Parasites and Parasitic Diseases of Sheep. 9 
Distribution.—Sheep ticks are widely distributed over the world 
and are common in the United States on both farms and ranges. 
Where dipping of range sheep for scab has been practiced it has 
kept down the sheep tick, but where it has ceased sheep ticks have 
become very prevalent. They are most common on coarse-wool and 
medium-wool sheep, and prefer the neck, breast, shoulders, belly, 
and thighs. : 
Symptoms and lesions.—The damage done by the sheep tick is of 
two kinds. It is a bloodsucker, thus causing great irritation, loss of 
blood, interference with feeding, and consequently poor nutrition 
and reduced vitality. It lives in the wool and lowers the value of 
the wool by soiling it 
with the excreta and 
with the pupal cases. 
The loss caused is in 
addition to the wool 
deterioration which 
results from the in- 
jury to the sheep it- 
self. The ticks may 
be easily found on 
parting the wool. 
Their presence may 
be suspected when 
sheep bite, scratch, or 
rub, and show a rag- 
ged fleece as a result. 
Treatment.—The 
treatment for ticks is 
dipping. The coal-tar 
creosote, cresol, nico- 
tin, and the lime-sul- 
phur-arsenic dips are all satisfactory, but dips containing arsenic are 
not desirable for sheep. Dip twice at a 24- to 28-day interval. 
Prevention.—All places which have been occupied by ticky sheep 
should be regarded as dangerous from this standpoint for a period 
of two months, as the pupe# may retain their vitality under certain 
conditions for almost this length of time. Usually pupz remain in 
the wool, but wool containing pupe may be rubbed off or pulled off 
and young ticks hatching from such pupze may afterwards get on 
sheep. If inclosures are to be used for clean sheep within this 
period they should be thoroughly cleaned and the litter and manure 
disposed of in such a way that sheep can not come into contact with 
them until after the lapse of the 60-day period. <A strong solution 
184550°—20-—2 
Fie. 4.—Sheep tick (Melophagus ovinus). Engorged female, 
enlarged. (Irom Imes, 1917.) 
