56 



Diagnosis,— KoAid scab can not well be coiifoanded with any other 

 variety of scab. The seat of the disease and the presence of the para- 

 site, which is scarcely visible to the nuaided eye, are snfificient to defi- 

 nitely diagnose the malady. 



Prognosis. — This variety of scab is one of the most amenable to treat- 

 ment. Being mostly on the head it is easy to reach with remedies. If 

 treated it will prove of little loss to the flock-master, while if allowed to 

 take its course it will continue for a long period, gradually growing 

 worse and rendering the patient more and more unsightly and ill-fa- 

 vored. It can cause severe inflammation of the eyes and ears. It can 

 hinder the fattening of the animal and cause extensive alterations of 

 the tissues of the skin. By affecting the health of the sheep, it will not 

 only decrease its weight but materially lessen the amount of wool pro- 

 duced. 



Medical treatment. — The worst feature of treating the disease is, that 

 treatment for a complete eradication seems to be extreme and out of 

 proportion to the end to be attained. Curative treatment always yields 

 good results when the application is rational. In the early stages of 

 the disease, when the scabs are just formed, simple applications of scab 

 dips or ointment are all that are needed; in cases of longer standing it 

 will be found necessary to first soften and loosen the scabs with some 

 kind of grease or oil, and then to remove them with some alkaline solution 

 or soap. The thin oils (sweet oil) that i^enetrate are the best. The wool 

 adjacent to the scabs should be cut away so as to allow the remedies to 

 get at the newly affected ])ortions. 



COMMON SCAB. 



PSOROPTES COMMUNIS, Fiirst., var. ovts. 



Plates VII and VIII. 



Common scab is caused by an insect known as the scab-mite or itch 

 insect— Psoro2)tes communis, Fiirst., var. avis. This insect is much larger 

 than the SarcojJtes, which causes head scab, being-visible to the unaided 

 eye. 



Disease. — Of all the diseases of sheep in this country, scab is the most 

 feared by the flockmaster. So insidious is its attack, so rapid its 

 course, so destructiv^e its effects, and so difficult is it to exterminate 

 that it has justly earned tlie distinction of being, more injurious than 

 any other disease caused by external parasites. Scab alone, of the par- 

 asitic diseases, has become the subject of legislation in most countries, 

 and yet, if i>roper precautions were taken and a rational treatment fol- 

 lowed, this disease could soon be completely eradicated. 



Early symtoms. — Attention to the disease is first attracted by the in- 

 fected sheep scratching, biting, and rubbing themselves. The coats 

 of the animals look rough, taggy, and felted. The itching is always 



