6 BULLETIN 260, TJ. S. DEPARTMENT OF AGRICULTURE. 



hydatid disease, depending on the location of the parasite. The 

 effects are very serious and the prognosis is always grave. A con- 

 servative estimate gives a death rate of 13.6 per cent of the persons 

 infected (Vegas and Cranwell). The growth of the bladder gives 

 rise to various troubles as a result of pressure, obstruction, perfora- 

 tion of important organs, necrosis of tissue, liberation of poisonous 

 products, secondary bacterial infections, rupture of the hydatid, and 

 secondary hydatid infestation following rupture of the cyst. It is 

 commonly necessary to resort to surgical interference for the re- 

 moval of the hydatid. Operation is often very difficult and may 

 have to be repeated, owing to the presence of small external daughter 

 bladders which are easily overlooked or incapable of detection. A 



Fig. 2. — Portion of a hog's liver infested with hydatid bladderworm (Echinococcus 

 granulosus). Natural size (after Stiles). 



case has been recently recorded where the patient had to be operated 

 on four times before the recurrence due to daughter bladders had 

 ceased. 



In the lower animals hydatids are probably less often a cause of 

 death, owing to the slow growth of the parasite and the fact that 

 the affected animals are likely to be slaughtered before sufficient time 

 has elapsed for the parasite to become a menace to the life of the 

 animal. 



If brood capsules containing the tapeworm heads are eaten by 

 dogs — a thing which is apt to occur on farms where the viscera of 

 slaughtered animals, especially when they appear unwholesome, as 

 they would in hydatid disease, are thrown out on the fields or fed to 



