266 INSECTS AFFECTING DOMESTIC ANIMALS. 
Foor SCAB OF SHEEP. 
This variety of scab, which is due to Chorioptes symbiotes Verheyen, var. ovis, is 
of rare occurrence. It has been noticed and studied in Germany by Zurn. 
The seat of the disease is in the feet and limbs. The disease progresses very 
slowly from the feet, and little by little invades the upper part of the limbs and 
adjeining parts. It is not readily communicable to other sheep, and spreads slowly. 
In the beginning this variety of scab is characterized by the reddening, followed 
by the abundant scaling of the skin, and later by yellowish white crusts. The 
animals stamp, scratch, and bite the parts, showing an intense itching. As the dis- 
ease progresses the crusts become thicker, cracks form in the folds of the pastern, 
and the limbs become quite unsightly. The parasitesswarm beneath the crusts, and 
when found form a certain symptom of the character of the disease. 
Foot scab is not a serious malady, as it readily yields to treatment and is slow of 
extension. Any of the remedies proposed for the treatment of common scab may be 
used with good effect. (Curtice.) 
THE ScAB MITE OF SHEEP, HORSES, AND CATTLE.! 
Psoroptes communis Furst. 
1} 
The disease known as scab of sheep is among the few parasitic dis- 
eases which is fully appreciated by the majority of sheep breeders, so 
well known, indeed, that many of the States have stringent laws in 
force for its quarantine or extermination. Curtice says: 
Of all the diseases of sheep in this country scab is the most feared by the flock 
master. So insidious is its attack, so rapid its course, so destructive its effects, and 
so difficult is it to exterminate that it has justly earned the distinction of being more 
injurious than any other disease caused by external parasites. Scab alone of the 
parasitic diseases has become the subject of legislation in most countries, and yet, 
if proper precautions were taken and a rational treatment followed, this disease 
could soon be completely eradicated. 
The earlier writings upon the disease do not give us definite infor- 
mation as to the parasite in hand, but in 1841 Gervais (Ann. Soe. Nat.) 
gave the species a scientific description under the name of Psoroptes 
equi, and the later publications of Gerlach, Furstenberg, Murray, and 
Mégnin contain detailed discussions of its habits, anatomy, etc. 
ScAB MITE OF SHEEP. 
(Var. ovis.) 
This is the variety which produces the best known form of disease; 
indeed 1t appears that the effects of this parasite are by no means so 
much dreaded upon the other hosts, either because those animals are 
not so seriously influenced by its presence or because their skins do not 
'There has been considerable confusion with regard to the name of this species, 
partly owing to the fact that some authors have given a name for each form occur- 
ring on the horse, sheep, and cow, partly because the earlier names have not been 
respected by later writers. The names adopted here are the ones that seem to be 
the rightful ones, taking the first for the species as a whole and using the varietal 
names to indicate the host animal. 
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