The causative agent of avian leukemia belongs to the family. Diagnosis and forms of avian leukemia. Connective tissue tumors

Avian leukemia (Leucosis avium), leukemia, leukemia, hemablastosis. - a viral disease of a tumor nature, accompanied by a progressive pathological proliferation of hematopoietic tissue, both in the hematopoietic organs and beyond.

History reference. For the first time in chickens, leukemic changes were described by the Italian scientist V. Canarini in 1896. Later, in 1908, the Danish scientists V. Ellerman and O. Bang were engaged in the study of avian leukemia. They experimentally established the transplantability of myeloid and erythroid leukemia from sick healthy chickens with blood, tissue emulsion and cell-free filtrates. In 1921, V. Ellerman replaced the name of the disease leukemia with the term "leukemia", described 3 forms of bird leukemia in chickens; aleukemic extravascular lymphoid leukemia, leukemic and aleukemic myeloid leukemia and erythroid (intravascular lymphoid) leukemia. In the late 1930s, the relationship between leukemia and tumors of various types was experimentally established.

Further studies have shown that viral strains have the ability to induce not only the original disease, but also cause various sarcomas, osteopetrosis and neurolymphomatosis. As a result, researchers began to believe that these diseases have the same etiology.

Based on the foregoing, in 1941, American researchers combined leukemia, myelocytoma, fibrosarcoma, endothelioma, osteopetrosis and neurolymphomatosis into the “avian leukemia complex”. They also introduced the term "lymphomatosis" to refer to lesions that are manifested by the multiplication of tumor lymphoid cells, regardless of whether they form tumor nodes or are focally diffusely scattered throughout the tissues of various organs.

To date, the following classification of avian leukemia has been stopped:

• lymphoid leukemia;
• meloid leukemia (myeloblastosis);
• erythroid lecosis (erythroblastosis).

The spread of avian leukemia is usually found in countries with developed industrial poultry farming.

Avian leukemia causes significant economic damage to poultry farms, which consists of losses from the loss of poultry, reduced egg production, sanitary rejection of affected carcasses, as well as the cost of disease control measures.

In Russia, for the first time, a case of avian leukemia was described by N.A. Soshestvensky in 1908. In the 1930s, avian leukemia began to be diagnosed in many regions of the country. At the same time, the loss of chickens from leukemia in individual poultry farms ranges from tenths of a percent to 7-12%, and sometimes up to 30 percent or more of the number of autopsied corpses. The most common is lymphoid leukemia (lymphomatosis).

Etiology. Leukemia in birds is caused by a filter virus. A large number of viral strains of transplanted forms of avian leukemia have been isolated. These viruses are divided into 3 subgroups: A, B and C. Subgroup A includes viral strains RAV -1, RAV -3, RAV-4, RAV -5, FAV -1, FMV -1, RIF-1, RPL-12 , SR-RSV-1, MN-RSV-2, NA-RSV; to subgroup B –RAV-2, AMV-2, RIF-2, SR-RSV-2, NA-RSV; to subgroup C –CL-RSV, PR-RSV.

In sick birds, the virus was found in the blood, in extracts from organs and in feces. Outwardly healthy chickens can also keep it in a latent state and pass it on to their offspring.

Leukemia viruses quickly lose their activity at high temperatures, at 46°C and above. When heated to 70°C, the leukemia virus is inactivated in 30 minutes, at 85°C in 10 seconds.

epizootology. Bird leukemia affects mainly chickens, less often turkeys, guinea fowls, ducks and geese. Cases of leukemia in pheasants, parrots and ostriches are described. The source of infection are clinically ill and outwardly healthy chickens - virus carriers. Transmission of infection occurs mainly through eggs, less often by aerogenic and alimentary routes. Chickens are most susceptible to the leukemia virus in the first 40 days of their life, and the first clinical signs are noted in chickens mainly older than 4 months. From the body of a bird, the virus is excreted with saliva, excrement and with an egg.

Predisposing to the occurrence of leukemia in birds is the lack of a properly balanced protein-vitamin and mineral complex of substances in the feed, as well as violations of the zoohygienic parameters of the microclimate in the poultry house, crowded content.

Pathogenesis. Leukemia is characterized by progressive growth of hematopoietic tissue in the hematopoietic organs and beyond. The source of pathological hematopoiesis in birds are poorly differentiated elements of connective tissue. As a result of excessive proliferation and metaplasia of these cells, leukemic tissue growths are formed in the organs in the form of infiltrates, foci and nodes, resulting in an increase in the volume of the affected organ. Immature forms of leukocytes and erythrocytes enter the blood vessels in large quantities (leukemic leukemia). In an individual bird, the blood may be within the normal range (alukemic leukemia).

According to the type of cells multiplying in the organs, it is customary to distinguish the following forms of leukemia: reticulosis, hemocytoblastosis, erythroid, myeloid, lymphoid leukemia and others. The development of a particular form of leukemia in a bird depends on the type of reaction of the bird's body. The nature of the reactivity of the host is also influenced by genetic factors, the age of the chickens at the time of their infection, the method of infection and the dose of the virus that entered the body of the bird.

An important factor that has a significant impact on the host response is the age of the bird at the time of exposure to the virus. It has been found that chickens at 3 days of age are about 50 times more susceptible to BAI-A than birds at 21 days of age. The type of infection also influences the occurrence of leukemia. Erythroblastosis and myeloblastosis often occurs in chickens with intravenous and bone marrow infection. Lymphoid tissue is considered the most sensitive to the effects of the virus; this explains the predominance of the lymphoid form of avian leukemia under natural conditions.

Immunity. It has been experimentally proven that avian leukemia produces 2 types of immunity - immunity to infection with a virus and immunity to inoculation of leukemic tissue. Specific antigens of viral and tissue origin were found in leukemic cells. Antibodies that neutralize the virus were found in the blood plasma of chickens. Despite the detection of virus-neutralizing antibodies in the blood of chickens, all attempts at artificial immunization against chicken leukemia have so far been unsuccessful.

