CONTAGIOUS PLEURO-PNEUMONIA OF CATTLE.

New Zealand Journal of Agriculture, Volume XXIX, Issue 6, 20 December 1924, Page 390

CONTAGIOUS PLEURO-PNEUMONIA OF CATTLE.

C. S. M. HOPKIRK,

B.V.Sc. (Melb.), Veterinary Laboratory, Wallaceville.

Pleuro-pneumonia is a disease of the lungs of cattle caused by a very minute organism, which, like the virus of foot-and-mouth disease, is a filter-passer. The disease was known and described as early as 1765, and since 1794 has been recognized as of a particularly contagious nature. Several commissions have made a study of the disease, which caused great loss on the Continent'during its spread from Switzerland to all neighbouring States. In 1839 it passed from Holland by means of imported cattle to Ireland, and a few years later to England and the lowlands of Scotland. The United States of America also became infected from the purchase of a ship's cow as early as 1843. Later still Australia and South Africa became affected. The United States and Great Britain were able finally to eradicate the disease by slaughter of herds showing affected animals, and the trouble is now confined to Russia, Spain, Africa, Asia, and Australia. New Zealand and Tasmania, thanks to early good fortune and later to rigid quarantine arrangements, have always been free from the disease. THE CAUSATIVE ORGANISM. The organism causing pleuro-pneumonia is just visible with , the aid of the highest power of the ultra microscope as a highly refractile spot, and. until recently the exact shape was not known. However, ’ by a special -power photographic apparatus where exposures were made in ultra violet rays, the organism has now been found to resemble a yeast in shape and method of propagation. It has recognizable staining affinities, and was first cultivated in 1897 on artificial media by Nocard and Roux, who placed some of the lung exudate into broth in a collodion capsule and introduced the capsule into the peritoneal cavity of a rabbit. In twenty' days the rabbit was killed and the broth found to be cloudy with a growth of the organism. Later this organism was cultivated in the incubator at blood-heat on solid media, and also in liquid media containing serum in a certain percentage (8 per cent.). After the liquid media had been sown, to ensure that no contaminating organisms would be found present, the whole was run through a porcelain filter. For culture purposes the organism is found pure in the lung or pleural exudate. Heat easily destroys the organism (58° C. for one hour), and cultures are found dead after one month. In ideal circumstances virulence may be retained for ten months. The lymph is attenuated considerably by air and light in three weeks, and heating at 55 0 C. greatly modifies the action of the organism when injected into an animal. -

TRANSMISSION OF THE DISEASE

It has been proved by experiment and careful watchfulness in the field that transmission is only by animal contact. One animal must breathe moisture and virus-laden atmosphere expired by an affected beast at a distance of, at most, only a few feet. Consequently the

disease spreads from field to field by contact of one animal with another over the boundary-fence. It is impossible to set up a typical form of the disease in any other way, and cattle which have died from pleuro-pneumonia are not a source of danger to healthy cattle on the same pasture. Contact cases take about twelve, to twenty days to contract the disease. When a young animal — must be at least six months old, as younger animals are immune to the diseaseis inoculated in the flank with a small dose of the virus-culture or lymph exudate from the lungs, after six to twenty-seven days a rise of temperature occurs and a doughy swelling appears at the seat of . inoculation. The neighbouring -glands become enlarged, and sometimes there is a breakdown of the centre of the swelling. If a bruising of some other part of the body has occurred there is occasionally a lesion formed in the bruised area, which rather, disproves the belief that the disease is purely local in character. The lungs have never been known to become affected from any form of inoculation. Ingestion of affected material is. also harmless. SYMPTOMS. At first the symptoms are often confused with digestive disorders, this being due to irregular rumination, capricious appetite, dull appearance, and roughened coat ; but in a few days the gait of the animal changes and becomes slow and uncertain, it cannot turn without evidence of pain, percussion of the thorax causes a cough and often a peculiar moan, the pulse is accelerated and the temperature high. At a later stage the fore limbs are kept wide apart, the animal remaining still;, the nose is lowered and projects in line with the neck; breathing becomes abdominal, and the cough is more frequent and usually moister. There is very often at this stage' a characteristic moan during expiration, sometimes marked and at other times hardly discernible, at the nostrils. By percussion methods a line of pleural effusion can be made out in the thorax, and a zone of dullness over a large area of one side of the lungs. Sometimes both sides are affected. This dullness is due to increased density of the lung, through effusion of exudate into the lung - tissue, so that pneumonia and pleurisy are combined, as indicated by the name of the disease. Often an oedema develops beneath the chest. Abortion is a common sequel. The animal may last for ten to fifteen days, when it. may die either from suffocation or of general poisoning from the disease. Should the cow live,, the lesions become chronic, and the animal either survives for several weeks or gets partially well to a stage when she is a menace' to all her neighbours in the herd as long as she lives. In an outbreak the symptoms as described are those usually seen, but sometimes the animal may die from a peracute form in about two days, or else, in a subacute form, linger on for weeks. In mild cases only a small rise of temperature will be present to give any indication that the animal is affected.

, In a clean country where the disease has recently been introduced the death-rate is about 80 or 90 per cent., but where the trouble is old standing and precautions are taken 30 per cent, is reckoned upon.

