526 



DISEASES OF CATTLE. 



Avith moisture ; that is, during rains, fogs, and dews. When the air 

 becomes dry and the moisture evaporates from the grass the young 

 vrorms cease their activity, resuming their migrations when the air 



again becomes overladen with 

 moisture. Larvae which have 

 developed to the infectious 

 stage, unlike the eggs and 

 early larval stages, are able 

 to survive long periods of 

 freezing and dryness. In two 

 weeks to a month after the 

 embryos are swallowed the}'^ 

 reach maturity and begin 

 producing eggs. 



Preventive treatment. — 

 Preventive measures are im- 

 portant. As moisture favors 

 the development of the em- 

 bryos, high sloping ground is 

 preferable for pastures. If 

 low ground is used, it should 

 be properly drained. The 

 pasture sliould not be over- 

 stocked. Burning over the 

 pasture will destroy most of 

 the young worms on the grass 

 and on the ground, and this 

 means of disinfection under 

 certain circumstances may be 

 very advantageously used. 

 The herd should be changed 

 to fresh pasture as often as 

 possible. Cattle should be 

 supplied with water from 

 wells, springs, or flowing 

 streams, preferably in tanks 

 or troughs raised above the 

 ground. To u slight degree 

 salt serves to protect cattle 

 iigainst infection with internal parasites, and plenty of it should 

 therefore be kept accessible. 



Affected animals should be isolated from the rest of the herd in 

 hospital pens or pastures. A plentiful supply of nourishing feed is 

 an ini})()rtant factor in enabling cattle to withstand the attacks of 

 stomach worms and other intestinal parasites. Tlie stabling of cattle, 



<? 



6 



Fifi. 19. — Twisted stomach worms (Hwmonchus 

 contortus) . Male (o), female (h), and egg (c). 

 Enlai'ired. 



