198 RURAL VETERINARY SECRETS 



BIGHEAD 



Bighead is characterized by a sudden swelling of the head and 

 ears. The affection is not \ery widely distributed. It is found in Utah 

 and the surrounding States, and greatest losses occurring in southern 

 and central Utah, southern Idaho, eastern Nevada, and western and 

 southern Wyoming. It is also seen occasionally in sheep brought as 

 feeders from those regions into the Middle Western States. In such 

 cases the disease occurs shortly after the arrival of the animal early 

 in the autumn if the heat is excessive. 



CAUSE 



The definite cause of bighead is not known, though climatic con- 

 ditions have much to do with its appearance. Sheep are usually af- 

 fected during the early spring and early summer while being driven 

 from the winter to the summer ranges, more commonly before shear- 

 ing. Bighead appears to be most prevalent after a cold or stormy 

 night, when the day following turns hot and the animals are driven 

 fast in the hot sun, and when they are compelled to inhale a consider- 

 able quantity of alkali dust. It affects males and females alike, though 

 it is seldom seen in young lambs. This condition affects sheep in much 

 the same way as man is aff'ected by poison ivy. The disease is not 

 transmissible from one sheep to another or to other animals. All ex- 

 periments with transfusion of blood or injection of serum from affect- 

 ed sheep to healthy ones were without results. 



The disease of sheep in luirope, known as fagopyrism or buck- 

 wheat poisoning, is similar to bighead. In one experiment in America 

 bighead was produced by feeding buckwheat and exposing the animals 

 to the sun. In another experiment the results were negative. On the 

 desert and on different parts of the trail sheep eat a number of plants 

 that belong to the buckwheat family, and it is possible that the trouble 

 mav come from that scource. 



SYMPTOMS 



The first noticeable symptom is that the animal begins to tlirow 

 it> head up and sidewise in a jerking manner. It is greatly irritated 

 and shakes the head and tries to rub it. The animal walks aimlessly- 

 through the flock, often stamping its feet on the ground, and seldom 

 standing still very long. The eyesight is affected, as the animal fol- 

 lows n direct line, sometimes runninij into other sheep and other oh- 



