Part 5

=CLINICAL SYMPTOMS OF LOCOED ANIMALS AS DESCRIBED IN LITERATURE.=

The animals usually affected are sheep, horses, cattle, mules, donkeys, and goats. It is claimed that practically all herbivorous animals are liable to the disease, even antelopes being affected. Hogs are said to be unaffected, but definite information is lacking. Cows seem to be less sensitive to this form of intoxication. The condition is usually a chronic one, although acute cases are said to occur at times. The symptoms consist of digestive disturbances, associated with emaciation and various symptoms suggesting lesions in the nervous system, central or peripheral. The animals lose their appetite from the first, begin to emaciate, and show symptoms of malnutrition and starvation. The head trembles, the gait becomes feeble and uncertain, the eyes become sunken and have a "flat, glassy look." There is a general sluggishness, muscular incoordination, and difficulty in motion; finally all control of the limbs is lost and the animal is unable to stand; the coat becomes rough and loses its luster, and, in fact, all the typical symptoms of starvation appear. In some cases diarrhea is also present.

All of Nockolds's animals, however, were constipated and the stools were covered with mucus. The dependent portions of the body may swell, simply as an expression of the anæmia. Sometimes there are symptoms indicating acute pain, the animals running about as if affected with colic. They may belch and their abdomens swell. Some claim that the animals are markedly salivated so that the saliva trickles from their mouths. In other cases the mouth may be dry. The eyes may be rolled up so that the whites alone show. In some cases the pupil has been noted to be dilated, as in atropine poisoning, but Wilcox states that they are contracted as after the use of eserine. The temperature of the animal falls from 1/2 degree to 1-1/2 degrees F. below normal. Tetanic symptoms may occur, or the muscles of the mouth and tongue becoming paralyzed may interfere with mastication. When water is offered to the animal, it gazes stupidly at it and may not drink for days. One of the symptoms noted is the loss of power to back properly. Cows during the first two or three months of gestation are almost sure to abort. This is claimed by Knowles, however, to be due to malnutrition. As a result of these observations, suggesting some uterine action, the drug has been proposed as an emmenagogue.

The psychical symptoms are shown by errors of judgment. The animal becomes dull and spiritless and wanders about half dazed. The mental dullness passes into stupor. This dull, stupid condition has been compared to intoxication with opium. If the locoed horse is led across a stick lying on the ground he often jumps high as if it were a great obstacle. The animal may now have maniacal attacks, during which he rears and may fall backward, and makes unreasonable jumps and other unexpected movements, thus rendering himself dangerous to man. Other symptoms due to disturbances of the central nervous system are hallucinations of various sorts. Though the optic nerve itself is apparently not affected, the animal will stare at an object for a long time without any apparent comprehension of its nature. This disturbance in the visual function McCullaugh claims to be one of the first symptoms of this disease. The animal seems to lose all idea of distance, as he will butt against an obstruction as if oblivious of its presence. Any sudden or violent motion made before him may cause him to fall. According to some, the animal loses the sense which guides him in finding water. A cow may fail to recognize her calf. There is more or less loss of control of the limbs and tremors; the feet are lifted abnormally high when trotting, and, if crowded, the animal falls headlong and will jump over little hollows as if they were wide ditches. The horse may shy without apparent cause and kick at imaginary objects, and, in fact, the reasoning powers seem to be lost. These attacks are brought on by sudden excitement or when crossing water. There may be cutaneous hyperæsthesia.

The animals may remain with the herd, but they often wander away. Stalker records the following observations:

I have seen a single animal miles away from any other individual of the herd, carefully searching as if for some lost object, and when a loco plant is found he would devour every morsel of it with the greatest relish. As soon as one plant was eaten he would immediately go in search of more, apparently oblivious to everything but the intoxication afforded by his one favorite article of food.

All of Nockolds's animals which were locoed were mares more than 6 years of age.

According to Stalker there is a passive type in which the animal shows symptoms only on being disturbed; the animal then becomes unmanageable. This happens even with old, well-broken saddle horses.

There are few published reports as to the symptoms occurring in sheep which are locoed. Stalker says sheep "become loco-eaters, grow stupid, emaciated, and eventually die." One of the few descriptions of the symptoms is that of Ruedi, in which he claims that the symptoms in sheep are those comparable to the symptoms of cerebro-spinal meningitis except that there is an absence of fever. Ruedi speaks of sheep "lying flat on the ground, not able to stand, and not able even to lift their heads to drink the offered water; the head and the vertebra in opisthotonus position; the four legs stretched out and stiff; breathing was stertorous, pulse slow, abdomen much distended, diarrhea present. * * * The heart * * * was very slow and insufficient." The teeth (in sheep) may blacken and fall out.

It is mainly the young animals, such as lambs and colts, that are affected, probably due to the fact that their attention is more easily directed to the flower of the loco plants. It is claimed (on slight evidence) that men have become locoed. The symptoms in them are nausea and headache.

Schuchardt has called attention to the resemblance of the symptoms in locoed animals to those which occur in so-called lathyrism, but most observers in this country have especially marked the resemblance of the symptoms to those induced by the habitual use of narcotic drugs.

As a rule the loco plants are refused by animals save when there is lack of other food, although at times animals have shown the keenest relish for these plants, rejected all other forage, and devoted their whole attention to searching for the loco plants.

Stalker says that animals not too long addicted to the use of these plants, if confined, soon lose their taste for them (after two or three months), although old loco eaters do not readily lose the habit. Stalker also says that "it is to be presumed that the plant is possessed of some toxic property that has a specific effect on the nervous centers, and that these effects have a marked tendency to remain permanent."

The fundamental character of the disorder seems to be a progressing anæmia. The interpretation of psychical symptoms in herbivora, and especially on the range, must often be fallacious.

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FOOTNOTES:

Kingsley, B. F. The Loco Plant. Daniel's Texas Medical Journal, vol. 3, p. 522. 1888.

Schwartzkopff, O. The Effects of "Loco-Weed." Amer. Vet. Rev., vol. 12, p. 162. 1888.

McCullaugh, F. A. Locoed Horses. Journ. Comp. Med. & Vet. Archives, vol. 13, p. 435. 1892.

Eastwood, A. The Loco Weeds. Zoe, vol. 3, p. 57. 1892.

Vasey, G. Plants Poisonous to Cattle in California. Report of Commissioner of Agriculture for 1874, p. 159. 1875.

Vasey, G., l. c., p. 159.

Nockolds, C. Poisoning by Loco Weed. Amer. Vet. Rev., vol. 20, p. 570. 1896-7.

Patterson, A. H. Starvation OEdema. Med. Rev., vol. 56, p. 715, 1899.

Vasey, G. Botanical Notes, Monthly Reports of Dept. Agriculture for 1873, p. 504. 1874.

Anderson, F. W. Poisonous Plants and the Symptoms They Produce. Bot. Gaz., vol. 14, p. 180. 1889.

Schwartzkopff, O. The Effects of "Loco-Weed." Amer. Vet. Rev., vol. 12, p. 161. 1888.

Wilcox, T. E. Treatment of "Loco" Poisoning in Idaho Territory. Med. Rec., vol. 31, p. 268. 1887.