THE DOG AS A CARRIER OF PARASITES AND DISEASE. 



13 



by sheep as they graze over range or pasture or drink water con- 

 taminated by these feces. In the sheep the eggshell is digested, the 

 released embryo bores through the tissues and comes to rest usually 

 in the edible musculature, and the bladder worm develops to the 

 cysticercus capable of again infecting the dog. In cases of heavy 

 infestation sheep are liable to die in the course of two to three weeks, 

 but as a rule the health is not perceptibly affected. Here, as in all 

 similar cases, the parasite must pass from the dog to the sheep and 

 from the sheep to the dog. 



Via. 7. — Tapeworm (Tmnia avis) developed l>y feeding bladder worm (Cysticercus ovis) 



to a dog. (From Ransom.) 



The parasite has been found in Europe, Africa, and New Zealand. 

 It lias been found thus far in seven States in this country. It appears 

 to be particularly prevalent in the West, a fact that is possibly re- 

 lated to carelessness on the part of the western sheepmen as regards 

 the disposal of carcasses of sheep <lying on the range. Such sheep 

 are usually Left lying where they die, a practice which aids in the 

 spread and continuance of gid, and which serves the same purpose 

 in the case of the "sheep measles" parasite that throwing diseased 

 viscera of hogs onto the fields does in the ease of the hydatid para- 

 Bite. The sheep dog is probably the principal carrier of the parasite, 



