Syndrome of decreased egg production of chickens, egg casting syndrome, EDS-76, "Syndrome-76", chicken adenovirus disease(Egg drop syndrome - eng.) - a viral disease that affects commercial and breeder laying hens, characterized by a decrease in egg production, softening or disappearance of the egg shell, loss of shell color in breeds of hens that lay brown eggs.

Prevalence... The disease was first described by Van Eck in 1976. It is currently reported in Holland, England, Northern Ireland, France, Italy, Germany, Spain, Belgium, Yugoslavia, Denmark, Hungary, Sweden, Argentina and the United States.

Economic damage caused by the disease is due to losses associated with a decrease in egg production. According to J. Macpherson, the loss in England was £ 2.4 million a year. French scientists note that in birds in cages, productivity is restored within 4-6 weeks, and when kept on the floor, it is 8-10% lower. Egg loss per poultry in disadvantaged flocks is 17.7%, estimated at 116.9p. A sick bird carries up to 15% of deformed, with a weak or no shell or depigmented eggs. According to Darbyshire (1980), the number of eggs with damaged shells can reach 38-40%. J. McFerran et al. (1978) note that the loss of productivity in this disease is on average 12 eggs per hen.

Economic damage is also associated with a decrease in the quality of hatching eggs. More than 50 eggs from a laying hen are not suitable for incubation due to the fragility of the shell. In addition to high culling, there was also a decrease in hatchability and viability of chicks in the first days of life.

Causative agent... Various researchers have identified several strains, the identity of which has been confirmed by serological studies. Strain 127 was isolated in Northern Ireland from the mucous membrane of the nasal cavity and pharynx of birds. The virus (ВС 14) was isolated from blood leukocytes, its identity was serologically confirmed to the virus 127 isolated from oviducts, feces, nasopharynx of chickens in affected herds; antibodies to this agent were also found (W. Baxendale, 1977, 1978; J. McFerran et al. , 1977, 1978). Under experimental conditions, the disease was reproduced by infection of laying hens and broilers, and it was established that an isolated virus is an etiological agent (W. Baxendale, 1977; W. Baxendale et al., 1978; McCraken, J. McFerran, 1978).

Strain D61 was isolated from the cloaca of a laying hen in England. In Hungary, strain B 8/78, identical to strain 127, was obtained; in France, 3 strains were isolated. The virus was identified as an adenovirus (Todd, McNulty, 1978), but group-specific antigens with the main avian adenoviruses by gel diffusion have not been established (W. Ba-xendale, 1977; J. McFerran et al., 1978). However, some degree of cross-reactions with avian adenoviruses was observed using the method of indirect immunofluorescence (W. Baxendale, 1978).

The egg-laying virus is not associated with any of the 11 serotypes of avian adenoviruses (J. McFerran et al., 1978) and differs from other avian adenoviruses in the ability to agglutinate erythrocytes of chickens (J. McFerran et al., 1977), ducks and geese (W. Baxendale, 1977).

The EDS-76 virus multiplies in high titers in duck kidneys, duck embryo liver and duck embryo fibroblasts, worse - in chicken liver cells and extremely low in chicken embryo fibroblasts. The virus is not cultured in mammalian cells. It replicates in the nucleus of cells in the manner described for the first subgroup of adenoviruses. An electron microscopic study of thin sections of infected cells revealed viral particles and associated inclusion bodies in both human-type adenoviruses and avian adenoviruses.

The pathogen is resistant to ether and pH over a wide range. Its infectious properties are lost within 30 minutes at 60 ° C, it is also inactivated by trypsin, urea and pyridine. This is a DNA-containing virus that does not have an outer shell, the density in cesium chloride is 1.34; the sedimentation constant in sucrose is 940; the diameter of the virion is 75-80 nm, the symmetry of the capsid is cubic.

V. Kraft et al. (1979) electron microscopic examination of isolate 127. 3 lines were observed in the CsCl gradient. Two lines had a density of 1.32 g / ml, which were not separated by fractionation and were responsible for high hemagglutinating activity and infectivity. These lines contained particles morphologically typical of adenoviruses. The third line (density 1.30 g / ml) consisted mainly of broken particles and showed a noticeable peak in hemagglutinating activity.
Hemagglutinin of the virus is stable for 30 min at 70 ° C, but higher temperatures cause inhibition of activity. Purified soluble hemagglutinin contains 2 polypeptides with molecular weights of 65,000 and 67,000, consists of rod-shaped structures 25-30 nm in length.

