of the disease have been noticed depending upon the season of the 

 year, aggravation in winter alternating with improvement in summer. 



The mite which causes cattle itch, or mange, is closely related to the 

 mite which causes sheep scab; both belong to the same x genus and 

 species, but are different varieties. The sheep-scab mite will not attack 

 cattle, nor will the cattle mite attack sheep or other animals. The 

 itch mites are found to be very numerous upon affected cattle, and a 

 very small quantity of debris from an actively infested area of the skin 

 will often reveal a surprisingly large number of the parasites. These 

 mites may be removed from an animal and retain their vitality for a 

 long time. Specimens have been collected and kept in small glass bot- 

 tles in the laboratory at the ordinary temperature of the room during 

 the winter months, varying from 45 F. during the night to 80 F. 

 during the day, which would live and remain active from eight to 

 eleven days. Exposure to bright sunlight, however, would kill most 

 of the mites in a few hours. 



Scabies does not appear to affect cattle while they are doing well on 

 grass, nor to attack those in good condition over three years old. The 

 animals which suffer most are calves, yearlings, and two-year-olds, and 

 those in poor condition. The first symptom' of the disease is usually 

 an intense itching of the skin about the neck or shoulders, which 

 extends more or less rapidly, depending largely upon the health and 

 vigor of the animal, along the back and sides and down the outside of 

 the legs, but does not usually affect the inside of the legs nor the skin 

 of the abdomen. 



The other variety of this parasite which produces mange in cattie is 

 the Symbiotes. This is known as Symbiotic mange, or tail mange. It 

 remains generally localized upon the depressions on the back part of 

 the croup and at the base of the tail. It may, however, extend over 

 the whole surface of the body if the treatment of the disease and care 

 of the affected animal are neglected. These cases, however, are rare. 

 Foot mange is also exceptional in cattle. Tail mange has almost no 

 spreading tendency, and its contagiousness is hardly noticeable. It 

 yields readily to treatment, and any remedy that will destroy the 

 activity of the parasite producing the Psoroptic, or common form of 

 mange, will readily kill that causing the Symbiotic, or tail mange. It 

 is possible for the different morbid conditions produced by these two 

 varieties of parasites to exist in the name animal at the same time. 



FORM AND LIFE HISTORY OF THE SCAB PARASITE. 



The Psoroptes, the first variety referred to, live upon the surface of 

 the skin, adhere to it, and suck the blood and lymph of the skin by 

 means of their mouth organs, producing a more or less intense inflam- 

 mation through the numerous stings which they inflict. This species 



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