Swine fever

“ So difficult is it at times to discover the source of the infection of swine fever that certain persons who are not amongst the strongest believers in the practical knowledge of the members of the veterinary profession assert that swine fever need not necessarily be the result of infection, but that injudicious feeding or the neglect of sanitary arrangements will sometimes cause an outbreak. ”

“ As a general rule swine fever assumes this non-acute and slowly progressive form in pigs which have arrived at an age when their powers of resistance to disease are materially increased, i.e., in animals of eight or more months old ”

“ The owner then merely carries out the instructions supplied to him by the police so that it is almost unnecessary to state that the symptoms of swine fever are several. At times the attack is of so virulent a nature that a pig may take its food all right in the afternoon and be dead the next morning, no discoloration of the skin or other external symptoms being visible before or immediately after death. ”

“ 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. ”

“ Swine fever, like typhoid fever in man, is essentially a disease of the digestive system, its chief characteristic being certain morbid changes of a well-marked nature which are found upon the surface of the mucous membrane in some part of the alimentary canal. ”

“ What are termed “swine-fever infected areas” are scheduled by the board when and where circumstances seem to require, and the movement of swine within such areas is prohibited, much inconvenience to trade resulting from restrictions of this kind. Frequently, moreover, the exhibition of pigs at agricultural shows has to be abandoned in consequence of these swine-fever regulations. ”

“ Nature did not construct him for such conditions, but for an open-air life, and it is not really surprising that he develops swine-fever, which, by the way, is remarkably like the fevers that afflict overcrowded, filthy, and unventilated human dwellings. Cowhouses are regulated, but pigsties are not. ”

“ In some of these the duration of incubation (in swine plague six to fourteen days and in Texas fever one month) serves to distinguish, while in the majority the microzyme is globular (Texas fever, micrococcus of fungi-poisoning, chicken cholera) ; in swine plague the cocci are arranged in pairs; in black quarter the microbe is a refrangent ovoid, single or in chains of two or three and a motile linear body with a refrangent nucleus in one end; and in milk sickness the germ is a spirillum. The germs are far more likely to be detected in the local lesions and lymphatic glands than in the blood. ”

“ An acute infectious disease of the lower animals but especially of ruminants, characterized by a slight fever and the eruption of vesicles, or ballæ on the skin and mucosæ, and usually those of the mouth, feet and teats.
Susceptible Animals. The animals that prove the most obnoxious to the disease are the bisulcates—large and small ruminants 317and swine. Man however is susceptible as are also horses, dogs, cats and fowls, when they are inoculated or fed upon the infected milk or other products. It is doubtful if any warm-blooded animal enjoys an immunity. ”

“ Susceptibility to diseases is as variable as sensitiveness to vegetable and animal poisons. Judging from the current opinion that putrefying animal matter is the principal bearer and transporter of infectious germs, we are forced to ascribe a high degree of immunity to certain animals which, like swine, ducks, chickens, and rats, are accustomed to select their food from places where such matter is accumulated. Predisposition for splenic fever is stronger among herbivora than among carnivora; birds of prey seem to be quite free from it. ”

“ Bacillus 1.5 μ, anærobic, easily destroyed in pens, in pork. Pathogenesis: swine, rabbits, mice, rats, pigeons and sparrows suffer. Rabbit germ less fatal to pigs. Immunization, advantages and drawbacks. Technique.
Definition. A microbian disease of swine manifested by high fever, great prostration and muscular weakness, a violet tint of the visible mucosæ, red or violet discoloration of the skin in spots and patches or universally, enlarged lymph glands, encreased size of the spleen, and general congestion of the capillary plexus. ”

“ The diseases to which swine are usually subject act quickly, as a rule, and are speedily fatal, as in the case of hog cholera, whereas the diseases most to be feared in cattle and sheep are those of slow activity and those of a nature which is often not revealed until slaughter, namely, tubercular diseases. In so far, therefore, as infection from disease is concerned, previous to slaughter, it appears that the flesh of swine is less objectionable and less open to suspicion than that of cattle or sheep. ”

“ Acute and rapidly fatal cases of swine plague furnish lesions indicative of a hæmorrhagic septicæmia. The abundance of petechiæ on the skin, mucosæ, serosæ, and tissues generally, with circumscribed hæmorrhages, congestions, inflammations and exudations, agree in the main with what is observed in the acute examples of hog cholera. If the congestive or inflammatory lesions, concentrate in the lungs rather than the bowels it assists in the diagnosis of swine plague. The swelling and blood engorgement of the lymph glands are nearly alike in the more acute types of the two diseases. ”

“ The health and vigor of the animal exposed is not without its influence in case of attempted invasion by a virus of diminished potency.
39Dry, warm beds with plenty of air and light are essential to vigorous health and the usual damp, filthy, dark pens are depressors of the vital forces and virtually invitations to hog cholera as to other diseases. The close packing of swine under manure or under rotten piles of straw where they often suffocate each other is to be carefully guarded against. ”