The virus is icosahedral, particle size, capsid structure, and the number of capsomeres are typical for adenoviruses (V. Kraft et al., 1979).

Epizootological data insufficiently studied. Egg loss syndrome affects laying hens of all breeds between 25 and 35 weeks of age. The most susceptible beef breeds that give brown eggs, as well as breeding birds. Breeds that lay white eggs are less susceptible. The duck-casting syndrome virus is suspected to be of duck origin, but it is non-pathogenic to them. In Northern Ireland, chickens are believed to have become infected following the use of the Marek's disease vaccine from the Rispen strain obtained from duck tissue culture in the Netherlands. In Ireland and the Federal Republic of Germany, a disease with signs of EDS-76 was observed for the first time in chickens imported from the Netherlands.

The disease is reproduced by artificial infection of poultry conjunctivally and orally. The virus spreads vertically through the egg. A number of researchers also recognize the horizontal route of transmission, attaching great importance to droppings. The spread of the virus is suspected with the semen of the roosters.

Epizootological feature of the egg production syndrome- the ability of the virus not to manifest itself in the body of birds until they reach sexual maturity. The reason for the activation of the pathogen is the stressful effect on the body, due to the onset of oviposition.

Pathogenesis insufficiently studied. It is only known that there is a violation of the mechanism of formation of the eggshell. Ovarian atrophy and hemorrhage are also observed. Acidity increases in the uterus, which can lead to calcium dissolution and impaired shell formation. In case of experimental infection of laying hens, defective eggs appear on the 4th-7th day, the content of protein and calcium in the blood does not change.

Clinical signs are usually not present. However, ruffled feathers, anemia, diarrhea, a state of prostration, and decreased activity during oviposition can be observed. In the later stages of the disease, cyanosis of catkins and scallops may appear in 10-70% of birds. Typical signs of the disease: discoloration of the shell in eggs with a brown color, the appearance of eggs with a thin shell or without it, a decrease in egg production. These signs persist from 2-3 to 6-12 weeks and are typical for meat breeds and brown crosses. For chickens of egg breeds, a change in the internal quality of eggs is also characteristic: the white becomes watery and cloudy.

Pathological changes or absent, or there is a weak catarrhal enteritis, atrophy, edema and mononuclear infiltration of cells of the glandular tissue of the uterus and oviducts.

Diagnosis and differential diagnosis... The diagnosis is based on data of clinical signs, pathological changes and serological examination. The most reliable diagnostic method is the hemagglutination inhibition reaction (RTGA). In the study of paired sera 15 days and 2-3 weeks after infection, an increase in the titer of antihemagglutinins to 1: 1280-1: 2560 is noted.

The egg casting syndrome must be differentiated from Newcastle disease, infectious bronchitis, coccidiosis, helminthiasis, poisoning with pesticides, fungicides, mycotoxins and various factors of non-infectious etiology that cause a decrease in egg production (housing conditions, feed quality, diet balance, etc.).

Treatment not developed. To maintain the optimal level of hatchability and viability of the offspring, it is recommended to use complete diets, especially in relation to essential amino acids, vitamins and microelements.

Immunity and specific prophylaxis... A naturally recovered bird develops a tense immunity. 7 days after infection, virus neutralizing, antihemagglutinating and precipitating antibodies associated with IgG immunoglobulin are found. Chicks hatched from infected chickens retain their maternal antibodies, which have a half-life of 3 days. Passive antibodies ensure the resistance of chickens to infection in the first 4 weeks of life.

For specific prophylaxis, an oil formol vaccine is used from the BC 14 strain grown on a duck embryo cell culture. The vaccine is administered once intramuscularly or subcutaneously at a dose of 0.5 ml (1000 HAU), starting from 18 weeks of age.

