Text book of veterinary medicine, Volume 4 (of 5)

by James Law

Another distinction of the European abortions, is in the presence of the microbe in European form in the digestive organs of the calf, and that the viable calves of infected cows are liable to die of intestinal disorders a few days after birth. Galtier, the Marquis de Poncius and Pry insist strongly on this. On a farm on the estate of the Marquis, where abortion had prevailed for twenty years, the calves of infected cows show at birth, or very shortly after, symptoms of broncho-pneumonia and of a complication of nervous disorders. They are breathless, wheeze, discharge from the nose, cough, scour, have convulsions or other nervous trouble. A large proportion of such calves die; and their lungs are found in part red, consolidated and devoid of air and the bronchia contain a muco-purulent product. Lesions denoting inflammation of the serosæ of the lungs, liver and intestines are common. This coincidence of a fatal disease in many of the surviving calves is exceptional among the aborting herds of New York.

In noting the evidence of a wide difference between the prevalent American and European forms of abortion in cows, one should be prepared to go farther, and accept if need be, still other distinctive forms in each of the two continents. Any catarrhal condition of the uterine mucous membrane, is a recognized hindrance to conception, and cause of abortion, and we must recognize that the forms of invasion of the womb by pus microbes are as numerous as there are irritant germs capable of living in the membrane. The question as to how many of these can produce contagious abortion is to be determined by the susceptibility of the membrane to irritation by each germ, and whether the latter can retain all its power of survival and virulence in passing from one animal to another. The presumption is, therefore, in favor of a variety of forms of contagious abortion, each due to its own specific microbe or microbes, rather than of a single unvarying type of the disease. In some the affection appears to be a purely local one (American), the microbe being confined to the genital or genito-urinary mucosa, whereas in others the microbes (Bangs’, Galtier’s, etc.) live also in the blood producing a general infection.

Two great types at least have been demonstrated in Europe and America. Whether future investigation shall show the presence in one of these continents of the types as yet only known in the other, remains to be seen. If the particular forms should turn out to be limited to different continents we are at once confronted with the necessity of an international sanitary quarantine, and inspection. Matters are bad enough now in our dairying districts, but if we are to be open to the importation of new types of abortion, which do not mutually immunize against each other, but which may be taken one after another in succession through a series of years, they may easily become incomparably worse.

Acquired Immunity. The question of persistent abortion year after year, in the same animal, is most important. If a first contagious abortion entails a second, a third, a fourth and a fifth in the same animal, in as many successive years, then manifestly the preservation of such animal is a most wasteful economy, altogether independently of the danger of her transmitting the infection to healthy stock. If, however, she herself becomes immune after a first or second abortion, it may be profitable to retain her for milk production or breeding, provided that she can no longer infect susceptible cows with which she must come in contact.

Acquired immunity of the individual cow is the rule after one or two abortions caused by the microbes with which we are at present most familiar. There are exceptions to this rule due to special nervousness and excitability of given cows, which tend to an indefinite repetition of the abortion, under the stimulation of pregnancy, of the continued presence of the microbe, or of some local disease (tubercle, tumor, parasite, etc.) of the ovary, womb or peritoneum. Yet statistics show that this only applies to a small proportion of cows and these the most nervous and excitable. The tendency toward insusceptibility to the deleterious action of the germ, which may still be present, is in the cow as a rule greater than the disposition toward a nervous encrease of the susceptibility. The difficulty of reaching a conclusion on this point depends on the fact that stockowners very commonly dispose of aborting cows, and as the freshly bought cows are usually attacked sooner or later, it is too confidently assumed that the old cows also would have continued to abort had they been retained. Many years ago, however, observant New York dairymen had noticed that the same cow rarely aborted over three years in succession, and in the great majority of cases not over two. The owner of a large herd, who has had much experience with the disease, assures me that the rule has been, that a cow did not abort with him a second time. The continuous abortion in a herd was mainly among newly purchased cows and others that had not been previously attacked, including heifers carrying first calf. The same is in a measure true of the European abortions.

Nocard says that after three to five years there is an acquired immunity. Only heifers and the cows that have been recently bought in, abort.

Penberthy, speaking of England, says that in case of repeated abortion in the same cow, the calf is carried longer each successive year until it comes to its full term.

Sand, in his symposium of the experience of Danish veterinarians, says it is quite exceptional that a cow should continue to abort, but outbreaks of abortion disappear spontaneously if no new cows are brought in.

Bang refers to a herd of 200 head of which 83 aborted in their first pregnancy, and of these only 20 aborted in the second, while 7 failed to breed. Counting the latter as having aborted, this amounts to less than one-third, while over two-thirds of the cows that aborted in the first gestation carried the calf to full time.

Paulsen quotes the case of a herd of 16, 7 of which aborted after service by a bull in an aborting herd. One of the seven was sold, but the remaining six all went full time in the following year.