Dr. G. C. Faville found in locoed sheep in Colorado bunches of tapeworms in the gall ducts. Dr. Cooper Curtice, who subsequently studied the subject, found the tænia fimbriata, and believes that to these the symptoms are exclusively due. “The affected lambs are large headed with undersized bodies and hidebound skins. Their gait is slightly like that of a rheumatic. They seem to have difficulty in cropping the shorter grass; they also appear to be more foolish than the other sheep, standing oftener to stamp at the sheep dogs or the herder than the healthier ones. Others do not seem to see as well, or are so affected that they seem to appreciate danger less. In driving, they are to be found at the rear of the flock.” (Animal Parasites of Sheep.)
It is altogether probable that the tæniasis of sheep has been mistaken for loco, but this can hardly account for the remarkable symptoms found in other genera of animals, as a concomitant of an acquired and insatiable fondness for these leguminous plants. The tænia fimbriata has been found in sheep and deer, but there is no record of it as a parasite of cattle and horses.
Dr. Sayre’s failure to find any poisonous principle in the plants, or any toxic action on frogs, dogs or cats, cannot be received as conclusive in face of the results reached by others. Perhaps Dr. Sayre’s specimens were not grown under the proper conditions, or were not collected in the proper season to secure the toxic ingredient.
Miss C. M. Watson, of Ann Arbor, Mich., succeeded in separating a small amount of alkaloid from the root of Oxytropis Lamberti, but did not apply the crucial test of physiological experiment. In the Report of the Department of Agriculture for 1879, are given analyses of Oxytropis Lamberti, Astragalus Mollissimus and Sophora Speciosa, in each of which a small amount of alkaloid was found.
In 1888–9, Dr. Mary Gage Day, of Wichita, Kansas, made careful experiments on cats and rabbits, under the supervision of Dr. Vaughan in the Michigan Laboratory of Hygiene. She used a decoction of roots, stems and leaves of plants gathered in September and gave 60 to 70 c.c. of this to a half-grown vigorous kitten daily, along with abundance of milk and other food. In two days the kitten became less active, showed rough coat, increased desire for the loco, with partial loss of appetite for other food, diarrhœa came on, and retching and vomiting occasionally occurred. The expression became peculiar and characteristic. These symptoms increased, and emaciation advanced, and on the 18th day periods of convulsive excitement supervened. These were sometimes tetanic, the head being thrown backward and the mouth frothing. At other times the kitten stood on its hind limbs and struck the air with its fore paws, then fell backward and threw itself from side to side. There were short intervals of quiet, life being indicated by breathing only. After 36 hours of these intermittent convulsions paraplegia set in, and the kitten died in two hours. There was no apparent loss of consciousness before death.
Post mortem examination revealed gastric and duodenal ulcers, some of which were nearly perforating. The heart was in diastole; brain and myel appeared normal; the entire body anæmic.
To a vigorous adult cat 60 c.c. to 70 c.c. of a more concentrated solution were given with other food. The results were essentially the same. By the twelfth day the cat was wasted to a skeleton and very weak. Paralysis of the hind limbs came on and the cat died on the thirteenth day.
As a test experiment, two strong young cats were confined in the same place, fed from the same dish, and treated in every way the same, except that the one was fed daily a decoction of the loco. The one fed loco acquired the loco disease with the symptoms described above while the other, eating ordinary food only, remained healthy.
Subcutaneous injections of the concentrated decoction thrown into frogs and chickens at the Michigan Laboratory of Hygiene, under direction of Dr. Victor C. Vaughan, caused nervous twitching and in large doses, death in 1 or 2 hours from heart paralysis. The same symptoms were produced in frogs by injection of an alcoholic extract of the residue left after evaporation to dryness of the decoction.
The loss of appetite, acquired liking for the “loco weed”, rough coat, emaciation, peculiar expression, rearing, plunging, and a staggering uncertain gait are among the symptoms given in the earliest published observations on the loco disease, and agree with the statements universally made by ranchmen. An ulcerated condition of the intestines was also pointed out by Professor Sayre in a locoed cow upon which he made a necropsy (Dodge City Times, July, 1887): but the diarrhœa which was so marked a symptom in the cats experimented on, is not mentioned as a characteristic symptom in horses and cattle.