SHEEP SCAB. 13 



which infected sheep have nibbed, oi- from places where they have 

 been. A flock of scabby sheep will infect the roads, trails, sheds, 

 yards, bed grounds, pactures, ranges, and the ground around the 

 watering places. It is therefore important that the flock receive 

 proper treatment as soon as the disease appears, before the infection 

 liecomes scattered over the premises. 



The transmission of the disease to a flock is not limited to any one 

 season of the year, although during the hot summer months few 

 cases of recent infestation are noticed in the range sections. Scab 

 often remains dormant during dry summer months 

 and assumes the appearance of having been cured, 

 but usually becomes evident again with the advent 

 of cold, rainy Aveather. 



Symptoms of scab may develop within a week 

 after healthy sheep have been exposed to it. The 

 usual practice is to consider that the disease may 

 develop at any time within 30 days after exposure, 

 although, under certain conditions, the development 

 may be retarded even longer. The disease develops 

 more rapidly in the fine-wool breeds, such as the ^''"^'- ^^- ~ ^^^i^v 



nr • 1 -r. -n • i louSe {THvlw- 



Merino and Kambouillet, than m the loose-wool iiectes sphwro- 

 breeds having an open fleece, and the fine-wool ccphaius). 

 sheei) also succumb more rapidly to an attack, so '^'^"1* female, 



^ J..' 1 enlarged. 



that treatment must be very carefully applied if the (After g. Neu- 

 results are to be successful. The fle'^ece of the fine- °'''°°' ^^^"-^ 

 wool sheep contains much grease or yolk, which in a measure hinders 

 the penetration of the dip. 



The effect of sunlight on the scab mite is apparently an important 

 factor, since the disease develops most rapidly and is seemingly most 

 severe in its effects on the fine-wool sheep, and is diminished in its 

 effects and retarded in its development in a. direct ratio as the fleece 

 becomes more open. The Navajo Indian sheep, wdiich have very 

 coarse, open fleeces, resembling somewhat that of a goat, rarely if 

 ever are affected with hard scab. While the infection will remain in 

 a flock of such sheep indefinitely if not treated, the lesions seldom 

 become extensive. In the semiarid sheep-ranging sections of the 

 United States it is a well-recognized fact that if scab is to be detected 

 in a flock examination must be made before or at the time of shear- 

 ing. If the scabby sheep in these sections are shorn and turned out 

 on the ranges, where the sunlight is very bright, the scabs dry up, 

 drop off, and the lesions apparently heal. Evidently the infection is 

 not destroyed, but remains dormant, as the disease will as a rule 

 break out again under certain favorable conditions. After the wool 



