Pleuro-pneumonia. The disease of this name in the human subject is mentioned at PLEURISY; the following article deals with the disease in cattle so called. Pleuro-pneumonia Contagiosa is a contagious febrile disease peculiar to horned cattle, supposed to have originated in central Europe and thence to have been conveyed to all parts of the world. It cannot be certainly traced further back than 1769, when it was known in eastern France as Murie. Not till 1802 was it seen in Germany, 1824 in Russia, 1841 in Great Britain and Ireland, 1843 in the United States, 1858 in Australia, and 1864 in New Zealand. It is due to a contagium which gains access to the system by the lungs, and which, after an incubative period of from two or three weeks to as many months, induces extensive inflammatory exudations in the substance of the lungs and surfaces of the pleura, finally resulting in consolidation of some portions of the lungs, occlusion of the air-tubes, plugging of the blood-vessels, and, generally, adhesion of the pleural surfaces.
It is now clearly demonstrated that pleuro-pneumonia never occurs independently of infection, that it is not fostered by overcrowding, exposure, wet, damp, dirty hovels: these influences may predispose an animal to succumb more readily, or, in other words, to become a more suitable soil for the increase of the specific organism to which undoubtedly the disease is due, as stated by the writer in 1886. He stated that the organism was a micrococcus. It has since been discovered that there are three kinds of micrococci—viz. 1st, pneumococcus gutta-cerci, whose colonies, when grown in artificial media, resemble drops of wax; 2d, pneumococcus lichenoides, which grows in a thin white layer; and 3d, pneumococcus flavus, whose colonies are elongated or round in shape, and assume a beautiful orange tint. In addition to these cocci a bacillus is found, called by Arloing the pneumobacillus liquefaciens, and supposed by that observer to be the pathogenic organism causing the disease.
There is much variety in the manifestation of the disease. In some instances, especially during its first outbreak in a district, it runs a rapid course, destroying life in the course of a few days; in other cases, and these are the most numerous, its onset, course, and termination occupy a period of from two to eight weeks, or even longer; some animals recovering after the shorter periods, whilst others become emaciated, finally succumbing to an exhaustive diarrhoea, imperfect aeration of the blood, hydrothorax or water in the chest, the depressing influence of degenerated animal materials absorbed into the blood, and anaemia. The more prominent symptoms are slight rigors or shiverings, elevation of temperature, loss of appetite, secretion of milk diminished, an occasional cough is heard which is dry and hard in character, rumination becomes irregular, the bowels rather constipated, and the urine is scanty and high-coloured. In cases that do not begin to recover at this stage the signs of general disturbance more or less rapidly increase: the cough becomes more persistent, the respiratory movements increase in frequency, when the animal stands the elbows are turned out, and whilst recumbent the weight of the body is thrown upon the sternum or breast-bone—a posture in which, owing to the anatomical conformation of this bone, the animal can most readily expand the chest. The breathing is often but not always accompanied by a moan or grunt resembling the bleating of a goat.
Experience has led the great majority of professional men to the conclusion that the disease is not influenced by medicinal remedies; it runs a course. If the dose of the contagium is small, or the animal able to withstand a larger one, it terminates spontaneously in apparent recovery; but an animal which has thus apparently recovered still contains the germs and products of the disease, and remains a source of danger to others for an indefinite period, probably during the remainder of its existence. If, on the other hand, the dose of the specific cause be strong or the animal weak, death soon occurs. By the provisions of the Pleuro-pneumonia Act, 1889, all cattle suffering from the disease as well as those in contact with them have to be slaughtered, part of the loss being borne by the local authority.
Inoculation.—Experienced and successful inoculators are all agreed that inoculation with carefully selected lymph—and the non-success of the operation has been proved to be due to a careless selection of the inoculating fluid, and ignorance on the part of the operator—exerts a preservative influence and invests the economy of animals subject to its influence with an immunity which protects them from the contagion during a period not yet determined. Lymph for inoculation should be removed as soon as possible after the slaughter of an animal not too severely affected with pleuro. It should be a very light straw colour, the paler the better, and free from all blood and frothy mucus. It is removed from the borders of the diseased portion, collected with a porcelain spoon rendered aseptic, and conveyed into vials containing pieces of worsted thread a few inches long, which, as well as the bottles, have been aseptic. One of these worsted threads is inserted, by means of a needle made for the purpose, under the skin of the tip of the tail of each animal. Inoculation is practised to an enormous extent in Australia, many stock-owners there now believing that but for this it would be impossible to rear cattle successfully.