LOCOWEED DISEASE OF SHEEP 379 



"loco disease" is seen during moist seasons, othei's that a dry season favors 

 the spread of the disease by decreasing the amount of the nutritious grasses. 



Sy7nptoms and course of the disease. The onset is described as being 

 usually gradual and insidious, several weeks after the animal first eats 

 the weed. A rapid onset is described at times, and occasionally symptoms 

 appear within a week after exposure. In Eastern Colorado it seems not un- 

 usual for a horse to become "locoed" a day or two after beginning to eat 

 the weed. The sjonptoms are more definite in the horse. A previously well 

 broken horse becomes unmanageable, bucking, rearing and exhibiting vari- 

 ous vicious traits, together with a high degree of nervousness. The animal 

 appears to suffer from defective vision and even from hallucinations. It 

 is subject to tremors of excitement. Most characteristic appears to be 

 the tendency of "locoed" horses to balk at objects in front of them. Thus 

 they will balk at a stick or a rope lying in their path, and if forced to cross 

 it, they will clear it with a leap several feet in the air. It is said that a "lo- 

 coed" horse cannot be led nor ridden, though it may at times be driven, 

 but that when once started the horse will not stop before it is exhausted. 

 The nervous symptoms continue. Very soon the animal begins to lose 

 strength and weight; emaciation finally becomes extreme, the coat is 

 rough and dull, the ears and head droop, the gait becomes weak and un- 

 steady, the .eyes sunken and glassy, and the animal very apathetic. Oc- 

 casionally one side or one limb may be weaker than the rest of the animal. 

 Stiffness of the hind legs is especially common. Schwartzkopf states that 

 the pupils are widely dilated and that there is a decrease of sensibility to 

 mechanical stimulation. Apparently the animal is in almost a constant 

 state of nervous tremor. The disease is usually chronic, lasting from several 

 months up to two or three years. The horse spends its time searching for the 

 locoweed, which it may even dig up by the roots with its hoof. In the last 

 stages the horse may walk bhndly into a tree or rock and stand pushing 

 against it until it drops from exhaustion, or it may fall in the water from 

 which it is drinking and drown. In the chronic disease, horses occasionally 

 exhibit acute maniacal attacks from which they may die suddenly with 

 evidences of great pain. Acute attaclcs, can be brought on by exciting the 

 animal or by making it exercise until it is hot. 



Locoweed disease of sheep and cattle is less fully described. The chief 

 symptoms are the habit of eating the locoweed, nervousness, loss of weight 

 and strength ending in great emaciation, with dull glassy eyes, rough coat, 

 and finally death from exhaustion. Stiffness of the muscles of the neck and 

 hind legs is regarded as quite characteristic in sheep. 



Morbid anatomy. No characteristic lesion has been found except the 



