DIGESTIVE SYSTEM 139 



Icterus, associated with digestive derangement, will probably be 

 the only evidence of the presence of this parasite in any portion of 

 the liver or its excretory duct. 



The location of the parasite prohibits the successful use of 

 therapeutic agents. The possibility of invasion into any of the 

 hepatic structures may be diminished by frequent medication of the 

 swine with agents previously mentioned that will eliminate these 

 parasites from the bowel. Frequent cleaning, and removal of the 

 excrement from the pens, yards, or barns, will tend to diminish in- 

 festation. ■ - 



Distomatosis '' < 



This is a condition resulting from the invasion of the liver by the 

 Distoma hepaticum, Distoma Americanum, or Distoma lanceolatum. 

 All are commonly called flukes. Distomatosis occurs most frequent- 

 ly in animals kept upon low, marshy, or swampy lands. Swine 

 raised in the southern part of the United States are commonly 

 infested. The exact life cycle of these parasites has been carefully 

 worked out and may be obtained by reference to works on para- 

 sites; suffice here to say that the ova are eliminated from the liver 

 in the bile and pass to the outside in the fecal matter. After several 

 changes the embryos are found upon vegetation which is consumed 

 by their hosts. They find their way up the hepatic duct and on into 

 the bile tubes within the liver. 



Lesions. — The lesions established by the different 

 types of Distoma are slightly different. The Dis- 

 toma hepaticum remains for six months in the bile 

 tubes in the liver where it produces obstruction of 

 bile and inflammation of the bile tubes. The ac- 

 cumiilated bile causes distention of the bile tube, 

 which is usually very evident, particularly upom 

 the posterior surface of the liver. The dilated bile 

 fr^^Swr^ tube is found to be thickened and contains thick- 



Fig. 28. Distoma ened flocculent bile and flukes in some stage of 

 a Inte^stines'"' development, depending upon the length of time 



b.' oral sucker. after invasion that the autopsy is conducted. 



a Items'^ sucker. ^-^^ Distoma Americanum either remains in' the 

 bile tubes or passes out into the substance of the 

 liver, where it produces a cyst. The cysts, which attain the size of a 

 hen 's egg, are evidenced by grayish-black elevations upon the surface 