Clinical picture. Leukemia in birds is chronic. There are 2 stages of avian leukemia: long-term subclinical and short-term clinical, which in birds ends in death. Clinical signs of avian leukemia are not typical. The incubation period lasts from 2-9 days to several months. In severe cases of manifestation of the disease in a sick bird, we register exhaustion, lethargy, drowsiness, and diarrhea. The comb is pale with an icteric tinge or cyanotic. The abdominal region of a bird is often enlarged, by palpation a veterinarian can establish enlarged organs and dense nodes of neoplasms, the liver protrudes beyond the edges of the ribs and sternum. With damage to the intestines and mesentery, the veterinarian sometimes notes dropsy of the abdominal cavity; sick chickens take the penguin pose.

When examining blood samples, the blood picture is not always characteristic of avian leukemia. In avian leukemic lymphoid leukemia, we sometimes note an increase in the number of lymphoblasts; lymphocytes and pseudoeosinophils over 100,000. When examining the bone marrow, it is dominated by lymphoblasts, prolymphoblasts and lymphocytes. In leukemic and reticuloendothelial forms of avian leukemia, in the blood and bone marrow punctate, the number of monocytic and pseudoeosinophilic leukocytes at various stages of their differentiation is increased.

Erythroblastosis, hemocytoblastosis and myeloblastosis are manifested by blast crises and spontaneous remissions (VM Kaluyna, 1967). With erythroblastosis, an increase in the number of erythroblasts in the peripheral blood and bone marrow (up to 90%) is specific, the number of erythrocytes decreases to 0.5 million, hemoglobin by 1.5 g /%, the platelet count is reduced. For hemocytoblastosis, excessive reproduction of hemocytoblasts is characteristic. In avian leukemic myeloid leukemia, the content of myeloblasts, promyelocytes, metamyelocytes and myelocytes is increased in the circulating blood and bone marrow. The disease lasts from several days to a year, depending on the form of manifestation of bird leukemia.

The outcome of the disease is usually fatal.

Pathological changes. With lymphoid leukemia, changes typical for this form of leukemia are found in the liver, spleen, kidneys, less often in other organs and skin. There are diffuse and nodular lesions of parenchymal organs. Both forms of the disease in poultry occur as a systemic disease. With systemic (generalized) lymphoid leukemia, the liver is enlarged several times and often occupies the entire abdominal cavity. The proportions of the affected liver are enlarged unevenly. Depending on the blood supply and the development of dystrophic and proliferative processes in the liver, its color is gray-red or yellow-gray. The consistency of the liver is dense, or flabby, easily torn when pressed, we register hemorrhages under the capsule.

With diffuse damage, the surface of the liver is smooth. With numerous punctate or larger grayish-white foci; with a nodular lesion - sarc-like nodes of various sizes of various sizes protrude on the surface. In both cases, lesions penetrate deep into the parenchyma of the organ.

The spleen is normal or slightly enlarged, bluish-red, sometimes grayish-red, with numerous grayish-white foci and nodules. The kidneys, as a result of the formation of nodules of various shapes on them, have a red-gray color. Nodular lesions of a leukemic nature can also be in other organs.

myeloid leukemia in birds it is relatively rare and is accompanied by a predominant lesion of the liver, spleen, kidneys and ovary. If the course of leukemia is acute, then veterinarians do not register changes in these organs. In the chronic course of the disease, we note anemia with mild icterus of the visible mucous membranes. The liver is enlarged, reddish-brown in color, with numerous dotted whitish foci, or larger knots of whitish-gray tissue are detected, the consistency is flabby, the tissue is easily torn when pressed. The spleen is enlarged, bluish-red. In the kidneys we find nodes of various sizes. The bone marrow is watery, light red in color, with small hemorrhages. Other changes include ascites, hydropericarditis, anasarca (swelling of the subcutaneous tissue), hemorrhages in various organs. In a separate sick bird, we note ruptures of the liver and ovary with abdominal hemorrhages.

Reticuloendothelial leukemia in a bird with leukemia, it is accompanied by hyperplastic processes in the stroma of parenchymal organs. This type of leukemia at autopsy is more often recorded in young chickens and turkeys. The dominant cellular elements are histiocytes. Opening these chickens, the veterinarian finds cyanosis of the skin appendages of the head, often exhaustion, sometimes dropsy of the abdominal cavity. The liver is enlarged, grayish-red or cherry-red, with dotted grayish-white foci, which may be in the form of nodules. The consistency of the liver is dense, its tissue is easily torn (even broken). In an individual bird, at autopsy, we find intravital ruptures of the liver, followed by hemorrhage into the abdominal cavity. The spleen is greyish-red, with whitish gray foci. The bone marrow is dark red.

erythroid leukemia rarely seen in birds. Pathological anatomical picture in this form of leukemia is poorly expressed. Visible mucous membranes are anemic and icteric. Hemorrhages occur under the skin and in the internal organs. Parenchymal organs are enlarged, with finely punctate light gray foci. In an individual bird, we note ascites. The bone marrow is liquefied.

Diagnosis for leukemia is put in a complex way, using virological, epizootological, clinical and pathoanatomical methods. Decisive in the diagnosis is pathoanatomical autopsy. The histological method is used to determine the form of leukemia. Serological reactions have been developed to detect a group-specific antigen of viruses of the leukemia-sarcoma group: RSK, CoFAL - test, immunofluorescence test - TsSHP, RNGA with a drug for the diagnosis of avian leukemia (PDLP) proposed by P. Zelensky. To identify type-specific antigens and antibodies, the RIF test and the centralization reaction are used.

Differential Diagnosis. Leukemia in birds (hemoblastosis) must be differentiated from coligranulomatosis, hepatitis, uric acid diathesis, sarcomas, carcinomas.

In Marek's disease in a dead bird, we find formations similar to leukemia in parenchymal organs. Marek's disease occurs suddenly and affects young animals aged 1-5 months. The pathological process often involves the lungs, ovary, glandular stomach and skin.

