating the carcasses or discharges of anthrax animals. ”

“ This mucus contains worms which can be detected, or their ova observed under a magnifying glass. [55] In the latter stages of the disease, they cough severely at night. These attacks have a sub-acute character and prove very exhausting. The parasite by becoming entwined in balls severely affects the animal’s breathing which is always remarkably labored in the latter stages of the disease. The animal refuses to eat, becomes emaciated, anemic, mucous membranes of the eyes, mouth and nose become very pale and the sheep die in convulsions from suffocation. ”

“ Species that are unable to live independently of a host and are permanent parasites are usually the most injurious to the animal. This is especially true of parasites that are capable of puncturing the skin or burrowing into it. Temporary parasites may cause fatal forms of disease. This is true of the larva? of the sheep bot-fly, which develop in the sinuses of the head, causing severe inflammation of these parts, nervous symptoms and death. The character of the symptoms of a parasitic disease depends on the habits of the parasite, and the tissue or organ, that it may attack. ”

“ Communicability of Disease by Food.—Except the diseases associated with tape-worm and trichinæ, the only animal diseases which there is or has been ground for regarding as transmissible to man, through ingested meat, are cattle-plague, swine-typhoid, epizoötic pleuro-pneumonia, foot-and-mouth disease, anthrax and anthracoid diseases, crysipelas, and tuberculosis. ”

“ There are two points to be noted in an animal about to be killed, namely, whether the animal is healthy, that is, free from disease,—and whether it is in proper condition, neither too young nor too old, is well-grown and well-nourished. Among the diseases to which animals are subject, some are objectionable because of the possibility of the direct transmission of their disease to those eating the flesh, while others are objectionable because the flesh is spoiled and so causes irritation in the stomach and intestines of those eating it. ”

“ The presence of the microbe is not enough to cause the disease in the horse in continuous work, nor in that which is kept in the stable all the time, nor even in the horse that has worked steadily and then stood idle for a day, until he again goes to work. One animal or a few only out of a stable, are attacked, and there is no such active extension from animal to animal in the vicinity that characterizes the plagues proper. ”

“ Rest of the animal is absolutely essential while the disease continues, and is itself an effectual remedy in mild cases.
Besides the diseases enumerated, there are occasional epidemics, such as black tongue, black foot, or foot root, &c., which carry off great numbers of animals. Remedies for these are frequently not discovered, and the epidemic is allowed to run its course unchecked. The only preventives are such care, food, and management as the experienced herdsman knows to be best suited to the maintenance of the health and thrift of his stock. ”

“ As a rule, the more crowded and filthy the stable, the more impurities there are in the air. If any of the animals are affected with an infectious disease, such as tuberculosis or glanders, the moisture and dust may act as carriers of the disease-producing germs. Infectious diseases spread rapidly in crowded, poorly ventilated stables. The two factors responsible for this rapid spread of disease are the lowered vitality of the animal, due to breathing the vitiated air, and the greater opportunity for infection, because of the comparatively large number of bacteria present in the air. ”

“ Its advent in Europe as a new disease in the second third of the 18th century, its steady spread, its continued prevalence, and extension, concur with the infection of kennels and districts by the introduction of a sick dog, in demonstrating its purely contagious nature, and this implies a living microbe transferred from animal to animal. If any doubt remained it must be dispelled by the inoculations which have been constantly successful when made on young puppies, or dogs that have not previously suffered, and on cats. A first attack confers immunity. ”

“ The experiment stations naturally enough look askance, on the proposal to institute expensive experiments on a disease which dies out when the soil is improved. Deadly as the disease is to the individual attacked (man or beast) , it is not propagated indefinitely from non-milking subjects, by simple contact or proximity after the manner of plagues. It usually comes to an end by the death or recovery of the subject that has contracted it by consuming meat, milk, butter or cheese, the product of an infected animal. ”

“ An early diagnosis of the disease is necessary, as this enables us to use curative treatment when it will do some good, and take the necessary steps toward preventing the spread of the disease to neighboring herds.
Intestinal and lung worms are common in young hogs. The presence of these worms does not always indicate that they are the cause of the sickness and death of the animal. Such parasites are injurious and may cause disease, but it is only in rare cases that they cause death. ”

“ Some of the worst of all among them, the germs of typhoid fever, are carried on the feet of the common house fly, and planted all over the things that we are going to eat. Rats and mice also carry diseases—in their fur, on their feet, or even in their blood. So, too, do certain stinging, biting, and sucking insects; and when they bite or sting or suck the blood of some larger creature, they plant the seed of some disease in his body, where it grows and flourishes until the animal sickens and perhaps dies. ”

“ Though the fact is so well known, it is certainly one of profound significance that many animal diseases can be communicated to man, since it shows similarity, if not identity, in the minute structure of the tissues, the nature of the blood, the nerves, and the brain. Such diseases as hydrophobia, variola, the glanders, cholera, herpes, etc., can be transmitted from animals to man or the reverse; while monkeys are liable to many of the same non-contagious diseases as we are. ”

“ Radical treatment for the disease is far from generally satisfactory. Too often the affected animal is still in the environment which has tended strongly to its development, and it is impossible to secure a satisfactory change. ”

“ But some human diseases do not attack animals, and in the case of diseases that may be given to animals it is frequently uncertain whether the disease produced in the animal by such inoculation is identical with the human disease in question, owing to the difference of symptoms in the different animals. ”

