Parasites and Parasitic Diseases of Sheep. 7 
Distribution.—Biting lice are rather common in the United States. 
The sucking body louse is fairly common on sheep in the Southwest. 
The foot louse has been found on sheep in various parts of the 
country. 
Symptoms and lesions.—Lice, whether biting lice or sucking lice, 
cause itching and irritation. This of itself interferes with nutrition, 
and affected animals fail to fatten or keep in condition as they 
should. Moreover, the itching leads to scratching, with a resultant 
loss of wool, and this scratching adds more time lost from feeding 
to that lost from discomfort. Scratching may also cause cuts and 
bruises. The loss of nervous energy and the interference with feed- 
ing and nutrition tend to stunt the growth of young animals, inter- 
fere with the fattening of the entire flock, and predispose to other 
diseases by lowering the vitality. Actual lesions in the form of 
sores are caused where numerous biting lice 
cluster. The sucking lice abstract blood and 
lymph in considerable quantities where the 
lice are numerous. Finally, the excreta of the 
lice soil the wool, sometimes to a considerable 
extent; this is particularly true of the sucking 
body louse. 
Lice are readily found on infested animals 
by examining them carefully, preferably in 
direct sunlight. 
Treatment.—Where sheep are infested with Fic. 3.—Sheep louse 
(Trichodectes ovis). 
biting lice only, sodium fluorid may be ap- Adullstamalevenlarzed. 
plied in the form of a powder to get rid of este AN eae ey 
892.) 
them, a single application sufficing for this 
purpose. The powder is rubbed into the skin at a number of places 
so as to insure a good distribution. It is of no value against sucking 
lice. 
For sucking lice it is necessary to use a contact poison, and these 
poisons are also satisfactory for biting lice. In cold weather, where 
dipping is inadvisable, insect powders, composed largely of pyreth- 
rum and naphthalene, may be used as a control measure and will 
serve to control the lice, but are not satisfactory in eradicating them. 
For dipping, the substances which have been found effective in 
field tests are coal-tar creosote, cresol, arsenical dip, and 0.07 per 
cent nicotin solution with 2 per cent flowers of sulphur. To eradi- 
cate lice it is usually necessary to dip at least twice, with an interval 
of 14 to 16 days between dippings, in order to kill the lice that hatch 
out after dipping, since these dips can not be depended upon to kill 
all the eggs or “nits.” Spraying is generally unsatisfactory as a 
method of applying dips to sheep, as it is too difficult to wet the wool. 
