Animal anatomy, histology, pathological anatomy

BIBLIOGRAPHY
1. Zharov A.V. Pathological anatomy of animals. – St. Petersburg; M.; Krasnodar: Lan, 2013. – 620 p. – Access mode: EBS “Lan” (http://e.lanbook.com), ISBN: 978-5-8114-1450-5 2. Zharov A.V. Forensic veterinary medicine. Textbook. – St. Petersburg; M.; Krasnodar: Lan, 2014. – 464 p.

LECTURE No. 9

Subject:VIRAL INFECTIONS. PATHOMORPHOLOGY OF SWINE AND BIRD FEVER.

Plan
1. Etiology, pathogenesis and pathological anatomy, diagnosis and comparative diagnosis of swine fever.
2. Etiology, pathogenesis and pathological anatomy, diagnosis and comparative diagnosis of rinderpest.
3. Etiology, pathogenesis and pathological anatomy, diagnosis and comparative diagnosis of avian plague.
Keywords:swine fever,hemorrhagic, necrotic, variegated marbled, hyperplastic, hemorrhage, petechiae, diphtheritic, conjunctivitis.
1. Swine fever (Pestis suum) is a viral infectious disease caused by hemorrhagic diathesis, fibrinous inflammation of the lungs and intestines. The disease can affect pigs of any age and different breeds. At different times of the year, animals can get sick, the disease spreads quickly, with an acute course, persistent fever, chronic course with lobar pneumonia or lobar-diphtheria inflammation of the colon.
Etiology and pathogenesis Pathogen The virus is highly sensitive. Pigs infect the patient mainly through elementary and aerogenic routes, but often endothelial cells of blood vessels and immune system organs are located in the lymph nodes, spleen and increase fibrinoid edema, which leads to fibrinoid necrosis and hyalinosis of the vascular walls.
Pathanatomy Swine fever occurs in the following forms: 1 - Septic form, in which pinpoint, spotty hemorrhages on the skin of the head, neck and abdominal cavity of pigs. Hemorrhagic exudate accumulates in the abdominal cavity of the chest and under the pericardium of the heart. 2- A form of pasteurellosis occurs in adult pigs, the disease lasts 10-15 days.
changes in which necrotizing inflammation of fibrin develops in the lungs, type 3 salmonellosis occurs in piglets aged 2-6 months, the disease lasts 1 month, with changes in the appearance of dehydrating inflammation in the intestines, button-shaped nodules form on the intestinal mucosa. 4- Mixed form, in which both forms of pasteurellosis and salmonellosis occur simultaneously.
Classical swine fever Classical (European) plague is a contagious disease caused by an RNA virus; Animals of all ages get sick. The acute manifestation of the disease is characterized by hemorrhagic diathesis, anemia of individual organs, and the development of hemorrhagic and sometimes diphtheritic inflammation. In its chronic course, the plague is complicated by a second bacterial infection (salmonellosis, pasteurellosis and other diseases), and then there is a layering of inflammatory, necrotic changes in the gastrointestinal tract, lungs in salmonellosis, pneumonia in pasteurellosis, and the accompanying microflora causes atypical forms of manifestation of the disease. The pathological picture of classical swine fever can be varied depending on the virulence of the pathogen, its passage through a susceptible organism, and the resistance of the organism. In plague, first of all, the organs of the hematopoietic apparatus are selectively affected. Hemorrhagic diathesis is caused by changes in vascular porosity. The virus enters the animal’s body through the nutritional route; penetrating through the mucous membranes, enters the blood. Circulating in the blood, it spreads throughout the body. The virus is resorbed by the endothelial cells of blood vessels, where it multiplies, while the endothelium swells and the cells exfoliate. In large vessels, hyalinization of the media occurs and infiltration of adventitia lymphoid cells occurs, which causes vascular spasm. Changes in the skin. Hemorrhages may be observed in the skin, mainly in its thinnest places; they have clear boundaries, different sizes, and the simultaneous development of cyanosis in the area of ​​the snout, ears, abdomen, and tail is possible. Hemorrhages are more often observed in piglets and gilts, and somewhat less frequently in adults. Necrosis is possible, mainly in areas of hemorrhage or damage. In chronic cases, a smallpox-like rash is observed. In the subcutaneous tissue and muscles, phenomena of congestive hyperemia, as well as hemorrhages, can be observed. Changes in the lymph nodes do not immediately affect their entire system. Certain packages are affected earlier and more often than others. So, first of all, the retropharyngeal, submandibular, cervical, renal, lumbar, gastric (lesser curvature) are affected. Then the mediastinal, bronchial and then the lymph nodes of the body, mesenteric. Sometimes regional nodes to the rectum are affected early. The lymph nodes are enlarged, red on the surface, somewhat compacted. At the beginning, the lymph node in the section is pale gray in color with a red rim. The cut surface is somewhat moist and bulges. In this case, lymphoid hyperplasia of the follicles and pulpal cords occurs. The presence of a red rim is due to the resorption of red blood cells by the endothelium of