LOCO POISONING. OXYTROPIS LAMBERTI. ASTRAGALUS MOLLISSIMUS
Astragalus Hornii: A. Lentiginosus: A. Mollissimus: Oxytropis Lamberti: O. Multifloris: O. Deflexa: Sophora Serecia: Malvastrum Coccinium: Corydalis Aurea. In dry regions. Cause, a psychosis. Emaciation. Lassitude. Impaired sight. Illusions. Vice. Refuses other food. Contradictory views. Experiments by Dr. Day.
The term loco is of Spanish origin and has come to us through the Spanish speaking residents on the cattle raising plains and the Pacific Coast. The word is defined to mean mad, crazy, foolish. It has been applied indiscriminately to a disease in stock manifested by these symptoms, and to a variety of leguminous plants, found growing on the western lands and supposed to cause the disease in question. The plants complained of are Astragalus Hornii, and A. Lentiginosus (Griesbach) in California, A. Mollissimus (Torrey) and Oxytropis Lamberti (Purshiana) in Colorado and New Mexico. Other allied species, and like these found also in the other Rocky Mountain States, Sophora Serecia, Oxytropis Multifloris, O. Deflexa, Malvastrum Coccinium, and Corydalis Aurea var. Occidentalis have been less confidently charged with producing the disease.
These plants grow on poor, dry, sandy or gravelly soils, and having great power of resisting drought, are often in fair growth, and present an abundant mass of leaves when surrounding vegetation is withered up. Hence, it is alleged, the animals are driven to use it when nothing else is obtainable and once accustomed to it, the desire for more becomes a veritable craze or neurosis, and the victim searches for it and devours it to the exclusion of other food.
The following quotations may serve to illustrate the effects alleged:
Among the symptoms first noticed are loss of flesh, general lassitude and impaired vision; later the animal’s brain seems to be affected; it becomes vicious and unmanageable and rapidly loses both flesh and strength. Frequently when approaching some small object it will leap into the air as if to clear a fence. The patient also totters on its limbs and appears as if crazy. After becoming affected it may linger many months, or a year, but usually dies at last from the effects of the complaint. (Dr. Vasey. Report of Dept. of Agriculture, 1884).
“I think very few if any animals eat the loco at first from choice; but as it resists the drought until other food is scarce they are first starved to it, and after eating it a short time appear to prefer it to anything else. Cows are poisoned by it as well as horses, but it takes more of it to affect them. It is also said to poison sheep. As I have seen its actions on the horse, the first symptom apparently is hallucination. When led or ridden up to some little obstruction, such as a bar or rail lying in the road, he stops short, and if urged, leaps as though it were four feet high. Next he is seized with fits of mania in which he is quite uncontrollable and sometimes dangerous. He rears, sometimes even falling backwards, runs or gives several successive leaps forward, and generally falls. His eyes are rolled upward until only the white can be seen, which is strongly injected and as he sees nothing, is as apt to leap against a wall or a man, as in any other direction. Anything which excites him appears to induce the fits, which, I think, are more apt to occur in crossing water than elsewhere, and the animal sometimes falls so exhausted as to drown in water not over two feet deep. He loses flesh from the first and sometimes presents the appearance of a walking skeleton. In the next and last stage he only goes from the loco to water and back, his gait is feeble and uncertain, his eyes are sunken and have a flat, glassy look, and his coat is rough and lustreless. In general the animal appears to perish from starvation and consequent excitement of the nervous system, but sometimes appears to suffer acute pain, causing him to expend his strength in running wildly from place to place, pausing and rolling, until he falls and dies in a few minutes.” (O. B. Ormsby, Report Dept. of Agriculture, 1874.)
“Animals are not fond of it at first, or don’t seem to be, but after they get accustomed to the taste they are crazy for it and will eat little or nothing else when loco can be had. There seems to be little or no nutrition in it as the animal invariably loses flesh and spirit. Even after eating of it they may live for years, if kept entirely out of its reach, but if not, they almost invariably eat of it until they die.” (Mrs. T. S. Whipple, San Luis, Cal. Report Dept. of Agriculture, 1874).
“Cattle, after having eaten it,” Oxytropis Lamberti, “may linger many months, or for a year or two, but invariably die at last from the effects of it. The animal does not lose flesh apparently, but totters on its limbs and becomes crazy. The sight becomes affected so that the animal has no knowledge of distance, but will make an effort to step over a stream or an obstacle while at a distance off, yet will plunge into it or walk up against it on arriving at it.” (Dr. Moffat, U. S. Army.)
“The term loco, simply meaning foolish, is applied because of the peculiar form of dementia induced in the animals that are in the habit of eating the plant. Whether the animals (horses chiefly) begin to eat the plant from necessity (which is not likely) or from choice, I am unable to say. Certain it is, however, that when once commenced, they continue it, passing through a temporary intoxication, to a complete nervous and muscular wreck in the latter stages, when it has developed into a fully marked disease, which terminates in death from starvation or inability to digest more nourishing food. The animal, toward the last, becomes stupid or wild, or even vicious, or again acting as though attacked with blind staggers.” (Dr. Rothrock, Report of Dept. of Agriculture, 1884).
Dr. Isaac Ott, of Easton, Pa., gives the following as the physiological action of the Astragalus Mollissimus: “It decreases the irritability of the motor nerve, greatly affects the sensory ganglia of the central nervous system, preventing them from readily receiving impressions. Has a spinal tetanic action. It kills mainly by arrest of the heart. Increases the callory secretion. Has a stupifying action on the brain. Reduces the cardiac force and frequency. Temporarily increases arterial tension, but finally decreases it. Greatly dilates the pupil.” (Amer. Jour. of Pharmacy, 1882).
In opposition to these statements Professor Sayre, of Kansas, after an extended observation, arrived at the conclusion that “it is a grave question whether loco weed is a poison at all; upon chemical examination no poisonous principle of any kind was discovered; no toxic effect was observable when administered to frogs, cats, dogs, or the human species, ... the point cannot be accepted as a settled one whether loco is poisonous to cattle or not.”
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.
“From the close agreement of the symptoms in the cats with those universally recognized in locoed horses and cattle, I conclude that the cases described above were genuine cases of the “loco disease” and are, so far as can be ascertained, the first that were ever experimentally produced.”
“The craving for the “loco” is soon acquired. The kittens would beg for it as an ordinary kitten does for milk, and when supplied would lie down contented. To determine whether a herbivorous animal would easily acquire the “loco habit” a young “jack” rabbit was captured and fed a few days on milk and grass; then fresh “loco” was substituted for the grass. At first the “loco” was refused, but soon it was taken with as much relish as the grass had been. After ten days of the milk and “loco” diet the rabbit was found dead, with the head drawn back and the stomach ruptured.”
“With reference to the character of the plants at the different seasons of the year, I am convinced by numerous experiments, on material gathered in different months, that the greatest amount of poison is present in the autumn and winter.” The scarcity of other food at that period of the year is only a partial explanation of the number of deaths occurring at that season.
Conclusions:
“1st. There is some poison in “loco weed” which may cause the illness and, if sufficient quantity is taken, the death of an animal.”
“2d. This poison is contained in the decoction obtained from the plants, and by systematically feeding it to healthy cats cases of “loco” disease may be produced.”
“3d. Taste for the green “loco weed” may be experimentally produced in the jack rabbit.”
“4th. From the large quantity of the plant or the decoction required to produce the disease, the poison must be weak, or if strong, it must be in very small amount.”