Zoonosis

“ 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. ”

“ 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. ”

“ A contagious disease is one that may be transmitted by personal contact, as, for example, influenza, glanders and hog-cholera. As these diseases may be produced by indirect contact with the diseased animal as well as by direct, they are also infectious. There are a few germ diseases that are not spread by the healthy animals coming in direct contact with the diseased animal, as, for example, black leg and southern cattle fever. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ Nor are the disease-bearing possibilities of the house fly limited to intestinal germ diseases. There is strong circumstantial evidence that tuberculosis, anthrax, yaws, ophthalmia, smallpox, tropical sore, and parasitic worms may be and are so carried. Actual laboratory proof exists in the cases of a number of these diseases, and where lacking is replaced by circumstantial evidence amounting almost to certainty. ”

“ When inoculated, all warm blooded animals contract the disease. Thus the carnivora and omnivora (dog, wolf, fox, hyena, jackal, cat, lion, badger and skunk and, to a less extent, the pig and horse) may become active propagators of the infection, which may spread widely among their herbivorous victims (cattle, sheep, goats, deer, rats, mice, chickens and pigeons) through their bites. Man suffers mainly through the attacks of dogs, cats and, in certain localities, wolves or skunks, but he is also liable to become infected from handling rabid domestic herbivora. ”

“ If we can now reproduce the original disease in other animals by infection with these isolated bacteria, the chain of evidence is complete beyond cavil and doubt. But this last step may not be the least difficult, as many diseases of mankind can not be transferred to animals, or only to some few species.
If we apply these rigid requirements, there are not many diseases of man whose bacterial origin is beyond doubt. As the most unequivocal instance, we can mention splenic fever, or anthrax, a disease of domestic animals, which sometimes attacks man, and is then known as malignant pustule. ”

“ It is possible that yaws, a non-sexually transmitted disease caused by a bacterium related to the one that causes syphilis, is also an heirloom disease; it infects our closest relatives, chimpanzees and gorillas [69] , [70] , and genetic analyses indicate that it has an ancient origin in humans [71] , [72] .
In contrast to heirloom species, “souvenir” species are those that are “picked up” along the way, as hominids carry out their daily activities. Souvenir species are usually zoonotic pathogens whose primary hosts are non-human animals; they infect humans only incidentally. ”

“ 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 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. ”

“ 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. ”

“ They are infectious when transmitted, not alone by contact but through the atmosphere. They are epizootic because they tend to attack animals generally or a given genus or family of animals generally when these are exposed to the infection. They are enzootic when confined to the animals in a given locality, the soil or conditions of which are favorable to the preservation of the germ in pathogenic potency, or to the production of a special susceptibility in the animal system. ”

“ In peptonised and glucosed gelatine the colonies are characterized as globules of liquefaction usually combined with gas. The germ is widely distributed in soils in general and not confined to limited areas like the bacilli of anthrax and black quarter.
Animals susceptible. The bacillus attacks man, horse, ass, goat, sheep, pig, mouse, Guinea pig, rabbit, white rat, cat, dog, chicken, pigeon, and duck. The mature ox is immune, but calves suffer. Dogs are often immune having already suffered from the disease. A first attack gives immunity from a second. ”

“ In the same way, one perceives how fallen fruits, all sorts of edible plants, as well as pond, canal, and even river water procured from the neighbourhood of human habitations, are liable to harbour embryos capable of gaining entrance to the human body. One individual suffering from tapeworm may infect a whole neighbourhood by rendering the swine measly, these animals, in their turn, spreading the disease far and wide. As already remarked, measles sometimes occur in great numbers in different parts of the body. ”

“ GLANDERS. —A contagious disease peculiar to the horse, ass, and mule, and may be communicated to human beings, and also sometimes to carnivorous [168] animals in menageries, by means of infected horse flesh, and also by means of inoculation to field mice, guinea pigs, dogs, cats, goats, rabbits, and sheep. Pigs are not readily susceptible and cattle appear to be immune. Like all diseases of a contagious or infectious character, glanders is due to a specific organism, known as the bacillus malleus. ”

“ And though men and quadrupeds might receive a disease from the same source of marsh-putrefaction, they might not afterwards be able to infect each other, though they might infect other animals of the same genus; as the new contagious matter generated in their own bodies might not be precisely similar to that received; as happened in the jail-fever at Oxford, where those who took the contagion and died, did not infect others. ”

“ They are sporadic when each case occurs without any casual relation to another. They are called panzootic when they attack all animals without apparent preference. The term panzootic is also used to describe those recrudescences of a disease or cycles of exalted pathogenesis which are observed in contagious diseases, which frequently last for years and again give place to a period of benignancy. Such cycles, of malignancy and benignancy, may be due to modified environment acting either on the disease germ or the animal system, or on both simultaneously. ”

“ Direct contact between healthy and diseased animals and the transport of spores, by combs, brushes, etc., favour contagion. The disease may not only be conveyed from one animal to another of the same species, but from the ox to man, and, with somewhat greater difficulty, from the ox to the horse. Cases of transmission from the ox to the sheep, pig, and dog have also been recorded. ”

“ Cause.—Germ (Bacilli of Fowl Cholera) gaining entrance to the body through the bowels, lungs or wounds [81] of the skin. Death results from toxic material produced while the germs are multiplying.
Symptoms.—All poultry, cage or wild birds are subject to this disease. The first symptoms are loss of appetite; diarrhoea is present and the discharge is almost white in color and tinged with transparent mucus. The affected bird becomes separated from the flock, seems weak and stupid and appears to be asleep; feathers are rough, the wings droop and the head is drawn in toward the body ”

“ From the earliest times certain disorders of the human family have been attributed with more or less evidence to infection from animals.
The discoveries of recent years have shown that the specific cause or microorganisms that produce certain transmissible diseases will attack both man and one or more species of lower animals. The most common of these microorganisms are those of glanders, rabies and tuberculosis, although anthrax, cowpox and foot-and-mouth diseases are not infrequently transmitted directly from cattle to man. ”

“ 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 ”

“ The pig may become affected with anthrax, foot-and-mouth disease and tuberculosis, and it also has its own particular variola. But the contagious diseases which cause enormous destruction of pigs are swine fever and swine erysipelas in Great Britain, hog cholera and swine plague in the United States, and swine erysipelas and swine plague in France, Germany and other countries of the European continent. ”

“ Now as our epidemic and contagious diseases are probably produced by disagreeable sensation, and not simply by irritation; there appears a reason, why brute animals are less liable to epidemic or contagious diseases; and secondly, why none of our contagions, as the small-pox or measles, can be communicated to them, though one of theirs, viz. the hydrophobia, as well as many of their poisons, as those of snakes and of in insects, communicate their deleterious or painful effects to mankind. ”

“ 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. ”

“ We have since then learned that man shares many diseases with the lower animals, tuberculosis, plague, rabies, diphtheria and pleuro-pneumonia, to mention only a few. We have also learned that certain lower animals, insects for instance, are intermediary hosts in the life-cycle of many minute parasites which cause serious diseases in the human being, amongst which malaria, yellow fever and the sleeping sickness are the most familiar. ”