Parasites and Parasitic Diseases of Sheep. 5 
condition and becoming thin and commonly having a diarrhea or be- 
ing constipated. Other features may be associated with certain 
parasites. Bloodsucking parasites produce anemia, the blood becom- 
ing thin and pale as a result of having too few red blood corpuscles 
for the amount of serum present. Often there is associated with this 
an edema, in which fluid accumulates in the pendant or lower por- 
tions of the body; this is especially prominent in stomach-worm in- 
festation in sheep, the fluid accumulating under the lower jaw and 
giving rise to the so-called “ bottle jaw.” 
In this connection, the advisability of finding out promptly the 
cause of the trouble when sheep become diseased should be empha- 
sized. Curtice has stated the case as follows: 
The sheep owner who discovers weakness among his lambs should not wait 
until one of them dies before he endeavors to make a diagnosis, but should 
undertake to diagnose the disease in the earlier stages by sacrificing one or 
more of the worst affected, and thus gain time in treating and preventing the 
extension of the disease. By waiting for the disease to develop he allows the 
lambs to grow poorer and weaker, and when action is finally undertaken it is 
upon patients which are, in many cases, already too weak to stand vigorous 
treatment and which in no way profit by preventive measures as they should. 
EXTERNAL PARASITES. 
External parasites are those which live on the exterior of another 
animal called the host animal, that is, on the skin or in the layers of 
the skin or in the hair follicles. Internal parasites are those which 
live in the body tissues or cavities of the animal that serves as a host. 
The external parasites of sheep are all arthropods, or animals hay- 
ing 6 or more legs, some of them being insects, which have 6 legs in 
the adult stage, others, such.as mites and ticks, being more closely 
related to the spiders and possessing 8 legs in the adult stage. Some 
of these parasites spend their lives on the sheep; this is true of the 
scab mites and the lice. These are the important forms. Others, 
such as various kinds of biting flies, attack sheep occasionally but 
spend much of their lives off the sheep. 
LICE. 
Location.—Lice live on the skin of sheep, crawling about on the 
wool or hair from place to place and clinging to the wool fibers or 
hairs in feeding. The sucking body louse (Wematopinus ovillus) is 
commonly found in colonies on various parts of the body, including 
_the face. The foot louse (Linognathus pedalis) is usually found on 
the lower portions of the legs, below the true wool and in the short, 
coarse hair. The biting louse (7'richodectes ovis) occurs on various 
parts of the body. 
1Hematopinus ovillus, Linognathus pedalis, Trichodectes ovis (=Tr. spherocephalus). 
