502 IOWA DEPARTMENT OF AGRICULTURE. 



PARTS OF BODY AFFECTED BY SCAB. 



When sheep are kept in large numbers the chances for infection are 

 naturally greater and the disease may begin on almost any part of the 

 body. Generally, however, it affects the parts which are covered with 

 wool. When the sheep are fat and the wool has a large amount of yolk, 

 the progress of the disease may be slow; usually beginning on the upper 

 part of the body, withers, and back; it extends slowly, but none the less 

 surely, and in ever-increasing areas, to the neck, sides, flanks, rump, etc. 

 In two or three months the entire body may be affected. 



CONTAGIOUSNESS OF SCAB. 



Common scab is exceedingly contagious from one sheep to another, and 

 may in some cases show itself within about a week after healthy sheep 

 have been exposed to infection. The contagion may be direct, by contact 

 of one sheep with another; or indirect, from tags of wool or from fences, 

 posts, etc., against which scabby sheep have rubbed, or from the places 

 where the sheep have been "bedded down." One attack of scab does not 

 protect sheep from later attacks. Transmitted to man, sheep scab may 

 produce a slight spot on the skin, a point which is sometimes taken ad- 

 vantage of for the purpose of diagnosis. In case of suspected scab, one of 

 the crusts is bound lightly on the arm. After a short time an itching 

 sensation is felt and the mites are found on the skin. Transmitted to 

 horses, cattle or goats, common sheep scab fails to develop. 



CHANCES FOR RECOVERY FROM SCAB. 



Cases of apparent spontaneous recovery are rare. Usually when proper 

 methods of treatment are not adopted the disease increases, leads to 

 anaemia, emaciation, exhaustion and death and may result in a loss of 

 from 10 to 80 per cent of the flock. Scab is favored by season when the 

 wool is longest, and by huddling or overcrowding the animals; also race, 

 energy, temperament, age, state of health, length, fineness and abundance 

 of wool, and the hygienic conditions of the surrounding influence the 

 course and termination of the disease. Young, weak, closely inbi'ed ani- 

 mals and those with long, coarse wool will most quickly succumb. Un- 

 healthy localities, damp climate and poorly ventilated sheds favor the 

 disease. Pure or mixed Merino sheep succumb sooner than certain other 

 breeds. The mortality varies according to conditions, but is highest in 

 autumn and winter. When owners are careless the death rate may be 

 very high; if untreated the sheep may die in two or three months. Hy- 

 gienic conditions, good food, and cool, dry atmosphere tend to check the 

 disease. Sheep sheds should accordingly be well ventilated and open to 

 light and sunshine. With proper attention to hygienic conditions and 

 thorough dipping a positive cure can be guaranteed. 



VITALITY OF THE SCAB PARASITE. 



Taken from the sheep, the mites possess a remarkable vitality. It is 

 generally stated that, kept at a moderate temperature on portions of scab, 

 the adults may live from four to twenty days, but they will occasionally 

 live much longer; cases are on record where they have lived three, four 