“ 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 bacillus of swine plague may be found on the air passages of swine and other animals that are not themselves, at the time, susceptible to the disease, and these animals accordingly become the occasions of what have been thought to be spontaneous outbreaks, and of invasions of fresh herds after the introduction of healthy pigs which have been thought to be beyond suspicion. ”

“ No animals that occupied the yards before disinfection should be allowed to mingle with the new stock, as they at times carry the microbe, though themselves apparently healthy and immune. All regulations as to railway and boat transit, recommended under hog cholera, are equally applicable to swine plague. The possibility of protecting private herds, by keeping them in special pens, holding two or three each, is also the same for swine plague. ”

“ 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. ”

“ Human beings get nearly all their diseases from other human beings who are sick; horses, from other horses; cattle, from other cattle; swine, from swine, etc. Occasionally transmission from one species to another occurs. Tuberculosis of swine most frequently results from feeding them milk of tuberculous cattle or from their eating the droppings of such cattle. Human beings occasionally contract anthrax from wool, hair and hides of animals dead of the disease or from postmortems on such animals; glanders from horses ”

“ 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. ”

“ Pseudo-membranous pharyngitis has long been recognised as a contagious disease of swine, attacking especially swine kept in herds or in close, insanitary pens. Young pigs are more liable to attack than older animals, perhaps, owing to the older animals having suffered the disease in early life. ”

“ Not long ago, the writer was impressed with the severity of this disease by having brought to his attention an epidemic in a herd of swine caused, presumably, by feeding waste which contained rinds of Western pork, infected with trichinæ and many examples may be found of regular epidemics caused by persons eating raw ham infected with this disease. Fortunately the means of prevention is very simple and implies merely the thorough cooking of the meat. If persons will avoid eating raw or underdone swine flesh in any of its varieties, no danger need be apprehended. ”

“ These are more liable in youth than in maturity, partly no doubt because the older animals have already suffered and attained to an immunity. Modern observation has shown that pharyngitis with formation of false membranes is especially common in swine plague, and the present tendency is to refer all such cases to that category. It is however altogether probable that the occurrence of local irritation with the addition of an irritant or septic microbe altogether distinct from those of swine plague or hog cholera, gives rise at times to this exudative angina. ”

“ Swine may produce up to 108 infectious doses contained in aerosols per day during peak viremia (Sellers et al. 1971) , which is up to 1500 times greater than that produced by cattle (Donaldson and Ferris 1980) . In hot, arid regions, the disease is mainly spread by direct contact, as aerosols cannot travel long distances due to low humidity and high temperatures. Other means of spread include contaminated semen, meat and milk products, and fomites. ”

“ The horse that has apparently recovered from dourine still conveys the disease to others with which it has sexual congress; the recovered syphilitic person is by no means eligible for marriage; the recovered pig continues to carry the infecting swine plague bacillus in its air passages. In short, it is the rule that the immunized animal can with safety to itself carry a germ that readily infects its nonimmunized fellows. ”

“ 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. ”

“ Because of the hog’s habits, it is difficult to see any practical measures which can be adopted to prevent infection. Feeding from troughs and supplying plenty of pure drinking water will decrease but not exclude the disease. Leuckart’s advice to the Germans, “Swine should be kept in a less swine-like manner,” holds good in all countries and in connection with all diseases. It is equally impossible to suggest practical methods of treatment. ”

“ Symptoms.—After a period of exposure to infected soil, which may vary from 13 to 90 days, and which will be more fully discussed under the subject of cattle ticks as bearers of the Texas-fever parasite, the disease first shows itself in dullness, loss of appetite, and a tendency to leave the herd and stand or lie down alone. A few days before these symptoms appear the presence of a high fever may be detected by the clinical thermometer. The temperature rises from a normal of 101° to 103° F. to 106° and 107° F. There seems to be little or no change in temperature until recovery or death ensues. ”

“ ECZEMA IN SWINE. Secondary skin lesions, maculæ, vesicles, seborrhœa, crusts. Impetigo of young: cold weather: exposure: filth: spoiled or improper food. Symptoms: eyelids, etc., show itchy, red, swelling, pustules, scabs, erosions, may affect nose or mouth. Duration 20 days. Hot weather aggravates. Treatment: cleanse: soapy washes: emollient ointments, astringent lotions, saline laxative, diuretics.
Disease of the skin is by no means uncommon in swine, but it occurs mostly as a manifestation of an acute general malady. ”

“ Among conditions contributing to a spread of infection, nothing is more potent than a free movement of ruminants, and swine whether determined by war, trade, or the intermingling of different herds on commons or unfenced ranges. In infected countries, in which cattle are distributed through large central markets there is always a wide extension after one of these fairs, the infection being narrowly circumscribed to herds receiving cattle from the fair, or those that have travelled on the same roads or fields after the market cattle. ”