PARASITES AFFECTING THE SKIN 27 
Its favourite seat is the head, particularly the upper 
lip, sides of the cheek, and ridge of the nose. The ears 
are less commonly affected. The disease may extend 
down the breast in a bad case. The skin shows a large 
number of vesicles, which burst and discharge a fluid, 
which dries into yellowish crusts. Pruritus is intense, 
and the sheep constantly rub their heads against the 
ground, trees, posts, or their neighbours. The scabs are 
thus torn off, and the bare patches bleed, and crusts of 
congealed blood are left on the face. Conjunctivitis is 
not an uncommon sequel, and may be followed by 
purulent ophthalmia and blindness. The sheep lose 
condition and may cease feeding, while the wool is 
rendered useless. 
The disease is very contagious, and so isolation is a 
matter of great importance, and care must be taken in 
parts where the disease exists not to introduce affected 
animals into a clean flock. 
Treatment.—The scabs must be first softened with 
alkalis, such as liq. potasse, mixed with oils or fats. 
This dressing must then be washed off, and one of the 
following parasiticides applied: Infusion of tobacco, 
sulphur ointment, creolin solution, or diluted tincture of 
iodine. The simplest and most efficacious is the sulphur 
turpentine and oil dressing previously mentioned. 
In this country ‘‘ head mange”’ is not a scheduled 
disease. 
Psoroptic Mange in Sheep (Sheep Scab)—Etiology.— 
The cause is the presence of Psovoptes ovis in the 
fleece. The parasite is usually conveyed to the sheep 
by immediate contact with one previously affected ; 
but as sheep have been known to contract the disease in 
places where there have been no flocks kept for as long 
as one or even two years, it is probable that the parasite 
is able to live for some considerable time apart from 
the host. It is certain that the mites can retain their 