Tuberculosis often affects the liver, spleen, bone marrow and intestines. Tuberculous nodes in a dead bird have the ability to merge into larger ones (coglomerates), and are often colored gray-yellow, the center of such nodes usually undergoes melting. With leukemia, these lesions have a greasy color and consistency.

With coligranulomatosis, typical changes are found in the liver and in the places where the caecum branches. The color of these formations is yellow, the appearance is granular, we often note layering in the section; granules, merging, often form conglomerating forms of a dense consistency.

Treatment has not been developed.

Prevention and control measures. There are no effective measures to combat avian leukemia. To prevent the introduction of infection into the farm, it is necessary to purchase eggs and chickens for breeding purposes only in farms. Leucosis-free birds. It is necessary to strictly observe the isolated keeping of chickens by age groups, especially during the first four weeks. Veterinarians should regularly inspect the poultry population and promptly identify chickens that are suspected of having avian leukemia. Create the best conditions for keeping and feeding birds. Veterinary and sanitary measures are systematically carried out (regular cleaning and disinfection of inventory, premises and walking areas for birds, etc.). The selection method seeks to obtain lines of chickens resistant to avian leukemia. Poultry farms that are unfavorable for avian leukemia are difficult to improve by one culling of chickens and hens suspected of having leukemia. Only the replacement of the entire poultry population with new families or lines of chickens from farms that are free from leukemia can give the desired result.

In the absence of anemia or jaundice and changes in the muscles, the liver, spleen and other affected organs of the sick bird are disposed of, and the carcass is rendered harmless by boiling. Carcasses of chickens with altered muscles are sent for technical disposal.

Avian leukemia(Leucosis avium), hemoblastosis, leukemia, leukemia, a viral disease characterized by systemic tumor growths of hematopoietic tissue. Avian leukemia registered in all countries with developed poultry farming. Economic damage is associated with the death of birds, a decrease in egg production, the rejection of carcasses, and restrictive measures.

Etiology. The causative agents of avian leukemia are RNA-containing oncornaviruses of the Retraviridae family that cause leukemia and sarcomas in birds and include 6 antigenic subgroups - A, B, C, D, E, F (see Tumor viruses). Viruses of this group are found in tumor tissue, blood, parenchymal organs, and also in chicken eggs. Viruses are most stable in a neutral medium, inactivated by ether, chloroform, saponin, thermolabile (rapidly inactivated at t 46°C), passaged on cultures of chicken embryo fibroblasts (FEC).

Epizootology. L. p. is established in chickens, turkeys, guinea fowls, geese and ducks, as well as (isolated cases) in pheasants, pigeons, parrots, canaries, finches, quails, cranes, storks, gulls, ostriches, eagles, swans. Chickens get sick more often. Sources of the causative agent of infection are sick and clinically healthy virus-carrying birds. Avian leukemia It is usually transmitted through the hatching egg, but alimentary or aerogenic infection of chickens, which are much more susceptible to adult chickens, is not excluded. The disease appears (mostly sporadically) in birds older than 4 months, but sometimes in 2-3 month old chicks. Known genetically determined increased susceptibility to leukemia of chickens of certain breeds and lines. The emergence and spread of L. p. is facilitated by the crowded keeping of birds, the imbalance of diets in digestible protein, vitamins and minerals, and the autoclaving of feed.

The pathogenesis is not well understood. It has been established that avian leukemia disrupts the processes of normal maturation and differentiation of hematopoietic cells, excessive reproduction of cellular elements occurs not only in the hematopoietic tissue, but also outside it, especially in organs rich in RES cells. Depending on the cellular composition of tumor growths, lymphoid, myeloid, erythroblastic leukemia (erythroblastosis), as well as hemocytoblastosis and reticuloendotheliosis are distinguished.

Immunity. Despite the detection of virus-neutralizing antibodies in the blood of chickens, attempts at artificial immunization against avian leukrosis have so far been unsuccessful.

Course and symptoms. Avian leukemia runs chronically. There are 2 stages of avian leukemia: long-term subclinical and short-term clinical, ending in death. Manifestations of the disease are not specific: lethargy, diarrhea, exhaustion. Sometimes it is possible to palpate an enlarged liver, there may be dropsy of the abdominal cavity. Erythroblastosis is characterized by a decrease in hemoglobin content, an increase in the number of erythroblasts, proerythroblasts and normoblasts in the peripheral blood and bone marrow. With lymphoid L. p., against the background of a decrease in the number of erythrocytes, the number of cells of the lymphoid series increases, with myeloid leukemia of birds. In the peripheral blood and bone marrow, cells of the myeloid series predominate - from myeloblasts to pseudoeosinophils. With reticuloendotheliosis, lymphopenia, an increase in the number of myeloid cells, monocytes, and reticular cells are noted.

pathological changes. For lymphoid, myeloid leukemia of birds and reticuloendotheliosis, a significant increase in the liver is characteristic. On the grayish-brown surface of the organ, gray-white areas of various sizes are visible, greasy on the cut. The kidneys and spleen are also enlarged and anemic. An enlarged ovary may look like a cauliflower. Grayish-white foci can be in the stomach, bursa of Fabricius, lungs, and other organs. With erythroblastosis, a sharp pallor of the skin and muscles is noted. The liver, spleen, kidneys are reddish in color, swollen, but slightly enlarged. Small hemorrhages are visible under the serous membranes. Histological examination in lymphoid leukemia in the liver, kidneys, spleen, ovary and other organs reveals diffuse or focal growths of immature lymphoid cells, in myeloid - damage to the bone marrow (normal hematopoietic tissue is replaced by pathological) and proliferation of myeloid cells in organs. Reticuloendotheliosis is characterized by proliferation of poorly differentiated reticular cells and adventitia of blood vessels of various organs. With erythroblastosis, a large number of immature red blood cells (proerythroblasts, basophilic erythrocytes) are found in the sinuses of the bone marrow, spleen, capillaries of the liver, and kidneys. Hemocytoblastosis is characterized by peri- and intravascular accumulation of hemocytoblasts.