the cortical sinus, as well as the filling of the sinus itself with red blood cells. Subsequently, red blood cells begin to flow into the sinuses of the medulla of the lymph node. In this case, the lymph node acquires a motley-marbled, bloody appearance on the section. With a significant lesion during the height of the disease, hyperplastic follicles and pulpy cords in the form of pale gray foci are clearly visible on a dark red background; the cut surface is moist, with noticeable droplets of bloody fluid on it. In such cases, the cut surface resembles Krakow sausage. Such lymph nodes are in a state of hemorrhagic inflammation. It should be borne in mind that individual lymph nodes in places of trauma (where an animal was stabbed in the neck area) or organ hemorrhages may have a similar mottled marble appearance. However, in this case, hyperplasia of the nodes does not occur, and their cut surface is smooth, not convex, and only nodes regional to the site of injury are affected. In most cases, the spleen in plague is colored paler than usual, the volume is not changed, sometimes slightly enlarged, as if swollen due to hyperplasia. Characteristic is the presence of hemorrhagic infarctions, which occur in no more than 40% of cases. Their most typical location is along the edges of the organ in the form of cone-shaped elevations, but they can also have a round shape and be located throughout the spleen. It should be taken into account that infarctions in the spleen can sometimes occur in other diseases, such as the septic manifestation of salmonellosis, streptococcal embolism, swine erysipelas, and bacterial sepsis. The formation of infarctions occurs due to the fixation of the virus on the walls of the terminal arteries, followed by thrombosis. In the heart, hemorrhages are observed mainly under the epicardium, more often in the atria, and also under the endocardium. However, hemorrhages under the endocardium in isolation should not be given diagnostic significance, since they can be of agonal origin; striped, spotted hemorrhages especially often appear during the slaughter of even clinically healthy pigs. No changes are usually found in the myocardium during plague. Changes in the breathing apparatus. There is anemia in the mucous membrane of the larynx with hemorrhages in it, less often in the trachea and bronchi. In the lungs, hemorrhages under the pulmonary and under the costal pleura are often observed. However, hemorrhages under the pleura can also occur in other septic diseases. Hemorrhages in the interlobular tissue of the lungs are pathognomonic for plague, but they are not always clearly visible. It should be borne in mind that inflammation in the lungs depends not so much on the virulence of the virus, but on the secondary microflora developing in them, and most of all on the conditions in which sick pigs are kept. Changes in the organs of the urinary system are often observed. A typical picture in the kidneys is anemia, especially of the cortex, and pinpoint hemorrhages against a pale background. However, the kidneys may have a normal appearance, and diffuse hemorrhages are found in the medulla, pelvis, which simulate hemorrhagic nephritis. Very rarely, infarcts occur in the cortex. The mucous membrane of the bladder is anemic, with hemorrhages of various sizes; in very rare cases, hemorrhagic cystitis is observed. Sometimes there may be hemorrhages on a pale background in the mucous membrane of the ureters. Changes in the digestive system are localized mainly in the stomach and large intestine. In acute cases, hemorrhages are often observed, both in the serous and mucous membranes in different parts of the digestive tract, almost always they are observed in the rectal mucosa. At the onset of the disease, catarrhal inflammation of the gastric mucosa with hemorrhages in it is often noted. At the height of the disease, hemorrhagic, rarely diphtheritic gastrocolitis appears. The liver is in a state of granular degeneration, sometimes there are hemorrhages under the capsule and in the mucous membrane of the gallbladder. There may be hemorrhages in the brain, both in its membranes and in the substance itself. Histological examination reveals non-purulent encephalitis in the form of perivasculitis. In plague complicated by salmonellosis, acute septic changes are less pronounced, diphtheritic changes intensify: necrotizing lesions in the gastrointestinal tract, and changes in the lungs are layered. The most constant changes are in the cecum and colon, less often in the stomach. There is diffuse diphtheritic inflammation in the mucous membrane with transition to necrosis. With chronic manifestations, dense formations (buds) resembling buttons may appear in the mucous membrane of the large intestine. They are grayish-brownish in color, round in shape, up to 1.5 cm in diameter, protrude into the intestinal lumen, with a well-defined concentric structure, tightly held in the intestinal wall. In the center of the bud, as a result of necrosis, there is a small brown depression. Usually they are not scraped off; they arise mainly at the site of inflamed solitary follicles. Small necrotic lesions sometimes appear in the