The EDS-76 vaccine was tested in France, the Netherlands, Great Britain, Belgium and Luxembourg, Argentina. After vaccination, the viremia phase and associated virus excretion are not observed, egg production and shell quality are improved. Immunity is formed after 15 days, maximum antihemagglutinins accumulate after 30 days. The antibody titer begins to decline 12-16 weeks after vaccination. Antibodies are not detected after 40-50 weeks.

Vaccination is considered as a temporary measure due to the danger of the spread of the virus and its adaptation to chickens. In Yugoslavia (M. Krecov et al., 1980), a vaccine inactivated with 13-propiolactone and adsorbed with aluminum hydroxide, made from the virus of strain 127, was tested with a positive result.

Prevention and control measures... For incubation, it is recommended to use eggs from hens over 40 weeks of age, giving negative results in serological tests. In England, Northern Ireland and the Federal Republic of Germany, the slaughter of poultry that reacts positively in serological reactions in order to prevent the vertical transmission of the pathogen through the egg is considered a radical measure to combat and prevent egg production syndrome. An inactivated vaccine is allowed.

Adenovirus infections - diseases of birds of different species (chickens, turkeys, guinea fowls, pheasants, muscovy ducks, pigeons, quails, budgerigars). They are caused by 12 types of avian adenoviruses that do not share a common antigen group with other adenoviruses in humans, monkeys, pigs and mice.

Avian adenoviruses belong to the adenovirus family, since they share a number of common properties with this family: particle size, virion structure, genome structure, type of replication. In adenoviruses, the virion is devoid of the outer lipoprotein membrane, does not contain lipids and glycoproteins, has a spherical capsid shape, 70-80 nm in size.

Adenoviral infections in birds include: CELO - infection, EDS-76 - egg-loss syndrome, adenoviral respiratory disease, hepatitis with inclusion bodies.

Egg Drop Syndrome- a disease of laying hens, characterized by softening, absence (casting) or depigmentation of the egg shell. It is accompanied by a significant decrease in egg production.

The disease was first described in Holland in 1976 by J. Van Ecke et al. The studies carried out allowed us to exclude NB, ILT of birds. Before him, no one in the world paid attention to the characteristic dynamics of a decrease in egg productivity. Antibodies to the EDS-76 virus were also not detected in any museum blood serum sample obtained from chickens before 1976. This is an indisputable confirmation that the onset of the disease is timed to a certain period.

At various times in a number of countries strains of the EDS-76 virus were isolated: BC-14 - in Great Britain, B / 78 - in Hungary, E-77 - Italy, 3877 - France, J RA-1 - In Japan. All obtained isolates were serologically completely identical to the first isolated strain -127.

STYA-76 is widespread in countries with highly developed technology of industrial poultry farming and causes very significant economic damage, especially in breeding farms. Losses are due to lost eggs from layers during the peak of laying (according to some data - up to 15 eggs per layer, according to others - up to 25%, in the USA - the damage reached $ 5 million), as well as from a decrease in the commercial quality of commercial eggs and from breeding hens (culling was up to 50 eggs per head). As a rule, in those who have been ill, egg production is not restored to its original level. Currently, the disease has been sufficiently studied, however, the issues of etiology, epizootology, pathogenesis are largely controversial.

Causative agent- DNA-containing virus of the adenovirus family. It was isolated in 1976 in Northern Ireland from the nasal cloacal drainage and ovaries of sick birds - now this strain is known under number 127, and identified as the causative agent of EDS - 76.

There is an opinion of a number of scientists that the EDS-76 virus is a duck adenovirus that does not cause pathology in natural "hosts". The disease first appeared in Holland, a country of intensive duck farming. The primary infection of chickens with it was made artificially, with the introduction of a vaccine against Marek's disease from the Rispens strain, prepared using a culture of fibroblast cells of duck embryos contaminated with adenovirus. The virus quickly adapted to a new "host" - chickens and showed its pathogenic properties.

The characteristics of the EDS-76 causative agent fully correspond to the characteristics of other avian adenoviruses, with the exception of its ability to agglutinate the erythrocytes of chickens, ducks and geese. On this basis, it is even more "avian adenovirus" than other adenoviruses that do not have a hemagglutinating ability.

