528 DISEASES OF SWINE 



disease causes such slight manifestations that owners of swine are 

 so negligent in attempting to check the spread of tuberculosis 

 among swine. At the packing houses some of the most marked 

 cases of the disease are seen in hogs that are large, fat, and 

 apparently in the very best of condition. In fact, it seems that 

 during the first few weeks or months of the disease the presence 

 of the toxic substances produced by the germs act as a bitter tonic 

 to the system of the hog and cause it to thrive particularly well. 



In those cases where evidences of the disease are noticeable, they 

 consist principally of a general appearance of unthriftiness. This is 

 a symptom of a number of diseases, and does not mean very much 

 from a diagnostic standpoint. If the disease advances rapidly and 

 becomes generalized, more marked symptoms may appear. In 

 those cases that involve principally the abdominal cavity the 

 symptoms will show loss of appetite, digestive disturbance, consti- 

 pation, and diarrhea. Persistent coughing of a harsh, dry character 

 is the most prominent symptom of a tuberculous infection of the 

 lungs. Cough in hogs that are kept in improper surroundings, and 

 especially with overheating and overcrowding at night, is not un- 

 common, and may or may not mean tuberculosis. Infestation of 

 the lungs with the lung worm also produces a harsh, dry cough, and 

 the condition so developed cannot be reasonably distinguished 

 from tuberculosis. 



Where the disease becomes well generalized, and affects both 

 the lungs and the digestive organs, more marked suggestive symp- 

 toms may develop. In addition to the cough and interference with 

 respiration and the digestive disturbances there is noted a loss of 

 weight and energy. The hog so affected does not do well and be- 

 gins to loose its usual vigor and activity. It eats poorly, may have 

 alternating periods of diarrhea and constipation, and becomes easily 

 exhausted. Such cases as these can be sometimes diagnosed with 

 a fair degree of certainty as tuberculosis. Such plainly marked 

 cases are, however, very unusual, and even the most expert can 

 seldom make a diagnosis of the disease in the living hog except by 

 the use of a special diagnostic method, known as the tubercuHn 

 test. This tubercuhn test has been extensively used in cattle and 

 in man with most pleasing results. In the hog it is not quite so 

 •dependable, especially when given by the subcutaneous method. 



