Animal anatomy, histology, pathological anatomy

4. Clinical and epizootological features.Animals are most often infected by ingesting food or water contaminated with Cl spores. chauvoei. Emkar usually occurs on pastures, more often in hot, dry summers. Under these conditions, animals, eating dry grass, simultaneously capture soil particles and, along with it, Cl spores. chauvoei. Emkar is a seasonal disease (summer, autumn), but sometimes sporadic cases of the disease are observed during the stall period as a result of feeding animals hay collected from meadows unaffected by emkar. The incubation period is most often 1-2 days, in some cases 5 days. The disease begins with a sharp increase in body temperature to 41-420C, depression, refusal of food, and cessation of chewing gum are noted. Rapidly increasing swelling appears on certain parts of the body (croup, lower back, neck, chest, submandibular region), and sometimes even in the oral cavity or pharynx. They are initially warm and painful, then with the cessation of blood circulation due to compression of the vessels by gases they become cold and painless. When palpated, a peculiar crunching sound (crepitation) is heard, and when cut, a dirty-brown foamy liquid flows out of them, with the smell of rancid oil. Among the general symptoms of the disease, attention is drawn to difficulty breathing and a sharp weakening of cardiac activity, pulse 100-120 beats per minute. Animals usually die within 1-2 days.
5. Pathological anatomy.An autopsy should be carried out as soon as possible after the death of the animal, since already 4 - 5 hours after this, rapid gas formation occurs throughout the gastrointestinal tract and affected muscle areas. Bloody fluid begins to ooze from the natural orifices. The most important and at the same time pathoanatomical changes specific to emkar are localized in the skeletal muscles. The affected muscles are riddled with black-red or black-brown hemorrhages, dry, porous due to the accumulation of gases in them. Sometimes among them there are dry, dull, light gray islands of bloodless dead tissue, such as an anemic infarction. The gas bubbles that give muscles their spongy, porous appearance are composed of H, CO2 and N.
When pressed, the muscles crunch, and when cut they make a hissing sound. Their cut surface, oxidizing in air, quickly takes on a light red tone. It is quite dry and porous, as a result of which it somewhat resembles tinder. However, when pressed, a foamy, bloody fluid separates from it. Intermuscular tissue is swollen, yellowish in color and has a mucous consistency. Like the musculature, it is partially emphysematous. Edema often moves from the intermuscular tissue to the subcutaneous tissue. The affected muscles emit a sour odor, reminiscent of rancid oil, and the surrounding normal muscles are pale (collateral anemia).
Histologically, a picture of waxy degeneration and coagulative necrosis of muscle fibers is established. The dry light gray islands mentioned above correspond to areas of coagulative necrosis. According to the picture of changes, this is necrosis of a toxic type with complete discoloration of the nuclei, but with preserved outlines of muscle fibers and even their transverse striations. Muscle fibers bordering normal muscle show signs of milder changes, such as granular and fatty degeneration.
In some places, the muscle fibers are sharply pushed apart and compressed by accumulated small and large gas bubbles. Everywhere between the fibers and their bundles there are banded hemorrhages and numerous bacilli of the noisy carbuncle. Microbes, in addition to the interstitium, are found in the blood capillaries. The interstitial tissue is greatly thickened, swollen, and in places saturated with hemorrhagic effusion. In the central areas of the affected muscles it is necrotic, and in the peripheral areas it is infiltrated with leukocytes.
The sequential development of the process in skeletal muscles (histogenesis) is presented in the following form. As soon as the bacilli of the emphysematous carbuncle reach the intermuscular tissue, they cause swelling and hemorrhage. This is followed by muscle degeneration and necrosis. The latter is also accompanied by tissue necrosis. Both degeneration and necrosis in equal measure and fiber are a consequence of the action of toxins of the causative agent emkar. The formation of gases is the last stage of the process. It occurs only after necrosis of the parenchyma and is the result of fermentation.
The degree of muscle damage, as well as its prevalence, varies greatly. In some cases, lesions are characterized by coverage of entire muscle groups, for example, limbs, croup, chest, while others are limited to only individual muscles. Finally, there are such weak muscle lesions in the form of small areas of hemorrhagic infiltration that searching for them is associated with great difficulties, and they can only be detected on parallel planar sections of the muscles.
The autopsy picture of animals that died from emkar is characterized by the following features. The corpse is usually very swollen, bloody foam is released from the nose (the result of agonal pulmonary edema), and bloody discharge from the anal and vaginal openings.
The subcutaneous tissue of the affected muscle area contains pale yellow serous infiltrates, riddled with hemorrhages and gas bubbles. In the serous cavities of the body, a reddish serous fluid is found, and onserous leaves - overlays of gray-red films of fibrin and gelatinous clots of coagulated protein. The serous membrane itself is stagnant -full-blooded, riddled with hemorrhages and diffusely colored purplish-red (imbibition redness).
The lymph nodes, especially the regional affected muscles, have a brain-like consistency (acute swelling), are saturated with serous-bloody fluid and are dotted with hemorrhages. The spleen is swollen, congested, slightly flabby, in most cases contains dry, black-red, well-circumscribed, dead foci of hemorrhagically infiltrated pulp. In appearance, they resemble a picture of altered muscles. Dry, dull, ocher-yellow lesions with small gas bubbles are often found in the liver. Most likely they are of postmortem origin, since these foci are absent in animals that were forcibly killed. The same as in the liver, focal changes are observed in the kidneys and adrenal glands.
The heart is in a state of parenchymal dystrophy, the myocardium is colored gray-yellowish, and is often riddled with hemorrhages. The musculature of the heart is dense, even sometimes hard, and colored black and red; its vessels are sharply filled with gelatin-like coagulated blood. This state of the heart is very pathognomonic for emkar. The blood in the heart and blood vessels is dark red and coagulated. The lungs are congestively hyperemic and edematous. The intestinal mucosa is hyperemic and covered with hemorrhages.
If the disease is acute and without specific changes in the muscles, the pathological picture has the character of toxemia, in which the typical pathological signs of the disease are absent.