The virus is unstable to heat: a temperature of + 65C completely inactivates the virus in 30 minutes. The EDS virus is 15 times more sensitive to UVL radiation than the infectious bronchitis virus. The EDS-76 virus is resistant to changes in the pH of the medium, especially in an alkaline medium. Resistant to repeated freezing and thawing, to the effects of other physical factors, as well as to disinfectants.

Epizootology. Most often, EDS-76 affects laying hens of all breeds with the maximum manifestation of the disease during the period of increased egg-laying at the age of 26-35 weeks of age. Poultry of meat breeds is especially susceptible.

It was noted that birds over 40 weeks of age do not suffer from EDS-76 and the virus does not secrete, but the blood contains antibodies to this virus.

Adenoviruses are also widespread among domestic and wild ducks, which at the same time do not get sick. Antibodies have been detected in 85% of the ducks and 65-100% of the geese in Hungary. In natural and wild conditions, they are a reservoir of the pathogen in nature. Despite the low contagiousness of the disease, there is a danger of introduction of the pathogen into the territory of the economy by wild birds: pigeons, sparrows.

The main source of the EDS-76 causative agent is sick chickens that excrete the virus with feces or pass it on to their offspring with an egg.

The main route of spread of adenoviruses is vertical. The horizontal and contact path of transmission of the pathogen is of lesser importance. The disease spreads more quickly when chickens are kept outside.

An epizootic feature of the disease is a strictly defined time of reactivation of the pathogen after the contaminated bird reaches full sexual maturity. The reason for this may be stress, which is the physiological restructuring of the body of laying hens before the start of the active stage of oviposition. Other specific predisposing factors for the onset of the disease, except for age, have not been established.

Pathogenesis. During the period of latent infection, the virus persists in the intestine. The reactivation of the virus occurs due to a change in the hormonal profile at the beginning of oviposition, which is considered a stress factor. Apparently, the virus has a direct effect on the glandular epithelium of the uterus, which causes the clutch of shellless or thin-shelled eggs.

Clinical signs... No typical symptoms of EDS-76 were noted. The bird has a reduced appetite, tousled plumage, diarrhea. The bird lays depigmented, deformed and defective eggs within 2-3 weeks. The amount of "marble" eggs increases significantly, the percentage of broken and notched eggs increases. The white of the egg is watery and cloudy.

Egg productivity decreases on average by 15-30%, in some cases - up to 50%. The decrease in productivity increases gradually over 5-6 weeks, after which the productivity is very slowly restored when the chicken is kept in cages, and does not recover when it is on the floor.

The mortality of birds at EDS-76 is insignificant even at the peak of the disease. Mortality among layers is up to 3-5%, mainly due to yolk peritonitis, pecking.

When embryos are damaged by the virus, their death begins 4-6 days after infection and continues until the chicks hatch.

Pathological changes are localized mainly in the organs of the reproductive tract and are expressed in the form of ovarian atrophy, sometimes hemorrhages are found in them. In all cases, a small number of maturing and mature follicles in the ovary are noted. The oviduct, as a rule, is shortened, its wall is thinned, with foci of hyperemia. The liver may be enlarged, edematous, and flabby.

Diagnostics. A preliminary diagnosis is made on the basis of a comprehensive assessment of the data from an epizootic survey of a poultry farm. At the same time, special attention is paid to the dynamics of egg production in adult chickens, the mass death of day-old chickens. The age of birds during the decline in egg production is of great diagnostic value.

During a histological examination of the affected areas of the oviduct, intranuclear bodies are found - inclusions in epithelial cells.

Laboratory diagnostics is based on the isolation of the virus from pathological material (preferably on duck embryos) and its identification in the RZGA, MFA.

Serological diagnostics (RSHA, RDP, ELISA) are used to detect antibodies to the EDS-76 virus in birds in paired blood sera in dynamics, as well as to establish the strength of immunity.

In the differential diagnosis of EDS-76, a decrease in egg production caused by CELO viruses, infectious bronchitis, Newcastle disease or a violation of conditions of detention is excluded.

Prevention and control measures. In a point unfavorable for EDS, it is imperative to strictly observe veterinary and sanitary measures to exclude the spread of the pathogen from the focus of infection. Sanitize the supply and exhaust ventilation system.

