DISEASES OF SHEEP 581 



thrift, disinclination to eat heartily; a paleness about the eyes and 

 lips, yellow tinge in the skin; there may be fullness between the 

 jaws, the wool is dry, brittle and easily pulled. The third stage fol- 

 lows the second and not easily separated from it. The animal loses 

 flesh rapidly, becomes emaciated, the appetite keeps up but the most 

 marked character is the wasting. The fourth stage is that of natural 

 migration of the parasite late in the spring, and spontaneous recov- 

 ery. The sheep as a rule die in the second or third stage if badly 

 infected. (For treatment see liver fluke under Diseases of Cattle.) 



STOMACH WORMS (HAEMONCHUS CONTORTUS) IN SHEEP. 



The stomach worm of sheep, known to zoologists as Hasmonchus 

 contortus, is generally recognized as one of the most serious pests 

 with which the sheep raiser has to contend. Sheep of all ages are 

 subject to infection, and cattle and goats as well as various wild ru- 

 minants may also harbor the parasite. The most serious effects of 

 stomach-worm infection are seen in lambs, while full-grown sheep, 

 although heavily infested, may show no apparent symptoms of dis- 

 ease. It is from these, however, through the medium of the pas- 

 ture, that the lambs become infected. 



Symptoms and Diagnosis. Among the symptoms which have 

 been described for stomach-worm disease probably the most frequent 

 are anemia, loss of flesh, general weakness, dullness, capricious appe- 

 tite, thirst, and diarrhea. The anemic condition is seen in the pale- 

 ness of the skin and mucous membranes of the mouth and eye, and 

 in the watery swellings which often develop under the lower jaw. A 

 more certain diagnosis may be made by killing one of the flock and 

 opening the fourth stomach. The contents of the fourth stomach 

 are allowed to settle gently, and by carefully watching the liquid 

 the parasites, if present in any considerable numbers, will be seen 

 actively wriggling about like little snakes from one-half to 1^ inches 

 long and about as thick as an ordinary pin. They are a blood-red 

 color, due to their habit of sucking blood from the sheep. 



Life History of the Stomach Worm. The worms in the stom- 

 ach produce eggs of microscopic size, which pass out of the body in 

 the droppings and are thus scattered broadcast over the pasture. If 

 the temperature is above 40 to 50 F. the eggs hatch out, requiring 

 from a few hours to two weeks, according as the temperature is high 

 or low. When the temperature is below 40 F. the eggs remain dor- 

 mant, and in this condition may retain their vitality for two or three 

 months, afterwards hatching out if the weather becomes warmer. 

 Freezing or drying soon kills the unhatched eggs. The tiny worm 

 which hatches from the egg feeds upon the organic matter in the 

 manure, and grows until it is nearly one-thirtieth of an inch in 

 length. Further development then ceases until the worm is swal- 

 lowed by a sheep or other ruminant, after which it again begins to 

 grow, and reaches maturity in the fourth stomach of its host in two 

 to three weeks. The chances of the young worms being swallowed 

 are greatly increased by the fact that they crawl up blades of grass 

 whenever sufficient moisture such as dew, rain, or fog is present, 