Diagnosis. A decisive role in the diagnosis of avian leukemia is played by pathomorphological studies of the affected organs. The disease cannot be established by clinical signs. Hematological studies, which are of some value in detecting erythroblastosis and avian lymphoid leukemia, cannot be carried out on a large scale. Serological tests have been developed to detect a group-specific antigen of viruses of the leukemia-sarcoma group: RSK, cofal test, immunofluorescence reaction, RNHA with a drug for the diagnosis of L. p. (PDLP) proposed by V. P. Zelensky. To identify type-specific antigens and antibodies, a RIF test and a neutralization reaction are used. Avian leukemia differentiate from tuberculosis, Marek's disease, pullorosis - typhoid, coligranulomatosis, hepatitis, uric acid diathesis, sarcomas, carcinomas.

Treatment has not been developed.

Prevention and control measures. Hatching eggs and breeding birds should be imported from obviously prosperous farms; only strong, viable chickens are transferred to the breeding workshops. The conditions of keeping and feeding must comply with the requirements established for birds of each age, direction and level of productivity. Mandatory is the isolated rearing of chickens of different age groups, regular culling of sick and weak chickens and hens, autopsy of all dead and forcedly killed birds, histological examination of pathological material in cases of suspected avian leukemia. In farms that are unfavorable for L. p., it is recommended to use eggs from hens older than 1 year for incubation, to create broodstock from linear-hybrid birds that are genetically resistant to L. p. Recommendations have been developed for breeding leukemia-free chickens.

Leukemia(lat. -Leukosisavium; English -Leukosis; hemoblastosis, leukemia, leukemia, hepatolimphomatosis, lymphoblastosis) is a neoplastic disease characterized by systemic tumor-like growths of hematopoietic tissue, occurring in four forms: lymphoid, myeloid, hemocytoblastic and erythroid.

Historical background t R a nence, with t epen op a demolition t and and damage. The lymphoid form of leukemia was established by Rolofem in 1868, Caparini described leukemia in 1896, Batgerfeld called these diseases aleukemic lymphadenoma. The viral nature of the disease was proved by Burmeister and Purhaz.

Chicken leukemia occurs in all countries with developed poultry farming and causes enormous economic damage due to the death of 10...27% of poultry, a sharp decrease in egg productivity - by 20...30%.

The causative agent of the disease. Leukemia viruses belong to the family Retroviridae and include several varieties. All viruses of the leukemic-sarcomatous complex are divided by antigen into six groups (A, B, C, D, E, F). Under natural conditions, type A viruses are most common, less often - B and C.

Rous sarcoma virus can be cultured on the chorion-allantoic membrane of a chicken embryo with the formation of large and small plaques. The lymphomatosis virus multiplies in the cell culture of chicken fibroblasts, without exerting a cytopathogenic effect. When chicken embryos are infected with myeloblastosis virus, 100% of hatched chickens develop leukemia. The erythroblastosis virus contained in the bone marrow of chickens after infection of chicken embryos causes the erythroid form of leukemia in them.

Cells affected by oncornaviruses can be divided into three groups: virus-producing, virogenic, and non-producing. It is possible to prove the presence of a leukemia antigen using the COFAL test (complement fixation of avian leukemia), as well as by setting the RIF test (resistance-inducing factor).

Leukemia viruses are rapidly inactivated at 46°C. To conventional disinfectants (chlorine-containing, formaldehyde, soda ash), the leukemia virus is unstable and quickly dies.

Epizootology. Lymphoid leukemia (lymphomatosis) occurs with the formation of tumors from lymphoblasts in the organs and tissues of the body. Chickens are susceptible to the disease, less often turkeys, ducks, geese, parrots and birds of other species.

Epizootologically, this disease is widespread. In some poultry farms, antibodies are found in 75% of chickens. Adult chickens get sick with lymphoid leukemia, less often chickens at 4 ... 5 months of age. Infection occurs transovarially from chickens carrying the virus.

Myeloid leukemia (myeloblastosis) occurs in 1.5...2% of cases. It is characterized by leukemia and the formation of myelocytes in the organs. Chickens, turkeys, guinea fowls, pheasants are susceptible to the disease. Sick, as a rule, an adult bird.

Reticuloendotheliosis - hemoblastosis is characterized by the formation of lymphosarcomas from histiocytic cells in organs and tissues. Young chickens, turkeys are sick, and in experiments it was possible to infect ducks, geese, pheasants and quails. The extent of the spread of the disease is not well understood.

The erythroid form of leukemia (erythroblastosis) has two varieties: proliferative and anemic. The proliferative form is accompanied by anemia, jaundice of the mucous membranes, earrings, subcutaneous fat; the anemic form is characterized by anemia of parenchymal organs (liver, spleen, kidneys).

Avian leukemia in isolated cases occurs in various systems of keeping, but in some poultry farms it is widespread. Especially often leukemia is registered in farms with industrial poultry breeding, where the leading role is given to

587 one-sided selection of poultry for productivity, without taking into account its resistance to leukemia. Poultry imported from breeding farms to industrial farms, under unfavorable conditions of feeding and keeping, is especially sensitive to leukemia. During the period of the bird getting used to new conditions, the number of cases of leukemia increases.

Pa t genesis. The pathogenesis of lymphoid leukemia is closely related to the bursa-dependent lymphoid system. After bursectomy, there is a significant suppression and even complete cessation of the growth of lymphoid tumors.

Under natural conditions, after infection of sensitive chickens, the virus reproduces in many tissues and organs. Significantly earlier than the end of the incubation period, after 1-2 months from the moment of infection of the chickens, changes appear in the Fabricius bag, which are detected only by microscopic examination. As a result of the impact of the virus on target lymphoid cells, the latter are transformed into tumor lymphoblasts. In a significant amount, they accumulate in the central zone of one or more follicles of the Fabrician bag. The development of subsequent changes does not occur until the puberty of the chickens.