A favorable prognosis is possible only with the use of specific prophylaxis. The bird is immunized with a liquid inactivated sorbed vaccine against EDS-76 once intramuscularly at the age of 100-110 days. Monovalent and associated forms of vaccines based on mineral and oil adjuvants (against infectious bronchitis, IBD, Newcastle disease and EDS-76) have been developed and introduced into the practice of poultry farming.

Egg Drop Syndrome-76 (EDS-76)- a viral disease characterized by damage to the reproductive system of chickens, a decrease in egg production, and a deterioration in the quality of eggs.

Damage from EDS-76 is caused by the shortage of up to 10-30 eggs per hen on average (up to 50 eggs are discarded from breeder hens), the laying of shellless eggs, eggs with a blood ring, a decrease in hatchability of chickens and their low viability up to two weeks of age.

Etiology... The causative agent of the disease is a virus from the genus Aviadenovirus, the Adenoviriclae family, identified as a duck adenovirus by some physicochemical and biological properties. The virion has a cubic type of symmetry, lacks a supercapsid shell, has a size of 80 nm in diameter, contains 6 capsomeres on the edge. At the tops of the icosahedron, clavate thickenings can be detected. It is believed that they are carriers of the surface antigen of the virus - hemagglutinin. The genome of the virus is formed by DNA. The molecular weight of the virus is 170-175 megadaltons, the sedimentation constant is 560, the buoyant density in the cesium chloride gradient is 1.32-1.35 g / cm 3. The virus is resistant to ether, chloroform, temperature factors. When the vaccinated material is heated to 56 ° C for 30 minutes, the infectious activity decreases by no more than 50%. Heating to 70 ° C causes a loss of infectious and hemagglutinating activity after 10 minutes. In a frozen state at -25 ° C, the virus remains viable for more than 3 years. The virus is relatively stable at pH 6.0-9.0. In 50% glycerin at a temperature of -30 -50 ° C, the virus contained in the pathological material remains in an active state for several years. The virus is well stored in a lyophilized state. The leading place of localization of the virus in the body of birds is the organs of the reproductive system, but during the period of latent infection, it can persist in the intestines and other organs. The virus can be isolated from the oviduct, leukocytes

blood, upper respiratory tract, nasal and pharengial mucus, liver, contents of the cloaca of sick chickens within 3-5 days from the moment the first clinical signs of the disease appear. In the internal organs and tissues of experimentally infected birds, the virus persists for up to 5 weeks. It can be found in faeces within 2 weeks after infection. Antigenic variants and types of the EDS-76 virus have not been established. In sick chickens, on the 6-8th day after infection, serum antibodies are produced, which have virus-neutralizing, antihemagglutinating and precision properties. There are two peaks in the dynamics of antibody production. The first (JgM peak) is detected on days 10-11, the second (JgG peak) - on days 16-18 after infection. Neutralizing antibodies begin to form on the sixth day after infection, with an increase in titer up to 28 days. Precipitating antibodies are also formed from the 6th day after infection, but from the 17th day, their titer begins to decline. Chicks from seropositive parents up to 4 weeks of age contain maternal antibodies, with a half-life of 3 days. But they cannot permanently protect the bird from adenoviruses transmitted vertically to the offspring and beginning to manifest themselves in stressful situations, including during the period of peak oviposition. The EDS-76 virus does not belong to any of the 12 currently known avian adenovirus serotypes and, unlike them, is capable of agglutinating the erythrocytes of chickens, ducks, turkeys, and geese.

