AXIMAL PARASITES OF CATTLE. 



521 



the air is saturated with moistuie; that is, during rains, fogs, and 

 dews. Wlien the air becomes dry and the moisture evaporates from 

 the grass the young worms cease their activity, resmiiing their migra- 

 tions when the air again becomes overladen with moisture. Larva> 

 which have developed to the infectious stage, unlike the eggs and 

 early larval stages, are able to survive long periods of freezing and dry- 

 ness. In two weeks to a month after the embryos are swallowed they 

 reach maturity and begin producing eggs. 



Preventive treatment. — Preventive measures are important. As 

 moisture favors the development of the embryos, high sloping ground 

 is preferable for pastures. If low ground is 

 used, it should be properly drained. The pas- 

 ture should not be overstocked. 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 cir- 

 cumstances may be very advantageously used. 

 The herd should be changed to fresh pasture 

 as often as possible. Cattle should be sup- 

 plied with water from wells, springs, or flow- 

 ing streams, preferably in tanks or troughs 

 raised above the ground. To a slight degree 

 salt serves to protect cattle against 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 pas- 

 tures. A plentiful supply of nourishing feed 

 is an important factor in enabling cattle to 

 withstand the attacks of stomach worms and 

 other intestinal parasites. The stabling of 

 cattle, with the maintenance of clean and 

 sanitary surroundings and liberal feeding, 

 ■\nll often stop losses from internal parasites, 

 even though no medicinal treatment is given. 



MHlicinal treatment. — In dosing animals for stomach worms it is 

 advisable to treat not only the animals which are seriously affected, 

 but the rest of the herd as well, since the parasites ^^'ith which thev 

 are infested will remain as a source of reinfection to the others. The 

 cattle should be removed to fresh pasture after treatment, if possible. 



The annuals to be treated should be deprived of feed for 12 to 16. 

 or even 24, hours before they are dosed, and if the bluestone treat- 

 ment is used should receive no water on the da}' they are dosed until 

 several hom-s after dosing. In drenching, a long-necked bottle or a 

 drenching tube may be used. h\ case the former is used the dose 



0.1 inm 



Fk;. 1.'>.— Larva of twisted stom- 

 ach worm {Hxmonchus contur- 

 tus) coiled on tip of grass blade. 

 Enlarged. 