4–5 months after the onset of the primary affect, transformed lymphoblastic cells begin to actively multiply in the bursa of Fabricius, resulting in the formation of tumor nodules, the size of which ranges from the size of a millet grain to a walnut or more. Simultaneously with the growth of the primary tumor, metastasis of tumor cells occurs. This leads to the formation of daughter tumors in different organs.

Course and clinical manifestation. The main manifestations of avian leukemia are presented in Table 8.5.

8.5. Charak t eris t bird leukemia

pathological signs. Pathologically, there are two types of lesions in lymphoid leukemia: diffuse and nodular, the latter are similar to real tumors. With a diffuse lesion, the symmetry of the organ is preserved, with a focal lesion, it is broken.

The bursa of Fabricius is thickened and slightly enlarged at the onset of the disease; single grayish-white sebaceous tumor neoplasms are found on incision. Neoplasmic tissue of the bag metastasizes to other organs.

The liver with diffuse lesions is enlarged several times, its mass reaches 350 ... 500, sometimes 800 g. The surface of the liver is often smooth, with gray and grayish-white nodules and spots ranging in size from a small grain to a nut or more. On the section of the liver, sebaceous foci are isolated.

Histological changes are characterized by the following: the Fabrician bag changes earlier than other organs. The tissue pattern of the follicles disappears. Affected follicles almost completely replace physiologically normal tissue. The liver has a mesh structure. The hepatic tissue strands form a wide-loop network. In the gaps between the parted beams, accumulations of lymphoid cells are detected - small, for example, lymphocytes, and large, lymphoblast-like.

In myeloid leukemia, the liver is enlarged, its surface is smooth, rarely bumpy, brown-red, gray-red and gray-brown in color, with numerous small grayish-white foci or nodules of various sizes. The consistency of the organ is flabby. The spleen and kidneys are also enlarged and riddled with similar lesions or nodules. The bone marrow is watery, light red in color. Tumor lesions can be in other organs. In myeloblastosis, as a rule, the thymus and the bursa of Fabricius are not affected.

Histological examination reveals an excessive accumulation of monocyte-like cells - myeloblasts in the intersinus spaces and in the lumen of the dilated sinuses of the bone marrow. The accumulation of myeloblasts and in a smaller number of promyelocytes is noted in the liver in the intralobular capillaries and around the vessels of the interlobular connective tissue. Quite often reveal extensive infiltrates from the specified cells. The liver parenchyma is atrophied to varying degrees. In the spleen, the sinuses of the red pulp are parted and atrophied due to the growth of myeloblasts and promyelocytes. The follicles are reduced in size, a narrow rim of lymphoid elements is found around the central arteries, or the Malpighian bodies completely disappear.

Similar proliferates from myeloblasts are also found in other organs, the parenchyma of which is to some extent replaced by newly formed cells. Silver impregnation reveals a network of argyrophilic fibers in the infiltrates.

With reticuloendotheliosis, an autopsy establishes a sharp increase in the liver, spleen, kidneys, and bursa of Fabricius. The liver with reticuloendothelial leukemia can be enlarged several times. Its capsule is tuberous, in the places where dense tubercles are located, tumor tissue will be dug. On the section, the foci are dense, gray-brown in color. The spleen is enlarged 4-5 times, moderately dense, less often flabby, the cut surface is smooth, the pulp is reddish-gray. The kidneys, depending on the degree and nature of the proliferative processes, are light brown or gray, with a granular-tuberous capsule, flabby. The bursa of Fabricius is moderately enlarged, focal and diffuse infiltrates from hemocytoblasts are revealed. The main morphological sign of reticuloendotheliosis is excessive proliferation of RES in various organs without their differentiation towards mature blood cells.

589Histological changes are characterized by proliferation of polymorphic histiomonocytic and reticular cells. Cells are found not only in the parenchyma of a number of organs, but also in the adventitia of the vascular walls.

With a proliferative variety of erythroblastosis, a picture of ascites with a gelatinous effusion is often observed, sometimes small subserous hemorrhages occur. The liver is greatly enlarged, reddish-cyanotic or yellowish-red, sometimes pierced by small grayish-white foci. The spleen is enlarged, cherry-red or brown-pink; kidneys swollen, flabby. The bone marrow is cherry red.

With an anemic variety of erythroid leukemia, swelling and anemicity of the spleen, liver and kidneys are characteristic. The bone marrow is liquefied and pale.

Histomorphological studies in the bone marrow reveal pronounced hyperplasia of the sinus (erythropoietic) tissue, which consists mainly of hemocytoblasts, erythroblasts, basophilic normoblasts, polychromatophilic and mature erythrocytes are found in a smaller amount. Intersinus tissue in a state of atrophy. It shows only small accumulations of granulocytes and lymphocytes. In the liver, the intralobular capillaries are dilated and filled with immature cells of the erythroid series, among which there are also immature leukocytes. Hepatic beams in varying degrees of atrophy. In the interlobular connective tissue, around individual vessels, there are small foci consisting of myeloblasts, myelocytes and lymphoid cells. In the spleen, the sinuses of the red pulp are dilated and filled with large immature cells of the erythroid series, among which there are also mature erythrocytes. White pulp in a state of atrophy. In the kidneys, the intertubular capillaries are dilated and filled with immature erythrocytes.

With an anemic variety of erythroid leukemia, anaplastic changes are noted in the bone marrow, and no special deviations are observed in other organs. Erythroid leukemia often occurs in combination with myeloblastosis and hemocytoblastosis.

Diagnosis and differential diagnosis. The diagnosis is established according to the results of epizootological, clinical and pathoanatomical studies, taking into account the results of laboratory diagnostics.

To isolate viruses, tumor nodes are taken from a fallen or forcedly killed bird. The material must be fresh. The same material is used for setting RSK, KOFAL-test and other immunoserological reactions.