Epizootology... Laying hens of all breeds are susceptible to the disease with the maximum manifestation of the disease during the period of maximum egg production (180-140 days), but the occurrence of the disease is possible at any period of the productive cycle. Chickens of high-yielding meat-egg and egg crosses are more susceptible to the disease. The EDS-76 virus is widespread among domestic and wild ducks, as well as geese, is apathogenic for them and does not cause clinical manifestations of the disease. The persistence of the pathogen is usually confirmed retrospectively by the presence of specific antibodies, but in many cases the virus can be isolated from ducks and geese. After experimental infection of goslings with the EDS-76 virus, the pathogen can be isolated from the feces of infected birds within 3 weeks, which gives reason to consider geese as a potential source of infection. Antibodies to the EDS-76 virus can be found in the blood serum of wild geese, herons, sparrows, swans, owls, storks, however, there is no information on the clinical manifestation of the disease among these bird species. The leading pathway for the spread of the pathogen is transovarian. Eggs are especially intensively infected during the period of viremia, which coincides in time with the decline in egg production. Transmission of the pathogen with the sperm of cocks is not excluded. The horizontal spread of the pathogen is observed at the initial stage of the disease and is most pronounced with the floor keeping of the bird. During this period, the virus is intensively excreted in feces, pharyngeal and tracheal mucus, contaminates feed, the environment, which contributes to the re-infection of the herd by eating infected feed and droppings. An epizootic feature of the disease in some chicken crosses is the unequal degree of manifestation of infection in different poultry houses of an unfavorable economy according to EDS-76. In addition, there were cases when in the same poultry house, along with the affected poultry, a significant number of laying hens remained, maintaining normal egg production throughout the entire productive period.

Clinical signs... There are no characteristic symptoms of the disease. Possible diarrhea, some depression, decreased feed intake. At the peak of the disease - weakened breathing, liquid greenish droppings, noted within 1-2 weeks. In the later stages of the disease, cyanosis of the earrings and crest occurs. The mortality of birds with EDS-76, even at the peak of the acute form of the disease, is insignificant.

In rare cases, among adult layers, it can reach 3-5%, mainly due to yolk peritonitis and cloacitis. The leading symptom of the disease is a decrease in egg production by 15-30%, and in some herds by 50% or more. The decrease in egg production proceeds in a certain pattern: the entire recession period is 6-7 weeks, of which 4-5 weeks fall directly into the recession, and 2-3 subsequent weeks - during the recovery period. With cage keeping, the productivity of chickens is restored almost completely or remains 1-3% lower than the norm, and with floor keeping, as a rule, it is 7-10% less than the egg production that preceded the decline. In the process of recovering from EDS-76, the bird lays shellless ("casting eggs") or depigmented eggs with thinned shells, with annular or banded, rough formations on the surface for 6-8 weeks. The number of "marble" eggs increases significantly, the percentage of eggs broken and notched increases. The incubation qualities of the eggs deteriorate, while their fertility, hatchability and viability of the chicks decrease during the first two weeks of life. Changes in the quality of the shell and the so-called "fatty egg" are most common in colored hens and broilers. In chickens of white crosses, mainly the protein part of the egg is changed in the form of its local liquefaction.

Pathomorphology... Pathological changes in the internal organs of birds with EDS-76 are very weakly expressed. In the acute form, in some cases in the ovary, changes of an atrophic nature, a decrease in the number and size of follicles, hyperemia or hemorrhage in the connective tissue capsule of the follicles, their deformation and degeneration are noted. There are areas of the ovary with completely degenerated follicles and turned into a necrotic mass of yellowish-brown color. The appearance of cysts is possible. The oviduct is generally shorter and thinner than that of healthy birds. Revealed hyperemia and punctate hemorrhages in the mucous membrane, its swelling, most pronounced in the uterine oviduct, less often in the vaginal and protein parts. In some cases, vitelline peritonitis is noted. The liver is sometimes enlarged, flabby and yellowish in color. At the same time, there is an increase in the gallbladder, its overflow with watery bile, light green in color. Information on the damage of the lymphoid organs of birds by the EDS-76 virus is contradictory.

Diagnostics... The diagnosis is made on the basis of epizootological, clinical, pathological data and laboratory results, which include: virus isolation in duck embryos, duck embryo fibroblast cell culture or liver tissue culture of duck or chicken embryos with subsequent identification of the pathogen in RHA, RZGA, MFA , ELISA, bioassay setting on chickens; determination of specific antibodies in blood serum or yolks of laying hens in RZGA or ELISA; histological examination of the organs of the reproductive tract.

