68 SWINE DISEASES 



Lesions. The lesions established by the different 

 types of Distoma are slightly different. The Distoma 

 hepaticum remains for six months in the bile tubes in 

 the liver, where it produces obstruction of bile and inflam- 

 mation of the bile tubes. The accumulated bile causes 

 distention of the bile tube, which is usually very evident, 

 particularly upon the posterior surface of the liver. The 

 dilated bile tube is found to be thickened and contains 

 thickened flocculent bile and flukes in some stage of 

 development, depending upon the length of time after 

 invasion that the autopsy is conducted. 



The Distoma Americanum either remains in the bile 

 tubes or passes out into the substance of the liver, 

 where it produces a cyst. These cysts, which attain 

 the size of a hen's egg, are evidenced by grayish-black 

 elevation upon the surface of the liver. The cysts 

 contain a chocolate-colored fluid and one or more dis- 

 tomes. 



The Distoma lanceolatum produces lesio/is similar to 

 those produced by the Distoma Americanum. The 

 latter parasite is easily distinguished from the former by 

 its large size and its distinctive shape. 



A liver in which the Distoma have developed and 

 disappeared contains cicatrices or areas of necrotic 

 calcareous material, evidences of the parasitic invasion. 



Symptoms. It is difficult to diagnose hepatic 

 distomiasis by the clinical symptoms. The history of 

 the case, particularly the source of the animal affected, 

 should be given proper consideration. The symptoms 

 vary according to the intensity of infestation, and do 

 not appear for from one to two months after infestation. 

 There is more or less icterus, digestive derangement, 

 unthriftiness, and emaciation. The disease may terminate 

 fatally and it may be quite widespread, affecting a large 

 percentage of swine in the Southern States, particularly 

 during wet seasons. 



Treatment. Treatment is of no avail. Invasion 

 may be diminished or entirely prevented by keeping 

 swine out of pens, yards, and pastures where previous 



