522 



DISEASES OF CATTLE. 



Fig. 9. — -Screw worm (larva of Chry- 

 somyia macellaria) . (From Bureau 

 of Entomology.) 



The fly also breeds in dead animals, and all carcasses should there- 

 fore be buried deeply or burned. 



Treatment for screw worms. — For proper treatment an animal suf- 

 fering from screw worms should be caught and thrown. Pour chloro- 

 form into the wound, taking care that it penetrates thoroughly into 



all the burrows of the screw worm, 

 if necessary using a slender stick 

 or a small bunch of twisted hay 

 as a probe. The animal should be 

 held for several minutes in order 

 to insure the continued action of 

 the chloroform. Finally the wound 

 should be dressed Avith a carbolic 

 or cresylic ointment to promote healing and thus prevent further 

 infection, or the wound may be painted with pine tar. 



Gbubs, Warbles, Bots. 



The common parasites known as grubs, warbles, bots, etc. (fig. 11), 

 found under the skin of the backs of cattle, where they form more or 

 less conspicuous lumps during the latter part of winter and spring, 

 are the larvae of a fly known as the heel fly or warble fly. This fly 

 {Hypoderma lineata) is about one- 

 half inch long, very haiiT, and 

 somewhat resembles a small black 

 bee in appearance. The flies ap- 

 l)ear early in the summer and are 

 more or less prevalent until the 

 beginning of cold weather. They 

 deposit their eggs on the skin of 

 cattle, fastening them to the hairs. 

 Many eggs are deposited on the 

 heels above the hoofs, hence the 

 name " heel fly." 



Although the flies are unable to 

 bite, cattle seem to be much afraid 

 of them, and apparently are some- 

 times stampeded by them. Either 

 the eggs or the tiny maggots 

 hatching from them are carried into the mouth by the cattle 

 licking themselves. In the former event the eggs hatch in the mouth 

 or in the paunch. In either case the maggots or larvse migrate into 

 the esophagus, or gullet, and penetrate into its walls, where they 

 undergo a portion of their development. From the esophagus the 

 larvae migrate through the tissues of the body toward the back, 

 and according to one investigator enter the spinal canal, where 



Fig. 



niacellaria » 

 mology. > 



Screw-worm fly (Chryaomyia 

 (From Bureau of Ento- 



