190 COMMON AILMENTS OF CATTLE 



develops very slowly and for this reason many owners of cattle 

 do not suspect its presence in their herd until several animals 

 have become diseased. If tuberculosis were rapid in its develop- 

 ment and caused death within a few days like some of the other 

 infectious diseases of cattle, rigid measures would soon be 

 adopted in order to check its progress and dissemination. In 

 many parts of our country it is customary to allow hogs to feed 

 in the dung of cattle. If the cattle be tuberculous, their manure 

 will quite often be laden with virulent germs which, when 

 taken up by the swine, cause them to become diseased. Especially 

 is this so in herds where the disease has become extensive. 

 Tuberculosis is not hereditary, but the offspring of tuberculous 

 parents acquire a predisposition to the disease; i.e., they are 

 more apt to become affected with tuberculosis when exposed to 

 the infection than are the young born from healthy parents. 



Symptoms. — The symptoms or signs of tuberculosis are 

 numerous and while some of them are quite suggestive of tuber- 

 culosis, not one can be relied upon with any great degree of 

 certainty in the establishment of a diagnosis. In some infectious 

 diseases, certain symptoms occur which are characteristic of 

 that disease alone. Characteristic symptoms or signs are not 

 observed, however, in tuberculosis. Tuberculosis may be pres- 

 ent in fat, sleek-looking cattle which show no symptoms of ill 

 health (Fig. 66). Such cases can be detected by the tuberculin 

 test only. The symptoms of tuberculosis vary according to the 

 organ affected. In some instances unthriftiness and loss of 

 flesh will be the chief symptoms observed (Fig. 67). When the 

 lungs are diseased a rather weak, subdned, infrequent cough 

 will be noticed. This cough is most severe in the early morn- 

 ing or after exercise, and after drinking, respiration becomes 

 more difficult and at times quite rapid. The appetite gradually 

 decreases and intestinal derangement develops. When the in- 

 testines are diseased diarrhoea is a prominent symptom. En- 

 largement of the superficial lymph glands in the region of the 

 throat and neck are of frequent occurrence. When the glands 

 of the chest become enlarged, sufficient pressure is at times 

 exerted on the gullet or oesophagus to cause the animal to suffer 



