GHAPTEB XX. 



EXTERNAL AND INTERNAL PARASITES OF 

 ANIMALS. 



Parasitic troubles are numerous among the stockman's 

 charges, and are in many cases hard to overcome, horses, 

 sheep and poultry seem to be more commonly affected 

 than cattle and pigs. In order to render the study of 

 these parasites easier, they will be classified into (A) ex- 

 ternal, (B) internal. 



(A ) External parasites cause such diseases as scab in 

 sheep, mange in horses and dogs, lice of all farmstock, 

 including poultry, the warbles of cattle, ringworm of 

 cattle and grease of horses. 



Scab is a disease of sheep, caused by one of the mange 

 parasites (sarcoptes ovis), and is transmitted by contact 

 from one sheep to the other. Eange sheep are more com- 

 monly affected than those kept on the farms, although 

 the recent laws and systematic dippings are tending to 

 stamp it out. Sheep affected with this disease do not 

 thrive, they are continually rubbing themselves, due to 

 the itching caused by the parasite (scabmite), the wool 

 falls out, leaving large, bare, raw spots, and often forma- 

 tion of scabs and tagging of the wool, later the skin be- 

 comes furrowed and thickened and bleeds from the 

 cracks. The best treatment is preventive in character. 

 Dip all sheep before putting with the flock; affected 

 sheep should be kept from healthy sheep, and dipped a 