Leukemia viruses are detected and identified using the RIF test. Indication of viral leukemic antigen is carried out in the RSK and KOFAL test in the study of blood serum, egg protein, vaginal-but-cloacal material and supernatant from the homogenate of chicken embryos.

Latent leukemia viruses are also detected using the non-producing cell method. The following tests are used: radioimmunoassay, ELISA, phenotypic mixing test (FS), reverse transcriptase reaction.

In terms of sensitivity, the first place is occupied by RIA, the second and third - by ELISA and FS, the fourth - by the study of vaginal cloacal material in CSC, the fifth - by the study of embryo extracts in CSC and COFAL-

590 test, sixth place - isolation of a specific antigen and protein by the CSC method.

In differential diagnosis, Marek's disease, coligranulomatosis, mycotoxicosis, toxic liver dystrophy should be excluded.

Immunity, specific prophylaxis. Chickens that have had a disease caused by one type of virus acquire non-sterile immunity, but are susceptible to other types of virus. A vaccine has been proposed for the specific prevention of erythroblastosis and lymphomatosis, but it has not found wide application.

Prevention. Prevention of the disease is reduced to the implementation of sanitary rules for the maintenance of poultry, isolation of reared young animals from adult livestock on a separate site; the use of vaccines against other avian diseases obtained on chicken embryos from SPF farms.

For the prevention of avian leukemia, vitamins A, E, selenium and cobalt preparations should be included in the diet. It is necessary to constantly fight against blood-sucking insects (bugs, ticks), after replacing the bird, apply insecticidal preparations.

Treatment. Not developed.

Control measures. If leukemia is suspected in birds, the extent of disease coverage in the flock should be determined. To do this, at least 5% of chickens are examined by a serological method. In case of a mass disease, it is forbidden to use hatching eggs to obtain daily young.

All dysfunctional birds are killed and a thorough veterinary and sanitary examination of the meat is carried out.

In the presence of pathological changes in the internal organs, subcutaneous tissue, meat, the carcass is discarded and disposed of, if only the internal organs are affected, they are removed, the carcasses are boiled. In the presence of tumors in the skin or muscles, the carcasses are sent for disposal. Down, feathers obtained from poultry during slaughter are disinfected with formaldehyde vapor.

Control questions and tasks. 1. Give a classification of different types of leukemia in birds. 2. Tell us about Rous sarcoma, erythroleukemia. 3. What does the SPF poultry management system mean? 4. Name the principles of differential diagnosis of neoplastic tumors. 5. List measures for the prevention and control of leukemia.

A viral disease characterized by neoplastic tumors, damage to the hematopoietic system in the form of proliferation of immature hematopoietic and reticular cells of the vascular endothelium. Chickens, guinea fowls, turkeys, pheasants, pigeons, parrots, canaries, finches, quails and birds of other species are susceptible to leukemia. Outbred birds are less susceptible to leukemia.

Pathogen- RNA-containing oncornavirus. The virus is found in the blood, secretions and excretions of birds with leukemia.

The resistance of avian leukemia virus has been little studied; at a temperature of -70°C remains active for 30 days. However, there is no doubt that high temperature neutralizes the virus.

Pre-mortem diagnostics. Initial signs for most forms of leukemia are subtle and uncharacteristic. In chickens, appetite decreases, emaciation develops, the comb becomes pale and wrinkled, and digestion is upset. With damage to the liver and intestines, dropsy of the abdominal organs often occurs.

On palpation of the internal organs of a sick bird, an enlarged liver, nodes of the mesentery and intestines are found behind the end of the keel bone.

The osteopetrifying form is easily recognized at the beginning of the disease by thickening of the bones of the epiphyses and diaphyses, and later on in almost all parts of the bone.

Erythroblastosis and granuloblastosis are clinically difficult to recognize.

Post mortem diagnostics. According to pathogenesis, macro- and microscopic changes, there are three main forms of leukemia: lymphoid, myeloid and erythroleukemia (erythroblastosis).

Lymphoid leukemia characterized by exhaustion, fading of the feather, low mobility of the bird. In a sick bird, a depressed state, paleness of the earrings, and lowering of the back of the body (abdominal dropsy) are observed. In this case, the bird takes the pose of a penguin. On palpation of the bird's body, solid nodes of neoplasms are palpated; the liver is markedly enlarged and protrudes beyond the edges of the ribs. Often, such chickens have a liver rupture during the life of a bird.

At autopsy, a strongly enlarged liver is found compacted or friable. On the surface of the liver and in its parenchyma, nodules or diffuse proliferation of tumor-like tissue of a light gray color are found, giving the organ a tuberosity and a mosaic appearance. The spleen is sharply enlarged up to 60 g and more, red-gray in color, similar to adipose tissue in the cut. The ovary is enlarged, on its surface tuberous growths of tumor-like tissue are visible, like cauliflower, dense texture, gray-white. On the serous integument, multiple growths of tumor-like tissue are sometimes found. Histological (cytological) examination of the affected areas of the liver, spleen, kidneys, ovary and mesentery finds an abundant accumulation of lymphoid cells, characterized by basophilic staining of the protoplasm and the presence in the center of a large round nucleus, poor in chromatin. At the same time, there is a loss (atrophy) of the cells of these organs.

myeloid leukemia(granuloblastosis) is characterized by excessive reproduction and accumulation of immature myelocytes due to the action of the leukomoid factor on bone marrow function (in the bones of the chest and pelvis). Although this type of leukemia is rare, it proceeds malignantly, chickens die on the 8-10th day from the moment they develop leukemia.

When carcasses (corpses) are opened, a strong enlargement of the liver, spleen, and kidneys is found. They are pale red-gray in color, flabby. In these organs, as well as in the muscle of the heart, in the thymus gland, on the serous membranes and mesentery, tumor-like formations are found. Bone marrow gray-red color, colloidal consistency. In parenchymal organs, histological examination reveals scattered multiplication of basophilic myelocytes - tumor-like growths of cells in organs. Myelocytomas are more common in flat bones.

erythroleukemia(erythroblastosis) is relatively rare in chickens and turkeys. It takes 6-7 days and ends with death. During life, erythroleukemic birds show icteric coloration of the crest, earrings, skin, diarrhea, exhaustion and exhaustion; the blood of patients is watery, slowly coagulates, the number of erythroblasts in it is increased.

