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.”