liver. In cases of complications of plague with salmonellosis, it is also possible to develop more often catarrhal bronchopneumonia. When plague is complicated by pasteurellosis in acute and subacute cases, the septic picture may intensify, and hemorrhagic lymphadenitis is clearly visible. With chronic manifestations, fibrinous pneumonia with swelling of the interlobular connective tissue is observed. Pneumonia can acquire a fibrinous-hemorrhagic character with foci of necrosis. Fibrinous or serous fibrinous pleurisy and pericarditis often develop. Making a diagnosis of plague requires a comprehensive study of the epizootic picture, it is necessary to open it as much as possible, and in some cases it is necessary to carry out a diagnostic slaughter of animals suspected of the disease and conduct a bacteriological study. It should be remembered that the post-vaccination reaction in the first 2-3 weeks may resemble the pathological picture of acute classical swine fever. 17.2. African swine fever African swine fever, or East African swine fever, caused by a DNA virus. The disease is highly contagious, the entire herd becomes ill within 2-3 days, is acute, and has a mortality rate of 90-95%. The disease is characterized by fever, hemorrhages in the lymph nodes, kidneys, and intestines; has great similarities with ordinary plague. With African plague, mothers die earlier than their offspring; young animals are characterized by agitation and paresis of the hind limbs. Pathological changes, as well as clinical ones, are very similar to the European plague, but there are some differences. Red spots are often observed in the skin or it is diffusely red with a bluish tint, and hemorrhages are noted. The subcutaneous tissue is often edematous, subicteric, often with hemorrhages. Serous-hemorrhagic effusion, sometimes with the presence of fibrin, is often observed in the chest and abdominal cavities. The lymph nodes, especially the gastric and hepatic ones, are enlarged, dark blue, often black, and drops of blood appear on the cut surface. The spleen is enlarged due to parenchymal edema; large, isolated hemorrhagic infarctions are characteristic. There are extensive subepicardial hemorrhages in the heart, predominantly occupying a significant part of the surface of the left ventricle. In the lungs there is venous congestion, edema, hemorrhages in the parenchyma, areas of atelectasis and bronchopneumonia are often observed, often accompanied by the development of necrosis of the pulmonary parenchyma due to thrombosis of the pulmonary veins. In the kidneys, multiple small, spotty hemorrhages are observed throughout the parenchyma of the cortex and medulla, in the renal pelvis. The bladder with single petechiae in the mucous membrane or is not changed. Lesions in the digestive system manifest themselves in the form of hemorrhagic gastritis, in the intestine there is diphtheritic inflammation with hemorrhages in the mucous membrane and submucosal edema of the rectal wall. There is swelling in the liver. In the gallbladder there is swelling of the wall and hemorrhages under the serous membrane. Minor hemorrhages, non-purulent encephalitis are observed in the brain, and vascular thrombosis is possible. Making a diagnosis of African plague, as well as European plague, requires a comprehensive study of the epizootological, pathological and anatomical picture and bacteriological research data, and in some cases, a biological test on pigs. Rinderpest (Pestis bovina) and carnivore plague (Febris catarrhalis infectiosa canis) Causative agent: RNA virus from the genus Morbillivirus, family. Paramyxoviridae. The infectious nature was established in 1711, then confirmed in 1895-1896. The pathogen was discovered in 1902. The virus is not very resistant in the external environment and to various physicochemical factors. At a temperature of 60°C it is inactivated within 15-20 minutes, when boiling - instantly; At room temperature it lasts for 4-6 days, at a temperature of 4°C - for several weeks, at a temperature of 20°C - for 6-8 days, in lyophilized form - for several years. When rotting, the virus is destroyed within 1-5 hours; disinfectants, alkalis, acids in 1-2% concentrations deactivate the virus within a few minutes. Epizootology. Cattle, buffaloes, zebu are susceptible; sheep, goats, camels, and wild animals are less susceptible. Among laboratory animals, rabbits and dogs are susceptible to various applications of the virus. Source of pathogen: sick and recovered animals. Routes of transmission: nutritional and aerogenic. Transmission factors: feed, water, care items. Incubation period: 3-17 days. in cattle; 2—14 days. in sheep; 5-7 days. from camels. Symptoms In acute cases - persistent fever, temperature 41-42°C with minor remissions, on the first day - dry cough, agitation, then depression, loss of appetite, ruffled fur, inflammation of the mucous membranes of the eyes, nose, mouth, gray-yellow nodules, transforming after disintegration into a pasty mass in the form of a film with an ichorous odor, in place of ulcer nodules with uneven edges. By the 5th day, the oral mucosa has an eroded, bleeding surface, covered with necrotic tissue