Equine infectious anaemia

“ Every fact in connection with its eruption and progress agrees perfectly with the hypothesis of transmission by contagion alone, and taken altogether the history excludes all other causes from being anything more than accessory. Before the days of modern bacteriology we had ample proof that glanders, rabies, sheeppox, lung plague, and Rinderpest were due to contagion alone as an 119essential cause, and so now we have the same evidence concerning equine influenza. ”

“ Causes.—The direct cause of horsepox is infection. A large number of predisposing causes favor the development of the disease, as in the case of strangles, and this trouble, like almost all contagious diseases, renders the animal which has had one attack immune. The chief predisposing cause is youthfulness. Old horses which have not been affected are less liable to become infected when exposed than younger ones. The exposure incident to shipment, through public stables, cars, etc., acts as a predisposing cause, as in the other infectious diseases. ”

“ Passing over a number of epidemics, we come to the next recorded equine influenza in A.D. 1299. In this year a catarrhal epidemic spread widely in Europe, (Parkes.) The equine disease is thus described by Laurentius Rusius, as it prevailed at Seville: “The horse carried his head drooping, would eat nothing, ran from the eyes, and there was hurried beating of the flanks. The malady was epidemic, and in that year one thousand horses died.” ”

“ When horse owners, legislatures and veterinarians can be educated up to the needs of the case our yearly local losses from equine influenza, and the occasional all 140pervading epizoötics of this disease can probably be abolished by the extinction of the germ on the Continent. ”

“ Bacteriology. Our knowledge of the bacteria of equine influenza is as yet very imperfect and uncertain. Galtier and Violet found streptococci and diplococci in the blood and tissues of cases showing intestinal lesions, and held that they were derived from musty fodder. Injections of infusions of such fodder into the trachea of the horse produced broncho-pneumonia, double pleuro-pneumonia, and at times intestinal or meningeal congestion. But there is no proof that the malady so caused, passed with the certainty and rapidity of equine influenza from horse to horse in the same stable. ”

“ Naturally acquired active immunity is induced by previous infection with E. rhusiopathiae. It is well known that immunity to acute SE follows clinical disease. Less well recognized is the immunity that can be induced by organisms of low virulence, which are capable of causing mild unnoticed subacute disease or subclinical infection.
PREDISPOSING FACTORS. SE can occur with other swine diseases, but the significance of preexisting infectious disease as a predisposing factor is uncertain. ”

“ 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. ”

“ The most important thing is to keep disease away from a herd or farm. To do this all sick or suspicious animals should be avoided. A grave form of disease may be introduced by apparently mild or trivial cases brought in from without. It is generally conceded that continual change and movement of animals are the most potent means by which infectious diseases are disseminated.
With some cattle diseases, such as anthrax, rinderpest, and pleuropneumonia, preventive inoculation is resorted to in some countries. ”

“ Even the transfusion of the blood of the sick, proved as harmless as the inoculation of the serous exudate. A probable explanation is found in the extreme diffusibility of the germ of equine influenza, which spreads over a city or county in a few days, attacking practically all equine animals. Inoculation is necessarily made at the time of the prevalence of influenza and at such a time all horses in a wide area are likely to be suffering from the affection. Those that are unaffected and therefore apparently available for experiment, are the immune animals. ”

“ This, like the foul, crowded stable, furnishes many more opportunities for infection and reinfection, so that the invasion of the exposed animal system is all but certain. Infection clings to the loading banks, yards, feeding stables, mangers, troughs, buckets, cars, litter, and manure, so that young horses shipped from the west to the Atlantic Coast States, very frequently come down with contagious pneumonia, and contaminate the stables in which they are placed. ”

“ Men vary almost as do the lower animals as regards infection. The quantity of tetanus toxin that will kill 400 horses will not bother a hen; Algerian sheep and the white rat are not affected by anthrax, but other sheep and the brown rat are very susceptible; a hog will not take glanders, man and a horse will; men, cattle, and monkeys have tuberculosis, dogs and goats do not; white men with few exceptions are susceptible to yellow fever and malaria, negroes are practically immune; negroes readily succumb to the fatal sleeping sickness, white men are almost immune ”

“ The active quality of the virus from the horses' heels is greatly increased after it has acted on the nipples of the cow, as it rarely happens that the horse affects his dresser with sores, and as rarely that a milkmaid escapes the infection when she milks infected cows. It is most active at the commencement of the disease, even before it has acquired a pus-like appearance ”

“ It is generally held that the flesh of the horse alone demands inspection, but with the known susceptibility of sheep, goats, and rabbits it can easily be conceived how the infection may reach man through his food, though horse-flesh is never consumed. That glanders has never been recognized as arising from the consumption of diseased sheep or rabbits does not prove that it has never reached man by this channel, any more than the absence of all recognition of the infection of man from the horse would prove the non-occurrence of such infection until the beginning of the present century. ”

“ Cases of chronic farcy and glanders, if not destroyed, may live in a depraved condition until the animal dies from general emaciation and anemia, but in the majority of cases, from some sudden exposure to cold, it develops an acute pneumonia or other simple inflammatory trouble which starts the latent disease and the animal has acute glanders. ”

