1st. Enforced inactivity. In every instance that has come under my notice the ewes have been confined for several months to a barn or at most a confined yard so that exercise became impossible. The muscular system was flabby and soft, although as a rule there was abundance of fat, and the number of red globules did not vary much from the normal. In an animal that is naturally so active, and so accustomed to outdoor life the reduction of tone and vigor is to be expected. The same evil shows in other directions, thus after a snowy winter and close confinement the crop of lambs will sometimes perish of goitre without exception, while in subsequent years, with enforced exercise of the ewes, practically all escape.
2d. Twin lambs have been found in the womb of almost every case examined. The extra drain upon the system, and the depressing action of the load on an atonic ewe together with the symptomatic irritation are to be noted.
3d. The near approach of the completion of gestation, the cumulative effect of a long pregnancy, and perhaps the absorption of metabolic products from the fœtal membranes in course of preparation for detachment, and of leucomaines from the physiologically active or developing mammæ, doubtless have a prostrating influence on the susceptible nervous system.
4th. All had been fed on clover hay either as an exclusive diet or as part of their ration. This is sufficiently nutritive, as testified by the fat condition of the patients, but it may be that it was too nitrogenous for such an inactive life. Again the clover hay usually abounds in cryptogams and bacteria and their products, which may have contributed somewhat to the asthenia.
5th. Concurrent diseases, in individual cases or flocks, manifestly contributed to the general loss of nervous power. In some the bowels were studded with the nodules of the œsophagostoma, in others œstrus larvæ had extensively invaded the nasal sinuses, one had congestion of the mucosa of the small intestines, some had congestion and fatty degeneration of the liver, others had fatty kidneys, and one had a papilloma pressing on the spinal cord. Manifestly diseases and degenerations of various kinds would still further undermine nervous energy and add to the atony.
Cold and heat did not seem to dominate, as most were kept in warm barns, and wore heavy winter fleeces, while one clipped early in December, and kept in an atmosphere of 40° to 55°, was attacked in the second week of January.
As this experience was had in a goitre district it may become a question whether the poison of this disease was a causative factor. Goitre was not a prominent feature in either ewes or lambs.
Symptoms. Variable. The most prominent are, leaving the flock, moping alone, grinding the teeth, drooping and trembling of head and ears, temperature normal or subnormal (100.5°), respiration 24, pulse 80, feeds and ruminates sparingly, bowels normal, buccal mucosa pale, conjunctiva hyperæmic, in some cases stupor and partial blindness, the animal walking against racks or fences, walk is slow and unsteady, the muscles feel soft and flabby, the abdomen may be full, but its walls are quite flaccid so that the lambs can be easily felt. As the disease advances all symptoms are aggravated, food is no longer taken, rumination ceases, the ewe remains recumbent, cannot be made to rise, and when lifted and carried makes no struggle. After 24 hours of this helpless condition death supervenes. In some instances labor pains have come on and the ewe has perished in a vain effort at delivery. Illness lasted about a week.
Prominent lesions have been noted under causes. It need only be added that no notable difference from the normal was found in making a count of the red globules, and the size of the individual globule was normal or only perceptibly smaller as is to be expected in a dense plasma. In different cases there was found congestion of the abomasum, small intestine, liver and brain.
Prevention. The most important measure is to maintain a strong, well-developed muscular system, and a vigorous nervous tone by a sufficiency of out door exercise during the winter months. Half a mile or a mile at least should be given daily to the breeding ewes, no matter what the attendant difficulties. If clover hay is musty it should be replaced in whole or in part by another kind. Parasites and other diseases which tend to lower the general tone should be appropriately treated.