Cowan strongly condemns heavy smearing with tar, which he believes to encrease the mortality, by lowering the general tone of the system: “Hoggs are very dull and listless for some time after being smeared with tar, more especially if heavily smeared; ... when the skin is taken off, every shed or opening in the wool where the tar has been laid on, is as distinctly visible upon the flesh as the stripes upon a piece of printed calico.”
It has been further alleged that the deaths are especially common during the full of the moon, the usual explanation being that the sheep are tempted to feed in the night and overload the stomach. It may be added that at such times the grass is taken in a cold—(often frosted) condition so as to chill the stomach and cause a congestive reaction, and that short of this, under the night dews the microbian ferments are moist and ready to start into full activity, while the herbage if it has been partly frosted is particularly susceptible to bacteridian attack.
Bacteriology of Braxy. The essential cause of braxy was revealed by Ivar Nielson in 1888, who demonstrated on the local lesions of the alimentary canal and the capillaries of various internal organs a bacillus which he named bacillus gastromycosis ovis. This is 2 to 6μ long by 1μ broad, occurring in pairs or filaments. The organism has an elliptical form and stains deeply at the extremities, while the central, bulging portion fails to take the color, is highly refrangent, and represents the spore. The non-spore-bearing bacilli are long, uniform rods with rounded ends. The germ is anærobic, grows readily in serum glycerine agar, and is gas producing and foul smelling. Liquefies gelatine. It is found abundantly in the congested parts of the abomasum and to a less extent in the bowels, in the mucosa, and in the submucous and subserous tissues. It was also found in the blood and in the small areas of degeneration in the liver and kidneys. Jensen obtained pure cultures through the survival of the spores when impure cultures were boiled for a few minutes.
Animals Susceptible. Inoculation of the cultures subcutem produces an affection resembling malignant œdema, or braxy, in sheep, Guinea pigs, mice, pigeons and hens, and less certainly in rabbits. Inoculation of a calf had no deleterious effect, while a second succumbed in forty-eight hours. In its pathogenesis this microbe appears to be more closely allied to that of malignant œdema than that of black quarter, as the latter attacks cattle very readily and has little effect on rabbits, pigeons and chickens.
Symptoms. The more obvious manifestations of braxy bear a resemblance to those of black quarter, so that the two affections have been often confounded. In both the attack is sudden, the course rapid and fatal, the back arched, the step short, especially with the hind limbs, and there are swellings which crepitate on pressure on the hind quarters or some other part of the body. Symptoms of colic soon appear, the sheep lying down and rising frequently and moving the hind limbs uneasily, and the abdomen becomes distended, tympanitic and tender. Rumination and feeding are promptly suspended, and as a rule defecation as well. Urine may be passed frequently in small amounts and of a high color. The pulse is rapid and often irregular and the breathing hurried and labored. In some cases the abdominal pain is less acute, the animal standing apart with drooping head, ears and eyelids and frothy lips, or lying by itself at a distance from the flock. Sooner or later emphysematous swellings appear on some part of the body, but most commonly on the hind quarter, which have a soft, doughy feeling and crackle or gurgle on pressure. In the great majority of cases, however, the disease runs a rapid course and ends in death in a few hours, and as the attacks are mostly in the cold of the night, the victim, which appeared well at night, is found dead in the morning. Cowan has often noticed that those that stepped short at night were dead next morning. In certain cases the sheep stood obstinately to the end and fell dead as if shot. When death was deferred for several days a common result was shedding of the wool.
Pathological Anatomy. A marked feature of braxy is the early putrefaction of the carcass. The rigor mortis quickly passes and the carcass bloats up and exhales a putrid odor. On removing the skin one sees extensive sero-sanguineous exudations, mixed with bubbles of gas of an offensive odor. The abdomen is tense and tympanitic and the anus protrudes. Visceral lesions are especially marked in the fourth stomach, the walls of which are thickened in patches or throughout by a hæmorrhagic or sero-hæmorrhagic exudation of a dark purplish color. If killed in the early stages this may be very restricted in area, but becomes general in animals that have died of the disease. Similar exudations are found on the walls of the first three stomachs, or on the small or large intestines. The fourth stomach and duodenum are, as a rule, empty of food, though containing a sanguineous liquid. The contents of the large intestines are usually dry and hard. Some serous exudate is usually present in the peritoneum, pleura and pericardium. The spleen may be normal or slightly enlarged. The liver is pale, soft and friable. The kidneys may be congested and swollen and usually show brownish areas of necrosis in which the bacillus is readily found. The blood is dark, and though it may be coagulated, the clot is usually soft and diffluent.
Prevention. Much may be done in the way of drainage and above all cultivation and liming of the braxy pastures, and again laying them down in grass. Cowan found that braxy diminished largely in ratio with the improvement and cultivation of the soil. A rotation of crops and the free æration of the soil tends to destroy an anærobic microbe or to render it non-virulent. Winter feeding is another well attested source of protection. Hay with turnips, oats, linseed cake or oil cake seems to encrease the tone and vigor, and to counteract the fermentations in the digestive organs which lay the system open to attack. Wholesome and nutritious food then must be a main stay whenever the health threatens to be undermined by insufficient or unwholesome pasture, by dried or withered grass, ferns or heather, by the watery grass of recent and rapid growth, by frosted and partially decayed herbage, or by pasture exhausted by overstocking or drought.
Fields and hills known to be infecting must be abandoned especially in late fall and winter and in the case of the younger and more susceptible sheep. Understocking is always better than overstocking as the flock is kept better nourished, stronger and with a greater measure of tolerance and resistance. Upon land covered with old, fibrous, astringent heather, burning is often of great value. The new growth of young heather is much more digestible and nutritious, and destitute of injurious astringency, and maintains a stronger and healthier flock.
Finally the question of immunization arises. Nielsen attempted this by drying and heating to sterilization the diseased kidney and injected small quantities of this suspended in water. Sheep treated in this way in Norway and Iceland have had a circumscribed inflammatory swelling and afterward appeared to resist casual infection when placed on the braxy fields. Jensen carried the experiment a step farther and inoculated his artificially immunized sheep with 2½ cc. of a virulent serum-gelatine-agar culture. It was rather unwell for half a day and walked lame but soon recovered. A dose of ¹⁄₃₀ cc. of the same culture killed in fifteen hours a larger sheep that had not been artificially immunized.
Treatment. Though some cases of braxy recover yet the treatment of the disease can hardly be seriously considered as yet. A disorder which is so rapid in its progress, so early associated with such great and rapidly extending lesions of the most vital organs, and which proves fatal so early and almost invariably, leaves little room for a successful treatment. In the milder cases, likely to recover of their own accord, this may be hastened by the internal use of antiseptics and purgatives, and perhaps even by antitoxic serum from the blood of an immunized animal.