DISEASES OF SHEEP 561 



side of this period. The adult worms develop in dogs, and probably 

 in coyotes and other wolves also, from eating the heads of sheep 

 dying of gid during the months mentioned. These worms require a 

 month or two to develop to the point where the tapeworm eggs are 

 passed with the feces, and eggs from dogs infected at this time are 

 probably being spread over the pasture and range any time after the 

 1st of February. Up to the time of the spring rains it is unlikely 

 that many sheep become infected. It is likely that up to the time of 

 the rains the eggs generally lie alive and untouched or else perish. 

 It is only as the feces are promptly broken up by water and the eggs 

 released that sheep are liable to become infected. From the time 

 the spring rains set in usually during May, it is said the sheep, 

 now on summer range, take up the infection. The beating rain 

 breaks up the dog feces, washes the tapeworm eggs into puddles and 

 reservoirs from which the sheep drink, and splashes them on the 

 grass which the sheep eat. Allowing the usual nine months' period 

 of development, sheep infected in May will die in December. The 

 deaths from January to March, inclusive, indicate that the storms of 

 June, July, and August play a part in the infection of sheep. From 

 this time dry weather apparently saves the sheep from further infec- 

 tion on the summer range, and on removal to winter range cold 

 weather probably serves to keep the feces frozen, and thereby pre- 

 vents them from breaking up and washing about. The death at this 

 time of sheep infected the previous spring and summer gives oppor- 

 tunity for renewed infection of dogs and probably of other carnivora. 

 Thus the life cycle takes about a year for its completion, and is 

 closely related to weather conditions. 



It appears from a study of field conditions that gid is most prev- 

 alent in the winters following a spring when the rainfall is abundant, 

 an opinion expressed by many European writers, and in places where 

 the range is most thoroughly carpeted with forage. In parts of the 

 plains country of southeastern Montana where the forage is largely 

 bunch grass, the range has not yet become infected, in spite of giddy 

 sheep brought in from the infected region. The infection seems to 

 persist better in upland valleys. In some of these infected localities 

 the ground is covered with a moss in the spring, and it is said that 

 the sheep are very fond of this. It seems evident that the washing 

 about of feces deposited on such a moss carpet or on a range where 

 the grass grows in a continuous mat would be more certain to leave 

 tapeworm eggs where sheep would get them than feces deposited on 

 the bare ground in a country where they could wash along on the 

 ground between scattered bunches of grass. The necessity of water- 

 ing sheep on summer ranges at shallow watering places and in reser- 

 voirs and ponds in coulees where contamination by dogs is inevitable 

 must also play some part in the infection of sheep. 



SYMPTOMS OF GID. 



COMPARISON WITH SYMPTOMS OF LOCO POISONING. 



In a general way the symptoms of gid in sheep are such that the 

 sheepmen may be pardoned for confusing gid with loco disease, due 