DIAGNOSIS. . A diagnosis is based usually on a knowledge of the prevalence of the disease, the number affected in a herd, and on post mortem examinations of a suspected case. Pleuro-pneumonia may be mistaken for several other conditions before death, but after death the state of the lungs narrows the trouble down to one of two —haemorrhagic septicaemia (“corn-stalk disease of U.S.A.) and pleuro-pneumonia. These are easily differentiated with the aid of the microscope, as they are caused by totally different organisms. - Seen before incision the lungs appear non-collapsed and swollen ; they sink in water, and feel more or less like liver; when incised a clear straw - coloured fluid exudes and later coagulates. This cut. surface has a beautiful marbled appearance, which is caused by the white streaks of connective tissue running between the lobules being greatly distended with exudate in the lymph spaces. Between these white lines are islands of various colours, some dark red, others scarlet, and others, again, muscle-coloured or pale yellow-pink. This thickened area of the lung fades off into the still active lung-tissue. ' As the disease becomes chronic the solid area is enclosed in' a capsule of fibrous tissue, and, if the animal survives, the piece of lung so enclosed becomes necrosed. and dry owing to a shutting-off' of the blood-supply. This condition is dangerous, as the area may open up at any time, and the organism of the disease appears to be ever ready to take advantage of such an opening. The position is that either the animal will get a second attack of the disease or it will act as a potential carrier for the rest of the herd. It is for this reason that any cow affected must be killed and not allowed to convalesce. Only rarely, does a sloughing of the lungs occur, as the lung-lesion is so well enclosed that other organisms do not easily gain entrance, and they are seldom imprisoned in the area. On the walls of the lungs there is usually to be seen a thick creamy layer of deposit, with some 2 gallons of a clear fluid in the chest-cavity itself. Where intramuscular inoculation of an animal is carried out for obtaining active lymph, the muscles show just such a marbling as is seen in the lungs, together with a quantity of serum which causes the doughy condition of the swelling. There are several scientific laboratory methods of identifying the disease : (i) Cultivation in broth plus serum, after passing through a porcelain filter; (2) the agglutination test, in which the serum of an affected animal in certain dilutions has the property of causing the organisms to mass together and form a deposit on the sides and bottom of the tube ; (3) the complement fixation test. The last two methods have been perfected recently by 'Major G. Heslop, at the Veterinary School, Melbourne. Major Heslop also keeps pure cultures in stock for the work of immunizing animals against the disease. ■ • IMMUNIZATION. ' To gain an immunity several methods are in vogue. That of Willem is the simplest. By this method a small amount of lung-lymph .is taken from an animal killed while affected with an acute attack of the disease, and inoculated into the tip of the tail. The method has several drawbacks, such as the. loss of tails in .5 to 15 per cent.

of cases, the transmission of other diseases, such as tuberculosis, into the inoculated animal, and sometimes death from general invasion of the perineal and pelvic regions. Immunity is established for twelve months. Pasteur, by his . method, obtained lymph from an experimental animal from the inoculated area behind the shoulder, and. mixed his lymph with one part of glycerine to two of lymph. This material remains, effective for six weeks if kept on ice. By this method'no other disease is likely to be given to the animals being immunized. Theiler, in South Africa, advocates drenching cows with either the lymph itself diluted with water or else pure culture. Many say that no immunity is established by this method. Heslop, in Australia, and many workers in France prefer to use a pure culture for tail inoculations.- By this method there is little loss of —only 0-7 per cent, in France-and the risk of inoculating other diseases is absent. Nocard prepared a hyper-immune serum, and by giving large doses could obtain a passive immunity for eight to ten days, and even a curative action with huge doses, but this is of little practical value in the field. CONTROL MEASURES. In order to combat the spread of the disease in any country stringent precautions are necessary. In Victoria the regulations make it necessary for the farmer to notify the Stock Department at once by wire of such an Outbreak, or even of a suspected case. The farm is at once strictly quarantined against outgoing animals, except where •affected cattle are being driven to the abattoir under orders from the Veterinarian in charge. The neighbours are placed under a zonary quarantine, which necessitates them having their cattle effectively inoculated. Stock visibly affected are slaughtered at once. Others have their temperatures taken daily, and a rise of one degree acts as a death-warrant, as no animal must be allowed to recover from the disease to be a potential carrier. Occasionally the agglutination test is applied in doubtful cases on a farm where the outbreak is not typical. Cattle not affected are inoculated with culture or with lymph from the lungs, and in the zonary quarantine, so long as a death does not occur, no temperatures are taken. Quarantine lasts for thirty to sixty days from the last known case. The very serious nature of pleuro - pneumonia will thus be seen. Were the disease to find its way into this country it might very quickly take control and spread from district to district, causing some 80 per cent, of deaths in the affected herds. The necessity for the existing restrictions on the importation of cattle into New Zealand will readily be apprehended by stockowners. -

Vaginitis in Dairy Cows.— In regard to the 1923-24 season the Live-stock Division reports that a considerable amount of trouble was again experienced among dairy herds from vaginitis in its various forms, often accompanied by sterility. Fortunately, although indications point otherwise, a number of the cows affected continue to hold and come into profit at the usual time, but others do not, and the loss is severe. The treatment advised by the departmental officers has been found to give satisfactory results, but, owing to failure in many cases to detect it in its early stages, the treatment has to be continued over a. much longer period, and it is sometimes difficult to get farmers to conscientiously carry it out over the period necessary.