340 The Diseases of Animals 
There are a number of species of ticks in the South 
that infest cattle and other animals, but this cattle tick 
is the most important. The sheep tick, so called, is not 
a tick, but a fly. It is of a reddish or grayish color, 
about one-fourth of an inch long. It is readily de- 
stroyed by any of the dips which are effective for scab. 
LIVER FLUKES 
Liver flukes (Distoma hepaticum) are small, flat, 
lance-shaped worms, varying in length from one-fourth 
to one-half an inch. The worm attacks cattle, sheep, 
goats and pigs. It is most frequently found in warm, 
moist climates and on low, wet lands where there is 
stagnant water. It usually attacks young animals. 
It causes heavy losses among sheep and calves in some 
countries. It has been estimated that a million sheep 
die annually from this disease. ' It is common in the 
southern part of the United States. An adult fluke, 
infesting the liver of an animal, lays a large number 
of eggs, which pass out with the dung and fall into 
water, where they soon hatch, and attack snails, pass- 
ing one stage of their life-history as a parasite of 
this animal. From the snail, another free-swimming 
form of the parasite escapes, and infests drinking water. 
When these parasites are taken in by a susceptible ani- 
mal they work their way to the liver and there become 
adult parasites. 
In a few cases, in the early stages, an animal may 
die from apoplexy, caused by some of the parasites 
lodging in the brain; but in most cases the symptoms 