“ The direct experimental inoculation from horse to horse infallibly conveys the disease so that the flies are not needed to pass the parasite through an intermediate stage of its existence, but merely to carry it. It follows that no particular fly is the bearer but any insect may carry the infection from a bite or sore to inoculate it on a sore or by a bite on a fresh animal. ”

“ All the glands in the body have now become involved or poisoned, and death must follow in the course of ten or fifteen days, as the constitution of the animal may not be in a condition to combat the disease.
If this disease be annoyed by inoculation from the farcy heads of farcied animals into suppurating sores on other animals, it will be very slow in its progress, especially if it attack the other in a region remote from the lymphatic. If in a saddle-gall, it will make sores very difficult to heal. ”

“ Therefore, in the control of infectious diseases prevention is the most important procedure. The isolation or segregation of healthy animals from infected ones should be primarily considered, and if at any time an animal manifests the symptoms of an infectious disease it is essential to protect the others from such a source of danger. In some of the infectious diseases it may become advisable to kill the infected animals in order to avoid the spread of the disease. ”

“ An infectious disease may be defined as any malady caused by the introduction into the body of minute organisms of the vegetable or animal kingdom which have the power to multiply indefinitely and set free certain peculiar poisons which are chiefly responsible for morbid changes. Nearly all diseases of animals for which a definite cause may be attributed are caused by bacteria; such are tuberculosis, anthrax, blackleg, lockjaw, and others. ”

“ All virus, excepting such as may live in the soil, is killed sooner or later by drying and sunshine, and the importance of these factors in the daily life of animals need not be insisted on here. Finally, all sanitary measures which contribute to the healthfulness of animal surroundings are directly or indirectly inimical to disease germs, and all carelessness in the keeping of animals may be regarded as an ally of these destructive organisms. ”

“ In view of the diffusible nature of the germ, however, we must recognize that all secretions may be quickly contaminated as soon as they are exposed, and therefore no product of a sick or suspected sheep can be held to be safe, and all should be treated as presumably infected. The most dangerous products and those most liable to convey the disease are wool, hides, litter, buildings, yards, covers, parks, railway cars, boats, manure, urine and milk.
Living creatures like men, dogs, cats, birds, vermin, flies and other predacious insects are occasional bearers of infection. ”

“ On the high, dry lands, on the other hand, the natural tendency to immunity would be still further enhanced, as the most susceptible animals which contracted the disease, in even such a healthful district, could be in no sense fit for reproduction, and should therefore be doubly condemned. ”

“ Definition: infectious disease caused by bacillus, attended by productive inflammation, tubercles, necrotic degeneration, caseation, fibroid change, calcification or ulceration. Animals susceptible: python, salamander, carp, fish, birds, rodents, sheep, goats, solipeds, cattle, dogs, cats, apes, swine, wild ruminants, kangaroo, carnivora, cage birds, civilized (housed) man. Geographical distribution: with dense population, Central Europe, Britain, Eastern States ”

“ These diseases are caused by different microorganisms that may be found in the digestive tract and air-passages of healthy birds, insanitary conditions and decomposed feed, especially meat. It seems that under certain conditions, such as insanitary quarters and birds that are low in constitutional vigor and weakened from other causes, certain germs may become disease-producers. The death rate from mixed infections is very heavy in poultry.
The symptoms vary in the different cases. The disease may be highly acute, as in limber neck, or chronic, extending over a period of a week or more. ”

“ With the exception of the rare disease known as glanders, the horse is not believed to be directly responsible for any of the maladies from which the human being suffers, but it is well established that fully 95 per cent. of house-flies hatch in the manure of these animals, and they, therefore, become indirectly responsible for some of the most serious diseases affecting the human being. It is thus seen that almost every object with which man comes in intimate contact is capable of conveying to him the poison of one or more diseases. ”

“ Under other circumstances the germ, temporarily shorn of its power, lingers in city and dealers stables, biding its time until circumstances become more favorable for a new general outbreak.
Immunity largely explains the comparative mildness of the last cases in any particular locality. The more susceptible animals are attacked first and most severely, while the partially immune ones, which for a time resist, throw off the disease with greater readiness. ”

“ It is a common experience to see a malady transformed through the effects of heredity or acquired immunity, through environment or the temporary mitigation of virulence in the germ; and again we see the same disease, no longer restrained by such inhibitory conditions, bursting forth as a malignant and deadly plague. We have, therefore, no warrant for the hypothesis that a pathogenic germ which, under given conditions of life, has lost in pathogenesis, but not in vitality, should continue forever to exist as a harmless microbe. ”

“ Susceptibility to plague of the animals of the farmyard, and the chronicity and ill- defined nature of the disease which not infrequently occurs among these animals, as well as in rats, are likely to be important factors in continuing the disease in those endemic centres where people, cattle, pigs, and poultry, in addition to the ordinary domestic vermin, are housed under the same roof, and even in the same room. ”

“ II. Scientific Results.—We come now to consider the results of experiments on animals, but we must remember that not we alone, but animals also, owe a great debt to them. Great epizootic diseases like anthrax, swine-fever, chicken cholera, silkworm disease, pleuro-pneumonia, glanders, Texas cattle fever, blackleg, tuberculosis in cattle, have killed yearly millions of animals, and have been brought under better control by these experiments. The advantages that have been obtained for man may be arranged under two heads— (A) Physiology, (B) Pathology, Bacteriology and Therapeutics. ”