BIGHEAD OF SHEEP 301 



Etiology. — ^The cause of bighead has not yet been deter- 

 mined. Outbreaks occur usually during the spring and early 

 summer while the sheep are being driven from the winter to 

 the summer ranges and before they are sheared. Climatic 

 conditions evidently predispose to the disorder, which is most 

 apt to appear following a cold, stormy night, especially if the 

 sheep are driven the next day in the hot sunshine. The dis- 

 ease is most apt to affect adult sheep; it is rarely seen in 

 young lambs. The condition of the sheep seems to have little 

 to do with the occurrence of an outbreak; it is as apt to 

 attack the well nourished as it is iridividuals poor in flesh. 

 Buckwheat feeding has failed to produce in experimental 

 animals sjonptoms of the disorder. 



Symptoms. — ^The symptoms which precede the appearance 

 of the swellings are jerking movements of the head; the sheep 

 shakes its head and rubs it against objects. The eyesight 

 seems to be impaired, the sheep often running into other 

 sheep and objects found in its path. Symptoms of cerebral 

 excitement are not uncommon, in some instances the sheep 

 show maniacal phenomena. Obviously sheep so affected 

 often leave the flock, become lost, and die of exhaustion and 

 exposure, or become the prey of coyotes. 



Later it will be noted that the ears begin to turn red and 

 become swollen. Finally the swellings extend over the cheeks 

 and face, closing the eyes, or in some cases, if the retrobulbar 

 tissue becomes involved, may force the eyeballs from their 

 sockets. The swellings may become very tense and drops of 

 serum ooze from them. In some cases the lips, cheeks, and 

 tongue are so swollen that it is impossible for the animal to 

 eat or drink. Dyspnea is a common symptom. The tem- 

 perature ranges from 104° to 107° F. The skin often sloughs 

 over the swollen areas, and the wool over the entire body may 

 be shed. Fregnant ewes frequently abort. Sheep which 

 recover are usually left permanently unthrifty. 



Treatment. — Internal treatment (belladonna, turpentine, 

 strychnin, arsenic, digitalis) has been found useless. • On the 

 other hand, smearing the head of the affected sheep with 

 vaselin or olive oil, especially if the sheep are permitted to 

 rest in the shade, has been of service. Scarifying the swell- 

 ings does no good, and exposes the parts to further infection. 



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