“ Glanders, for instance, so virulent with the horse, the ass, and man, produce in the case of the dog only a local accident; peripneumonia, so contagious among horned cattle, is more benign in its action on Dutch than other breeds of stock; the cattle plague that decimates so many farms is communicated by cattle to each other from the slightest contact, while the closest and most constant association is necessary to communicate the disease to sheep, and even when they are affected its action is not severe. ”

“ Glanders, however, is always due to contagion, and in natural infection it may be contracted by inhalation of the bacilli, by ingestion of the virus with food or water, or by inoculation of a wound of the skin or a mucous membrane. Carnivorous animals—lions, tigers, dogs and cats—have become infected through eating the flesh of glandered horses; and men attending diseased horses are liable to be infected, especially if they have sores on the exposed parts of their bodies. ”

“ Convalescent horses may carry the germ for weeks, on the mucosa or in sequestra in the lungs, and contaminate horses with which they come in contact.
It is remarkable that the contagious pneumonia is far less diffusible on the air than influenza, so that it is much more constantly the result of direct contact of a sound, with an infected animal, or with a place or thing that the sick animal has contaminated. It therefore spreads much less rapidly, remains confined to individual stables for a length of time, and in the absence of active interchange of horses tends to die out of its own accord. ”

“ In the older countries horsemen too often accept strangles as inevitable. They expect that all horses will have it sooner or later, and it is not worth while to guard against it. The too absolute doctrine of the identity of the germ with the microbe of erysipelas, puerperal fever, contagious pneumonia, influenza, of the suppurations of the limbs and feet in sheep and cattle, and other streptococcic infections seems to corroborate this view. ”

“ These indurated nodules retain the virus and their power to give out contagion for almost an indefinite time, and predispose to the causes which we have studied as the common factors in developing a chronic case into an acute case; that is, an inflammatory process wakens their vitality and produces a reinfection of the entire animal. The blood of an animal suffering from chronic glanders and farcy is not virulent and is unaltered, but during the attack of acute glanders, while the animal has fever, the blood becomes virulent and remains so for a few days. ”

“ In our Eastern States and on the Plains, where the progeny of imported draught horses lose their digital hair, the malady is comparatively rare. A similar immunity has long been noticed in the horses of Spain and Africa. Disturbances of the digestion in heavily fed horses, subjected to transient confinement in the stall, and diseases of the liver and kidneys, must be recognized as further predisposing causes. The age of five and six when many horses change hands, and are subjected to extreme changes of stabling, feed and work, has furnished the greatest number of cases. ”

“ 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. ”

“ In acute glanders the contagion is found in its most virulent form, as is shown by the inevitable infection of susceptible animals inoculated with the disease, while the discharge from chronic semilatent glanders and farcy may at times be inoculated with a negative result; again, in acute glanders, as we have a free discharge, a much greater quantity of virus-containing matter is scattered in the neighborhood of an infected horse to serve as a contagion to others than is found in the small amount of discharge of the chronic cases. ”

“ For example, if a horse which has been so slightly affected with the virus of glanders that no symptoms are visible is exposed to cold, rain, or sleet, or by the rubbing of the harness on the body and the irritation of mud on the legs, the disease is liable to develop on the exterior in the form of farcy, while a full-blooded horse which is employed at speed and has its lungs and respiratory tract gorged with blood from the extreme use of these organs will develop glanders as the local manifestation of the disease in the respiratory tract. ”

“ Yet bovine animals are by far the most susceptible, by them it is mainly propagated, and upon them comes the greatest mortality. Infection, however, extends to all other ruminants,—sheep, goats, deer, elk, antelopes, gazelles, aurochs, yaks, camels, dromedaries, buffaloes, etc. Swine which show a pouch on the left sac of the stomach show a certain susceptibility, it killed the peccaries in the Jardin des Plants, Paris, and Viseur in France and Pluning in Sumatra, claim to have seen cases in the domestic pig. The horse, dog, rabbit, bird, and man are immune. ”

“ Anthrax or charbon may be defined as an infectious disease which is caused by specific bacteria, known as anthrax bacilli, and which is more or less restricted by conditions of soil and moisture to definite geographical localities. While it is chiefly limited to cattle and sheep, it may be transmitted to goats, horses, cats, and certain kinds of game. Smaller animals, such as mice, rabbits, and guinea pigs, speedily succumb to inoculation. Dogs and hogs are slightly susceptible, while fowls are practically immune. ”

“ Once in the stable, the disorder prevails through the stud, unless timely precautions are taken to prevent them being infected—removal from the stable is the most usual mode adopted—so easy is the infection conveyed from one animal to the other, that if the groom of the sick horse enters the stable of the healthy they rarely escape contagion. ”

“ As in the case of all other infectious diseases, the healthy should be separated from the sick horses and thorough disinfection of the infected stables, stalls, litter, and stable utensils should be carried out in order to prevent the recurrence of the disease. As a disinfectant the compound solution of cresol, carbolic acid, or chlorid of lime may be used, by mixing 6 ounces of any one of these chemicals with 1 gallon of water. ”

“ It is only in severe and advanced cases in which anæmia, emaciation and pallid innutritious muscles are marked features, that the flesh is objectionable, and then only as being somewhat lacking in nutriment and digestibility,—not because of poisonous qualities. Danger of infection to cattle might be apprehended, but, if used outside the infected area, the second condition of the disease—the boöphilus—is lacking, while within the existing area of prevalence of the fever, the propagation from the carcass to the animal is infinitely less likely than from one live animal to its fellow. ”