SPREAD OF TUBERCULOSIS AMONG HEALTHY CATTLE UPON EXPOSURE TO TUBERCULOUS CATTLE.

By E. C. SCHROEDER, M. D. V., and W. E. COTTON,

Superintendent and Expert Assistant of Experiment Station of Bureau of Animal Industry. A number of investigations have already been made regarding the rapidity with which tuberculosis spreads among healthy cattle, under various conditions, when exposed in stalls and stables previously occupied or occupied at the same time by cattle affected with tuberculosis. These investigations have generally shown that the introduction of a tubercular animal into a healthy herd will, in all probability, be followed by serious consequences in a comparatively short period of time. In fact, a healthy herd of cattle, through the introduction of a tubercular cow, in the light of the following experiment and the investigations above referred to, may in less than a single year become entirely tubercular. The importance of this fact not only in its simple economical bearing on the cattle industry, but also on the public health, is so great that it can hardly be sufficiently accentuated. This is especially true when the subject is contemplated in connection with the now well-established reputation of tuberculin as a diagnostic agent in tuberculosis, and the knowledge that, through the proper use of tuberculin, healthy herds of cattle can almost with absolute certainty be protected from exposure to tubercular cattle, and tubercular cattle can readily be separated from other cattle which have not yet become affected.

On January 27, 1903, in the following experiment 7 healthy cattle and 3 tubercular cows were confined in a stable containing 10 box stalls. The stalls were separated by solid 2-inch plank partitions, 6 feet high. Five of the healthy cattle and the 3 tubercular cows occupied different stalls each day, in a rotation which exposed each of the healthy cattle equally to the 3 tubercular cows. Two of the healthy cattle occupied stalls near the center of the stable and were at no time allowed to enter other stalls or to come into closer contact with any of the other cattle. On April 10, 1903, 1 of the 3 tubercular cows was removed from the stable, and 2 other and more severely affected cows were introduced. On June 12, 1903, 1 of the latter died and was found on autopsy to be affected with generalized tuberculosis; however, without disease of the udder or lymph glands associated with or near the udder. Eight guinea pigs which were fed the milk of this cow from

April 6 to June 8 were killed about two months after the feeding ceased and were found to be unaffected. Three guinea pigs received on April 15, 1903, each an intraabdominal injection of 5 c. c. of milk from this cow. Two of the guinea pigs died, respectively, on June 11 and June 29, affected with generalized tuberculosis, and the third was killed on September 4, 1903, and was found to be fat and free from all lesions of disease.

The 4 other tubercular cows used in the experiment are alive at this time [November 7, 1903]. Guinea pigs fed the milk of these cows remained healthy, and the same is true of guinea pigs which received intraabdominal injections, with the exception of the milk from 1 cow, which on injection caused generalized tuberculosis in 2 of 3 guinea pigs. The latter cow was one of the 2 introduced into the stable on April 10. The other 3 cows were so slightly affected with tuberculosis that the presence of the disease would have escaped the casual observer. A record of the exposed cattle follows:

Bull No. 263, yearling; in good condition; tested with tuberculin without reaction,

January 27, 1903.-Placed in stable with tubercular cattle. Occupied a stall about the center of the stable, which was separated from the other stalls by a 6-foot-high solid 2-inch plank partition. At no time did he enter a stall which had been previously occupied by a tubercular animal.

June 30, 1903.—Tested with tuberculin and gave a reaction which reached 3.6° F., at its highest point. a General condition, excellent.

August 3, 1903.-Killed and examined postmortem. Autopsy record follows: General condition, excellent. Posterior mediastinal glands are slightly enlarged and contain numerous small recent foci of tuberculosis. The anterior mediastinal glands are greatly enlarged and are filled with foci of tubercular material. Bronchial glands contain several small foci of recent tubercular disease.

Cow No. 257, about six years old; in good condition; tested with tuberculin without reaction.

January 27, 1903.-Placed in stable with tubercular cattle. Occupied a stall about the center of the stable, which was separated from the other stalls by a 6-foot-high solid 2-inch plank partition. At no time did she enter a stall which had been previously occupied by a tubercular animal.

June 25, 1903.-Produced a healthy female calf.

June 30, 1903.-Tested with tuberculin without reaction. August 3, 1903.—Killed and examined postmortem. Autopsy record follows: Several of the mediastinal glands are greatly enlarged and thickly sprinkled with small tubercular nodules, which are recent in character. Several small recent areas of tubercular disease sprinkled through the lung. The liver is adherent to the diaphragm in several places by bands of firm, white connective tissue. No tubercular lesions in the liver or portal glands. The right hind quarter of the udder is indurated, and the proper secreting tissue has been replaced by a thick, dense network of connective tissue supporting small masses of fat. This quarter of the udder secreted practically no milk. The other quarters of the udder healthy. The disease of the

a The amount of reaction in all these cases is determined by subtracting the highest temperature on the day before injection with tuberculin from the highest temperature on the following day.

udder was not of a tubercular character. As this cow gave no reaction when she was tested with tuberculin a little over a month before her death, it was believed wise, notwithstanding the typical character of the tubercular lesions in the mediastinal glands and lung, to confirm the diagnosis by guinea-pig injection; hence, 2 guinea pigs were inoculated with small fragments of tubercular material from the mediastinal glands. One of the guinea pigs died two months after the inoculation, affected with generalized tuberculosis; and the other guinea pig was killed two months after the inoculation and found to be affected with generalized tuberculosis. The calf of cow No. 257 was killed on August 3, 1903, and careful examination failed to show any lesions of disease whatsoever. The failure of this cow to react when tested with tuberculin on June 30 may be due to the fact that she produced a calf only five days before the test was made.