For virological research, samples of the ovary with follicles, oviduct, rectum with contents, cloacal washings, blood with an anticoagulant (heparin or 1% sodium citrate solution) are used. Sampling of pathological material is carried out in the first 3-5 days after the onset of the disease and no later than 2 hours after the clinical death or slaughter of the bird. Pieces of organs 1-1.5 cm in size are placed in a test tube or bottle with 5.0-8.0 ml of saline or Hanks solution containing 1000 U of penicillin, 1000 μg of streptomycin and 50 nystatin per ml. As a stabilizer, it is advisable to add 0.5-1% bovine serum albumin or 0.5% gelatin to the solution to prevent inactivation of the virus. Cloacal swabs are taken with a sterile cotton swab and immersed in saline containing the above additives. Blood is usually drawn from the brachial (axillary) vein, jugular vein, or by puncture from the heart. For subsequent studies, a leukocyte fraction is isolated from whole blood. At the same time, 10-15 ml of blood is taken from each bird, before feeding, a few drops of heparin or sodium citrate are added to it, and centrifuged at 1000 rpm. within 30 minutes and then the buffy coat is aspirated with a pipette. The obtained leukocytes are transferred into a sterile saline solution, where they are added at the rate of 100 U of penicillin, 100 μg of streptomycin per 1 ml of solution and subjected to several cycles of freezing and thawing to destroy the cells. A suspension of half-destroyed leukocytes is used to isolate the virus. Before starting the virus isolation procedure, the pathological material should be freed from the preservative, which is achieved by repeatedly washing the samples with fresh portions of sterile saline solution containing 0.15 mol / L sodium chloride and pH 7.0-7.2. Then the pieces of the oviduct or intestines with the contents are crushed and ground in a mortar with sterile quartz glass or in a homogenizer. A 10% suspension in phosphate buffer solution is prepared from the crushed material and centrifuged at 1500-2000 rpm. within 30 minutes. The supernatant is aspirated with a pipette, transferred into sterile vials and 200 U of penicillin, 100 μg of streptomycin and 20 U of nystatin per ml are added to it. Exposure to antibiotics for 45-60 minutes at room temperature. In order to control the sterility of the material obtained, sowing is done on MPB, MPA, Kitt-Tarozzi medium and Sabouraud medium, followed by incubation of the crops for 10 days at a temperature of 37 ° C (and Sabouraud medium at a temperature of 20-22 ° C).

For serological research, blood serum is sent from birds aged 1-120, 160-180, 220-140, 300 days and from birds that are out of service by age, as well as from chickens with clinical signs of the disease (20-15 samples from each group). Blood samples in a volume of 3.0-4.0 ml are collected in separate tubes, pre-moistened with sterile saline solution, then placed in a thermostat with a temperature of 37 ° C for 20-30 minutes. The resulting clot is encircled with a metal knitting needle or a glass rod and kept in a refrigerator at 4-6 ° C for at least 3-4 hours. The settled whey is poured into clean numbered test tubes and sealed with rubber stoppers. Before use in work, the serum is heated in a water bath at a temperature of 56 ° C for 30 minutes. for inactivation of thermolabile inhibitors.

When sending eggs for examination from birds suspected of the disease, it is advisable to select substandard eggs (decalcified, depigmented). To prepare extracts, take 1.5 ml of yolk and suspend it in a test tube with 6.0 ml of physiological solution with a pH of 7.2-7.4. Then, 2.0 ml of dichlorethylene (chloroform) and 1.0 ml of ether are added to the test tubes, closed with rubber stoppers, the mixture is vigorously stirred by shaking, heated for 1 hour at a temperature of 37 ° C, periodically shaking and centrifuged for 15 minutes. at 2000 rpm. Obtained in test tubes is a transparent, slightly opalescent supernatant and is an extract of the yolk in the initial dilution of 1: 5, which is used as the test material.