Examination of dead birds reveals emaciation and cyanosis of carcasses, banded spotted hemorrhages under the serous membranes of parenchymal organs and on the intestinal mucosa. The liver is greatly enlarged, light brown in color, flabby, ruptures are often observed. The spleen is also enlarged, light purple in color, its pulp is red, flabby, prone to tearing. The kidneys are light brown, enlarged. The brain of the sternum is semi-liquid, gray-red.

Leukemic lesions must be differentiated from avian tuberculosis. It should be remembered that with tuberculosis, the foci in the liver, spleen, in the walls of the intestines and the mesentery are bumpy, very dense, calcifications are noticeable on the cut, which does not happen with leukemia. Pullorosis is characterized by a pronounced inflammation of the ovary, the formation of pullor abscesses, seropurulent inflammation of the serous integuments and vitelline peritonitis, which does not happen with leukemia.

To clarify the type of leukemia, a cytological examination should be carried out. To do this, smears are prepared from the affected foci of parenchymal organs. Separate forms of leukemia are differentiated according to the nature of cell clusters observed in the affected organs.

At

in the absence of anemia, or jaundice, or pathological changes in the muscles, or with limited damage to internal organs, they are disposed of, and the carcass is boiled or processed into canned food. In case of a generalized process, or damage to the skin and muscles, or in the presence of exhaustion, jaundice carcasses with organs are disposed of regardless of the degree of damage.

ORNITOSIS (PSITTACOSIS)

Respiratory disease of poultry, characterized by a predominant lesion of internal organs, mucous membranes of the upper respiratory tract, conjunctiva and manifested by catarrhal-purulent rhinitis, conjunctivitis and diarrhea. Domestic and wild birds are susceptible to the disease. In humans, the disease manifests itself in the form of a typical respiratory infection.

Pathogen- Chlamydophila psitta-ci. These are immobile coccoid "microorganisms. The resistance of C. psittaci in the external environment is low; the pathogen is destroyed especially quickly during decay, at 60 ° C - within 10 minutes. In a dry state, it lasts up to 5 weeks, at room temperature and sunlight - up to 6 days, in water - 17 days, in bird droppings - 4 months or more.

Pre-mortem diagnostics. Patients show drowsiness, weakness, loss of appetite and diarrhea. In the future, muscle tremor develops.

Ducks, turkeys, and geese develop weakness, diarrhea, keratitis, conjunctivitis, pneumonia, and cachexia. Adult chickens usually get sick subclinically. In an acute course, patients develop diarrhea, anorexia, salivation, conjunctivitis. Chickens may have muscle tremors. impaired coordination of movement and other signs of meningoencephalitis.

The intestinal mucosa is diffusely colored in intense pink color, multiple necrotic foci are found on it. In the lungs, foci of compaction are found -

In the chronic course of ornithosis, there are no noticeable changes, and if they occur, they look like salmonella lesions. Observe desquamation of the epithelium of the intestinal mucosa-

Histological examination in the liver and spleen reveals a sharply protruding mononuclear infiltration, the presence of hemosiderin and elementary bodies; in some cases, cell necrosis is found.

Veterinary-sanitary assessment. Boil the carcasses VSHCHOt ^ internal organs are disposed of. Down and feathers are destroyed.

ADENOMATOSIS OF THE LUNG

A chronic, long-term viral disease of sheep, cattle £> horses and dogs, characterized by progressive metaplasia of the bronchial and alveolar epithelium, growth in the lungs of glandular tumors that become malignant. A person also becomes ill with adenomatosis of the lungs.

Pathogen- filterable virus.

Pre-mortem diagnostics. Clinically, the disease manifests itself in the last stages and is accompanied by severe shortness of breath, which is especially noticeable during the transfer of animals.

Post-mortem diagnostics. The mucous membrane of the larynx and trachea is swollen and cyanotic. In the lungs, limited or diffuse foci of dense consistency, grayish-white or grayish-pink color are found. From the surface, the lesions seem to be slightly sunken. When the lungs are cut, a clear foamy liquid flows down from the small and large bronchi, sometimes in the form of viscous mucus. Bronchial and mediastinal lymph nodes are enlarged, dense to the touch, muddy lymph is released from the surface of their incision.

Differential diagnosis. When differentiating adenomatosis and similar diseases, it is necessary to exclude verminous pneumonia of dictyocaulous origin, atelectasis of the lungs (usually apices), resulting from lung inactivity in the postnatal period, catarrhal and other pneumonias resulting from secondary infection (ornithosis, salmonellosis, chronic pasteurellosis ).

Veterinary and sanitary assessment. When adenomatosis of the lungs is established, the release of meat and other raw products is prohibited.

The carcasses of emaciated animals, together with their heads and internal organs, are sent to the production of meat and bone meal, which is then fed only to poultry.

Carcasses and internal organs without visible pathological changes, obtained from the slaughter of sick and virus-positive animals, are sent for the manufacture of boiled and cooked-smoked sausages, for meat loaves or canned food.

The head, bones, lungs and other pathologically altered organs, as well as the gastrointestinal tract, are sent for disposal. The skin and wool are disinfected.

Similar information.

Avian leukemia is a viral disease characterized by the formation of malignant tumors of the hematopoietic system.

Also, avian leukemia is most often characterized by a chronic course and nonspecific clinical signs. The disease was first described at the end of the 19th century, and the causative agent of the disease was isolated in the middle of the last century. At the moment, avian leukemia is common in all countries with industrial poultry farming and causes serious economic damage to the industry.

