SHEEP SCAB. 
Clarence P. Gillette, M. S. 
The diseases known as “scab’^ in sheep, “itch” in man and 
“mange” in cattle, horses, dogs and other animals are caused 
by minute animal parasites that feed upon or just beneath the 
surface of the skin. 
These parasites are spider-like in structure and belong to 
the true mites, which differ from spiders in being, for the greater 
part, minute in size, in having but six legs when young, and in 
having the three parts of the body, head, thorax and abdomen, 
all united in one. (See figure 1.) 
Although the different species of mange mites look very 
much alike, it is seldom that a species that infests one kind 
of animal will live upon any other. The species [Psoroptes com- 
munis) that causes common scab of sheep is known to infest 
horses and cattle, though it seldom thrives well upon them. 
Common scab has long been considered one of the worst 
maladies that sheep are subject to in this country, and it has 
also attracted a large amount of attention in Europe and Aus- 
tralia. As the parasites readily spread from sheep to sheep, 
the disease is properly considered a contagious one and rigid 
quarantine laws have been enacted nearly everywhere that the 
disease prevails to prevent, as much as possible, its spread into 
uninfested localities. 
Sheep-feeding has become a very important industry in Colo- 
rado during the past few years. Hundreds of thousands of 
iambs are fattened for the eastern markets during the winter, 
and nearly all require to be dipped for scab. There is a wide 
diversity of opinion among feeders as to the best dips to use 
and as to the best methods of handling the flocks to prevent 
or cure scab, and it was with a view of settling, or, at least, 
throwing some light upon these questions, that the experiments 
and observations reported in the following pages were under- 
taken. The work has only been in progress during the past 
winter and spring and is nec€‘ssarily incomplete. In fact, the 
present paper should be considered as a progress report rather 
than a report upon a finished work. I hope, next fall and win- 
