556 Cysticercusis uf the Liver. 



ETizootics of eystioereosis of tlie liver have been observed by Kiihnau, Brusa- 

 ferro, Averadere and Moiissu. Similar outbreaks have been described in younjif 

 pigs l)y Diirbeek and Seller. The latter authors have made a special study of the 

 pathological anatomy of the disease. 



Etiology. In cattle and pigs the disease is caused by the 

 Cysticercus tennicollis, which is the cystic stage of the Taenia 

 marginata which inhabits the intestine of the dog (see page 

 468). In rabbits and hares the cause is the Cysticercus pisi- 

 formis, the cystic stage of the Taenia serrata also an inhabitant 

 of the intestine of the dog (see page 468). 



Infection occurs naturally through the ingestion of feces 

 of dogs harboring these parasites. The proglottides or the con- 

 tained eggs are rarely dropped directly into feeding- or drink- 

 ing-troughs. As a rule, the feces are dropped about on the 

 ground or in the neighborhood of drinking places and thus con- 

 taminate the food or water. Pigs may ingest them while root- 

 ing- 



Susceiotibility. It cannot be determined whether there is 

 any difference of susceptibility among animals that harbor the 

 Cysticercus tenuicollis. The varying incidence of the disease 

 in the different species may be due to differences of surround- 

 ings. Age has some influence upon the susceptiliility, since 

 young animals are attacked more frequently and more severely. 

 The fact that animals are affected at the age of a few weeks, 

 shows that within that time the opportunity offers of ingesting 

 the eggs of tapeworms. Young pigs may also ingest the eggs 

 w^hile rooting. 



Pathogenesis. The embryos of the Taenia marginata and 

 T. serrata are liberated from the eggs by the acid stomach 

 contents, and reaching the intestine bore through the Avail and 

 enter the portal veins by which they are carried to the branches 

 of the portal vein in the liver. They have been found there 

 four hours after the ingestion of the eggs (Hoffmann). Some 

 embryos may pass through the capillaries into the hepatic 

 veins, and thus be carried to the lungs or other organs. After 

 their arrest in the blood vessels they bore their way out, and 

 penetrating the liver tissue, make their way to the surface leav- 

 ing tracks behind them. Finally, some of them perforate the cap- 

 sule of the liver and reaching the peritoneal cavity develop 

 further in the omentum, mesentery, or peritoneum. Those that 

 remain under the capsule of the liver also undergo processes 

 of development. The same thing happens to the embryo ar- 

 rested in the vessels of the lungs. 



A severe invasion causes a condition shnilar to that pro- 

 duced by a heavy infestation wdth flukes (see page 549). There 

 is an acute hepatitis often associated with hemorrhage and a 

 localized or wide-spread peritonitis. The rupture of large ves- 

 sels may cause fatal hemorrhage. If the animals survive, the 

 acute liepatitis is followed by an interstitial inflammation, 



