562 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



to eating white loco weed. Close observation, however, will readily 

 distinguish one from the other. Locoed sheep show symptoms of poi- 

 soning, while giddy sheep show evidences of brain trouble or more 

 rarely of trouble in the spinal cord. Locoed sheep are nervous, un- 

 certain in their movements, and out of condition, but they never 

 show the regular automatic repetition of some unusual movement 

 that giddy sheep show. Giddy sheep very commonly turn in a circle, 

 a very characteristic symptom. The circle may be relatively large or 

 very small, or the sheep may even pivot in one place. A giddy sheep 

 will sometimes graze for awhile, then raise its head as if it had just 

 thought of something and start off for it, swinging around in a circle 

 and perhaps stopping and beginning to feed in the place from which 

 it started. Later, the sheep will circle for hours without stopping. 

 Less often the sheep will throw the head back and bolt in a straight 

 line as if frightened, or perhaps put the head between the front legs 

 and go stumbling forward. The head is often held to one side and 

 may be raised or lowered. 



On the range the first symptom that the herder notices is that 

 giddy sheep become hard to herd. They lag behind the flock, and 

 when the dog is sent to bring them up, instead of running into the 

 flock as normal sheep would, they run away from it. When the rest 

 of the flock is standing quiet, giddy sheep can be seen worming rest- 

 lessly about in it ; and wnile the others are feeding, giddy sheep will 

 be executing some meaningless maneuver, such as circling or running 

 without any apparent cause. 



Locoed sheep when put on alfalfa will nearly always recover; 

 giddy sheep will show no abatement of symptoms and will invariably 

 die unless operated on. When a sheepman has any doubt as to 

 whether his sheep have gid or some disease which merely resembles 

 gid, it will pay to kill a sheep and examine the brain. The devel- 

 oped gid parasite is large and easily recognizable as a bag full of 

 fluid, and its presence is proof that the sheep had gid. It is of course 

 perfectly possible for a sheep to have loco disease and gid simulta- 

 neously, tnough no cases of this sort are known, so far as available 

 records show. 



COMPAEISON WITH SYMPTOMS OF GRUB IN THE HEAD. 



Sheep which are infected with so-called grub in the head (the 

 larva of CEstrus ovis, the sheep gadfly) may sometimes be suspected 

 of having gid. However, such sheep are characterized by a catarrh 

 or "snotty nose," due to the irritation caused by the parasite in the 

 nose and frontal sinuses. They do not show the automatic move- 

 ments of giddy sheep. Grub in the head is rarely fatal, though sheep 

 may die from a massive infection or from the larva or grub pene- 

 trating to the brain, a thing which it is claimed may happen in rare 

 cases. The disease may be definitely diagnosed by a post-mortem 

 examination of the back part of the nose and frontal sinuses, where 

 grubs will be found if the disease is grub in the head. This disease 

 is especially common in Sweet Grass County. Gid and grub in the 

 head sometimes occur in the same sheep, at the same time, and a 