Etiology

The cause of avian leukemia is a virus belonging to the retrovirus family. This family includes seven genera and a huge number of viruses pathogenic for birds, various animals and humans. Most of the representatives of the family of retroviruses are characterized by a pronounced tropism for the cells of the hematopoietic and lymphoreticular system. In addition to the defeat of these systems, infection with retroviruses leads to immunosuppression and the inability of the body to give an adequate response to the introduction of pathogens.

It is the representatives of the Retroviridae family that are responsible for the development of such severe, deadly diseases as:

Human Acquired Immunodeficiency Syndrome;
. bovine leukemia;
. feline leukemia and others.

The avian leukemia virus, like all members of the retrovirus family, is characterized by relatively low resistance in the external environment. Outside the body, the virus dies quickly enough, the action of elevated temperatures also inactivates the virus: at a temperature of +60 ° C, the pathogen dies within one and a half to two hours, with boiling for 5 minutes. Most of the disinfectants in the accepted concentration have a detrimental effect on the virus; under the action of ultraviolet light, retroviruses die within 45-60 minutes.

At the same time, lyophilization and freezing allow the causative agent of avian leukemia to remain viable for a long time. Thus, during experimental drying, the viruses remain alive for at least 9 years.

epizootology

Most poultry and wild birds are susceptible to the leukemia virus, but most often the disease is recorded in chickens. As a rule, a bird falls ill at the age of six months to a year, however, the development of the disease in younger age groups is not excluded, for example, in chickens aged 2-4 months.

Since the virus affects almost all organs of the bird, and is also found in the blood of a sick bird, its release into the external environment occurs with droppings, nasal expiration, and also with eggs. It was noted that the virus in the body of a bird can be in a dormant state for a long time, leading to the development of the disease against the background of violations of the conditions of keeping and feeding, hypothermia, overcrowding of livestock, gas contamination of poultry premises and other stress factors.
It has been established that some breeds of chickens have a high genetic predisposition to the development of leukemia in them. In particular, such breeds include the Leggorn and the Rhode Island. Most often, leukemia is observed in the form of sporadic foci, but in some cases enzootic outbreaks are possible. With the spread of the leukemia virus among susceptible livestock, more than 70% of the incidence of all birds in the herd is noted.

Pathogenesis

The pathogenesis of avian leukemia is not well understood. It is believed that after penetration into the body of a bird by the alimentary or aerogenic route, the virus spreads with blood flow through various tissues and organs, among which the main ones are the organs of the reticuloendothelial system, settles in them and, if adverse factors affect the body, exhibits a pathogenetic effect. Unlike the development of malignant tumors, generalization of leukemia does not occur by metastasis, but due to the emergence of new foci of the pathological process.

Course and symptoms

The incubation period for poultry leukemia can range from several days to months. First of all, the development of clinical signs of leukemia is associated with the resistance of the organism and the amount of the pathogen that has entered the bloodstream. A feature characteristic of leukemia is a long subclinical course of the disease and a rather short clinical stage, ending in death.

There are several forms of the disease in connection with the characteristics of the course. The most common is the lymphoid form, also called lymphomatosis. Also, in descending order, note:

reticuloendotheliosis;
. myeloid form of leukemia;
. erythroblastosis.

With lymphomatosis, nodular or diffuse lesions of internal organs, a decrease in hemoglobin levels, weakness, a sharp (up to 30%) decrease in the number of erythrocytes with a significant (2-4 times) increase in the number of white blood cells are noted.

Reticuloendotheliosis is characterized by a predominant lesion of endothelial and reticular cells of the lymph nodes, bone marrow, liver and spleen, as well as connective tissue macrophages with the formation of malignant tumors in these organs. Observe lymphopenia, chest dropsy, enlargement of the liver and spleen.

In myeloid leukemia, the hematopoietic tissue of the red bone marrow is predominantly affected with the formation and release into the bloodstream of a large number of altered white blood cells. This form of the disease leads to suppression of the production of erythrocytes, normal leukocytes and platelets, which entails systemic dysfunctions of all organs and the body as a whole. It occurs in leukemic and aleukemic forms. At the same time, in a sick bird, the formation of small dense neoplasms on various parts of the body, poor blood clotting and its light red color are often observed.

With erythroblastosis, immature erythrocytes (erythroblasts), as well as red blood cells that have abnormalities, are released into the bloodstream. Erythroblastosis is the rarest form of leukemia in poultry, often acute, quickly leading to death against the background of general exhaustion.

Symptoms for all forms of avian leukemia do not have specific signs. Note:

• weakness;
• shortness of breath
• decrease in productivity;
• emaciation;
• blue earrings and comb.

Most often, leukemia is suspected during a post-mortem autopsy of dead birds and the detection of neoplasms and hemorrhages in various organs and tissues against the background of general exhaustion.
As a rule, making a diagnosis of leukemia in poultry on the basis of unclear clinical signs and autopsy results can be quite problematic. If this disease is suspected, it is necessary to conduct a thorough laboratory diagnosis, including detection of the virus in the pathological material and its subsequent identification in immunofluorescence and complement fixation reactions, enzyme immunoassay, KOFAL test, and others.

Control measures and prevention

At the moment, no effective treatment for avian leukemia has been found. There are also no methods of specific prevention due to the poor knowledge of immunity in case of illness. The basis for preventing the occurrence of leukemia in a poultry farm is to prevent the introduction of infection from outside (importation of hatching eggs and young animals only from farms that are free from leukemia), separate rearing of poultry intended for slaughter for meat using the "empty-busy" principle, strict observance of veterinary and sanitary livestock keeping and feeding standards. In addition, periodic clinical examinations of poultry, a thorough pathoanatomical autopsy, especially depleted individuals, systematic disinfection of poultry premises after their release and mechanical cleaning are mandatory.

Equally important is the optimization of the poultry diet with the mandatory introduction of vitamins A and E, cobalt and selenium preparations into it, as well as. Preventive measures include any actions aimed at increasing the resistance of the bird's body.

Promising in relation to the fight against avian leukemia is breeding work, which aims to create disease-resistant breeds and crosses, as well as the creation of herds free from the virus-causative agent of the disease.