Heifer No. 293, about eighteen months old; in good condition; tested with tuberculin without reaction.

January 27, 1903.-Placed in stable with tubercular cattle, and made to occupy a different stall each day, together with a number of other cattle, which caused her to be exposed equally with the other cattle to several tubercular cows.

June 30, 1903.-Tested with tuberculin and gave a reaction which reached 2.8° F. at its highest point. General condition of heifer is very good.

August 3, 1903.-Killed and examined postmortem. Autopsy follows: One small focus of tubercular disease in the center of the left principal lobe of the lung. Several of the pharyngeal glands show patches of reddening, but no well-defined lesions. Sprinkled over various portions of the pulmonary pleura of the right principal lobe of the lung are numerous minute tubercles and groups of tubercles; corresponding tubercles are present on the costal pleura. The pulmonary surface of the diaphragm is sprinkled with numerous small tubercles and groups of tubercles, and the various lobes of the lungs are adherent to each other and the diaphragm by means of tissue thickly sprinkled with tubercles. The lesions had the typical character of pearl disease in cattle.

Heifer No. 296, about six months old; in good condition; tested with tuberculin without reaction.

January 27, 1903.-Placed in stable with tubercular cattle and exposed by moving from stall to stall in the same manner as heifer No. 293.

June 30, 1903.-Tested with tuberculin and gave a reaction which reached 2° F. at its highest point. General condition is good.

August 5, 1903.-Killed this date and examined postmortem. Autopsy record follows: The left principal lobe of the lung is adherent over a small area to the chest wall; near the adhesion is a tubercular nodule in the lung tissue about 1 inch in diameter. The mediastinal glands, posterior and anterior, the bronchial glands, and the lymph glands about the root of the tongue are greatly enlarged, and either entirely tubercular or thickly sprinkled with minute tubercular foci. Several of the mesenteric lymph glands are converted, to the extent of one-half their entire substance, into tubercular material, and a number of other mesenteric glands show small tubercular foci. Glands at the brim of the pelvis in the abdominal cavity show tubercular lesions. The lesions all are of comparatively recent character, and show no tendency to break down or soften.

Bull calf No. 255, about six months old; tested with tuberculin without reaction; in good condition.

July 12, 1902.—Injected into right jugular 20 c. c. of dead human tubercle culture. The culture was grown in the biochemic laboratory of the Bureau of Animal Industry, and was marked No. 59, meaning that it was of the fifty-ninth generation grown

on artificial culture media. The culture was killed at the Experiment Station by exposing it to a temperature of 98° C. for one hour. Two guinea pigs were injected with a portion of the dead culture and were killed two and one-half months later, and were found to be in excellent condition and free from all lesions of disease. The injection of the calf was followed by no adverse condition.

January 27, 1903.-Tested with tuberculin without reaction, and was afterwards placed in stable with the tubercular cattle and exposed by moving from stall to stall in the same manner as heifer No. 293.

June 30, 1903.-Tested with tuberculin, and gave a reaction which reached 2.6° F. at its highest point. General condition is good.

August 6, 1903.-Killed this date and examined postmortem. Autopsy record follows: The thoracic walls and the surface of the diaphragm where the lung rests against it are covered with minute shreds of fibrous exudate of a pale-red color. The lung is adherent to the chest wall and the diaphragm in several places. In the mediastinal glands are a number of tubercular foci; the foci in the anterior are somewhat larger and more numerous than in the posterior glands. The lymph glands back of the pharynx are five times their normal size and completely tubercular. In the liver are a number of small recent foci of tuberculosis. The portal glands are sprinkled with minute hemorrhagic points, but show no lesions of tuberculosis. Two guinea pigs were inoculated with tubercular material from this animal, and both died about two months later affected with generalized tuberculosis. The object in making the guinea-pig injections was to remove any suspicion which might exist regarding the possibility that the extensive characteristic tubercular lesions could have been caused by the intravenous injection of dead tubercle germs made on July 12, 1902.

Heifer calf No. 261, about four and one-half months old; tested with tuberculin without reaction; is in good condition.

July 19, 1902.-Injected into right jugular 20 c. c. of dead bovine tubercle culture. The tubercle culture was grown in the biochemic laboratory of the Bureau of Animal Industry, and was marked Bovine III, 37. The culture was killed at the Experiment Station by exposing it to a temperature of 98° C. for one hour. Two guinea pigs were injected with a portion of the dead culture, and were killed two and one-half months later, and were found to be in excellent condition and free from all lesions of disease. In the calf the injection was followed by no symptoms of disease.

January 27, 1903. -Tested with tuberculin without reaction, and was afterwards placed in stable with tubercular cattle and exposed by moving from stall to stall in the same manner as heifer No. 293.

June 30, 1903.-Tested with tuberculin, and gave a reaction which reached 3° F. at its highest point, notwithstanding that its temperature on the day before injection with tuberculin was quite high.

August 5, 1903.-Killed this date and examined postmortem. Autopsy record follows: At the seat of the intrajugular injection of dead bovine tubercle culture is a small abscess about 14 inches in diameter, which contains soft, creamy pus. Several of the mediastinal glands and the bronchial glands contain each from one to six tubercular foci. One mesenteric gland contains one tubercular focus one-fourth inch in diameter. Two guinea pigs were inoculated with small fragments of tubercular tissue from this animal, and 1 died about two months later and the other was killed

a When intravenous injections are made of either dead or living, human or bovine tubercle cultures, an abscess of the kind here described is almost certain to develop if any portion of the culture leaks from the vein or the syringe into the surrounding tissue. Hence, in this case, when the sterility of the culture used was tested on guinea pigs the lesion has no particular significance.