DISEASES OF STOCK

New Zealand Herald, Volume LXXI, Issue 21983, 14 December 1934, Page 6

DISEASES OF STOCK

INCIDENCE OF TUBERCULOSI

POSITION IN DOMINION

ENORMOUS LOSSES CAUSED

No. I

The incidence of tuberculosis in the herds of the Dominion, and the signs of its presence, are dealt with in the latest bulletin by Massey Agricultural College. New Zealand is fortunate, it is said, in having so low a percentage of the cattle population seriously affected with tuberculosis, although it is considered unfortunate that the disease is allowed to exist at all since it can be so efficiently controlled, if not completely eradicated. "One cannot lose sight of the enormous losses which the presence of tuberculosis in our herd produces both, directly and indirectly," the bulletin says. "Naturally enough, it is the direct loss which engages the farmer's mind. He mourns the loss of a good producer or it may bo a good breeder. That is a very obvious loss. But, what about the losses which aro going on unseen or not realised—loss of constitution and the trail of diseases which follow in its wake; breeding troubles, digestive troubles, lung troubles and uddor troubles?" Cause o 1 Disease

It is pointed out that tuberculosis is not one of those obscure conditions, like indigestion, which may arise from a great variety of causes. It has a definite cause—the bacillus of tuberculosis. It is produced by the entrance into the body of the animal, either by being taken into the mouth or bowel with food, or taken into the lungs by means of dust or into the skin through small injuries, of this organism.

When outside the body, the bacillus does not increase in numbers like some bacteria. Inside the body, it multiplies, forming in time definite areas of infection which are apparent to the naked eye. They may become so large that they may be seen as swellings on the surface of the animal body; and in the dairy cow it may show itself as a hardening of the udder. This does not mean that all hard udders are tubercular; many are, although they follow an attack of mammitis.

Once the organism is established in the animal body the organism can be found in the discharges of all cavities and .canals where the organism exists, e.g., in the dung from infested bowels, in phlegm from an infected lung, in the saliva, in the urine of an affected kidney and the vaginal discharges of an affected uterus. They are in the milk of a cow showing symptoms in the udder. They may be in the milk of a cow with an apparently healthy udder. They are not usually present in the milk of a cow whoso only symptom is a reaction to the test for tuberculosis. Animals Naturally Infected

All animals and birds may become naturally infected, the bulletin proceeds. Cattle and man are most frequently infected and then follows the pig, cat, dog, horse, camel and goat. Contrary to popular belief, natural infection occurs only after prolonged exposure and repeated actual infection. It is the degree of infection which determines the severity of the attack. This is a very important point to be used as an aid in eradicating the disease.

"Lesions" is the name given to those parts of the body which are damaged by the invasion of tho bacteria. Although the bacteria may be carried to all parts of the body in the blood stream, they are mostly found in the lymph glauds in a form most readily seen by tho naked eye. The glands which are most frequently noted by the farmer are those in the region of the throat, the glands situated just above the point of the shoulder, those lying immediately above the flank and those placed deep in at the attachment of the udder. , _ A . , , . Animals which show affected glands are called clinical cases to distinguish them from those which have tuberculosis, but do not show any signs whatever. It does not follow that because no lymph gland shows obvious symptoms of tuberculosis in an animal which failed to pass the test that the test must be at fault, lhe test applied to establish the presence of tuberculosis merely indicates its presence or not; it gives no indication whatever as to the extent or degree of infection. In cattle, where the infection lies mainly in the lungs, the animal usually emits a short, dry vigorous cough. This is not frequent at first, but only occurs through some unusual influence on the air passages, such as cold or dusty air. Thfi.v will filso coufxli if thoy are suddenly roused or take a drink of cold water. Nothing untoward will be noticed, for appetite will be good and also tho general appearance. If given a long drive tho tuberculous animal will be tho first to fatigue, although otherwise appearing healthy. Progressive Symptoms This short cough will probably last for months, in fact, it usually is present for some considerable time before any notice is taken of it. Gradually, however, other symptoms make their appearance and indicate more clearly that all is not well with the animal's lungs. The cough becomes more frequent and it may even become painful ; it is coarse at first and it may become feeble and almost noiseless. With the increase of coughing there is an increased number of respirations and further they are not so freely made as in the healthy animah This change in" the respiration and in its modo of action, is best seen after a little exercise. To try and diagnose the presence of tuberculosis by applying the ear to the thorax is absolutely useless. Most extensive growths can be present and not the slightest indifca.tion be given that they are there.