374 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



the decreased vigor and lessened vitality of the affected animals favor 

 more rapid multiplication of the mites and the further extension 

 and intensification of the disease. Thus we have cause and effect 

 working together, with the result that scabies, or mange, of cattle 

 may in some cases prove fatal ; especially are fatal terminations likely 

 to occur in the latter part of a severe winter among immature and 

 growing animals, or those of adult and full age when in an unthrifty 

 condition at the time of becoming affected. Variations in the prog- 

 ress 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 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 para- 

 sites. 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 bottles in the laboratory at the ordinary temperature of 

 the room during the winter months, carrying 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, how- 

 ever, 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 in- 

 side of the legs nor the skin of the abdomen. 



The other variety of this parasite which produces mange in 

 cattle 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, how- 

 ever, 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 contagious- 

 ness 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 same 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 