with fibrin. There is drooling, conjunctivitis, purulent vaginitis. Pathological changes. Exhaustion, hemorrhagic diathesis, necrosis of mucous membranes and lymphoid tissues, necrosis and erosion in the oral cavity, purulent fibrinous plaque and ulcers in the intestines, fatty degeneration of the liver, lymph nodes are inflamed, hyperemic, there are foci of necrosis in them, brown bile with an ichorous odor. Diagnostics. Blood, prescapular and mesenteric lymph nodes, and spleen are sent to the laboratory. Laboratory studies include bioassay, isolation of the pathogen in cell culture, RSC, RDP, immunofluorescence. Differential diagnosis. The plague is distinguished from malignant catarrhal fever, which is characterized by damage to the eyes (keratitis, accumulation of exudate in the anterior chamber of the eyes), specific damage to the nasal and adnexal cavities of the skull. Foot and mouth disease is characterized by higher contagiousness, aphthous lesions of the oral cavity, the skin of the interhoof area, and the udder. The course of the disease is benign with low mortality, there is no damage to the hematopoietic organs. Viral diarrhea is characterized by less contagiousness, slow development of enzootic disease, and low mortality. Pasteurellosis is differentiated by the absence of damage to the oral mucosa and the detection of pasteurella during bacteriological examination. Hemosporidosis is diagnosed based on microscopic examination of blood smears. Prevention and treatment. Treatment of sick animals is prohibited by veterinary legislation. They are killed using a bloodless method, followed by burning of the corpses. For active immunization, a dry virus vaccine is used. Canine distemper (Febris catarrhalis infectiosa canis), canine distemper, Kare's disease is an acute viral disease of animals of the canine and mustelid families, characterized by fever, catarrhal inflammation of the mucous membranes, pneumonia, dysfunction of the nervous system and gastrointestinal tract. Widely distributed mortality rate 30-60%. The causative agent of the disease is immunologically and morphologically similar to the human measles virus and rinderpest virus. Epizootology.
The diagnosis is made on the basis of epizootological, clinical, pathological, and microbiological studies. For pathological diagnosis, it is necessary to dissect several pig carcasses.
Swine fever should be distinguished from pasteurellosis, salmonellosis, balantidiasis (a parasitic disease), viral gastroenteritis, measles, viral pneumonia, and Aueszky's disease.
2) Rinderpest (Pestis bovina) is an acute contagious infectious disease characterized by damage to the digestive tract. The disease occurs at any time of the year; sheep and goats are also infected; the disease occurs in a very mild form.
Etiology and pathogenesis. The disease is caused by a virus. The virus enters the body through the digestive and airways and penetrates the epithelial cells of the mucous membranes, multiplies, and then enters the bloodstream and spreads throughout the body, causing acute inflammation of the mucous membranes.
Pathological Anatomy In cattle, bleeding occurs in the mucous membranes of the mouth, throat, esophagus and gastrointestinal tract, these changes result from catarrhal hemorrhagic inflammation. Lymph nodes and spleen are enlarged, parenchymal organs are characterized by hyperemia and dystrophy.
Diagnosis. The diagnosis is made based on clinical signs of the disease, virological studies and pathological changes.
The disease should be distinguished from proteinuria, dangerous catarrhal fever, stomatitis, gastroenteritis and viral diarrhea. The plague differs from these diseases in its causative agent.
3). Classical fowl plague (Pestis gallinarium) is an acute contagious disease, a septic disease in which chickens, caesarean sections, turkeys belonging to the chicken family become sick and ultimately lead to 100% death of birds. Waterfowl (geese, ducks) and wild birds (sparrows, nightingales, etc.) are also contagious.
Etiology and pathogenesis of the causative agent of the virus. The virus enters the body through aerogenesis, elemental and cloaca.
From the mucous membranes and damaged areas of the skin, the virus enters the bloodstream and enters red blood cells, where it multiplies and spreads throughout the body, producing toxins and damaging the vascular wall. The concentration of the virus in blood serum, brain tissue, spleen, and lungs is very high.
Pathological Anatomy The following changes are observed in dead chickens. Patchy hemorrhages appear on the crown, scalp, neck and legs of birds. We also see hemorrhages in the internal organs. The disease is characterized by lightning-fast formation of pinpoint hemorrhages only in the epicardium of the heart. The most characteristic change characteristic of the disease is the appearance of hemorrhage in the form of a belt at the border of the glandular and muscular stomach. The lungs are full and swollen.
Diagnosis. It is burned on the basis of clinical, epizootological, pathological and virological studies. Fowl plague should be distinguished from Newcastle disease, pasteurellosis, and infectious laryngotracheitis.