To isolate the virus, duck embryos are used for 10-12 days of incubation, which do not contain antibodies to the EDS-76 virus. Before infection, embryos are ovoscoped and selected suitable for work, mobile, with a well-developed vascular system. For infection in the shell, after disinfection, two holes are punched: one in the center of the pug, the other on the lateral surface of the egg 2-3 mm below the border of the pug in the previously marked avascular space. The prepared suspension of the test material in a volume of 0.2 ml is introduced into each embryo through the lateral opening into the allantoic cavity. In this case, at least 4-5 embryos are infected with each sample of the material. After infection, the hole in the shell is filled with paraffin - initially the side, then the top. Infected and control embryos are incubated at 37 ° C for 96-120 hours. During incubation, embryos are ovoscoped once a day after 24 hours. Embryos that died in subsequent periods and remained alive on the sixth day after infection are cooled at a temperature of 4-6 ° C for 13-18 hours and opened. Extraembryonic fluid is collected from each of the opened embryos, antibiotics are added at the rate of 200 U of penicillin, 200 μg of streptomycin and 20 U of nystatin per 1 ml, and after contact, the second passage of the test material is carried out on developing embryos in the same sequence. Then the third passage is carried out. The extraembryonic fluid collected from the embryos of the third passage is examined in the RHA and RZGA for the indication and identification of the hemagglutinating EDS-76 virus. Intensive accumulation of viral hemagglutinin in organs and tissues of embryos begins 2-3 days after infection. By 5-6 days, the titer of the virus reaches its maximum values, in some cases 15-16 log HAU / 02 ml. At the same time, the death of embryos, as a result of the action of the virus, occurs quite rarely (1-2%). The virus can be cultivated in developing chicken embryos, but its accumulation is less intensive, regardless of the number of adaptive passages. Additionally, the reproduction of the virus in infected duck embryos during successive passages is controlled by the nature of the developed pathological changes in organs and tissues. Lagging of embryos in growth and development, hyperemia and edema of the skin in the head and neck region, punctate hemorrhages on the skin and in the subcutaneous tissue, clouding of the CAO, a slight increase in the liver and kidneys are noted.

The virus is also cultured in various cell cultures and suspensions of avian organ and tissue explants. The most commonly used cultures of fibroblasts of duck embryos and cultures of liver and kidney cells of chicken embryos. A 24-48-hour culture of primary trypsinized duck fibroblasts prepared by a conventional method and grown in glass vials (mattresses) or test tubes is used. The test material is additionally diluted in physiological saline to 10-1 and 10-3, and then each dilution of the material in a volume of 3 ml is contaminated with 3 vials with a monolayer. Infected and control vials are incubated at 37-38 ° C. To take into account the cytopathic effect, the vials are viewed under a low magnification microscope every 24 hours for 7 days.

The first cytopathic changes appear 36-48 hours after infection of cultures and are characterized by thickening of cell membranes, enlargement and rounding of the cells themselves. 96 hours after infection, the monolayer is destroyed, many dead cells float in the culture medium, while some of them are connected by long processes. When the cultures are stained with hematoxylin and eosin, large granular basophilic intranuclear inclusions are seen in them, merging into unformed accumulations of the basophilic mass. A large number of giant multinucleated cells are found, each containing 8-10 partially destroyed nuclei. The latter form vacuoles with remnants of nuclear matter. In the cytoplasm of individual cells, the formation of vacuoles and eosinophilic granularity is observed. The EDS-76 virus accumulates in the culture fluid, therefore, in order to obtain a higher concentration of viral particles in it, infected cell cultures at the final stages of virus accumulation are subjected to three successive freezing and thawing, using the resulting suspension in further studies when indicating the hemagglutinating EDS-76 virus.

For the indication and identification of the virus, RHA, RZGA, as well as MFA, ELISA, PCR are most often used.

The leading method for the indication of the virus in developing embryos or cell cultures is the detection of viral hemagglutinin in the RHA with a 1% suspension of chicken erythrocytes in the extraembryonic or culture fluid. Initially, put the approximate RHA on glass or in Petri dishes with a 1% suspension of erythrocytes in saline. A drop of erythrocyte suspension and a drop of vaccinated material are applied to a well-washed and degreased glass surface, mixed and observed for the appearance of flakes of agglutinated erythrocytes. A positive RHA appears within 3-5 minutes and is characterized by the formation of flocs of agglutinated erythrocytes. The results of a positive RHA in a preliminary experiment are confirmed by setting up a detailed (classical) reaction. In this case, 0.2 ml of sterile saline is added to each tube or well of the tablet, after which 0.2 ml of the test extraembryonic or culture liquid is added to the first tube or well, mixed with a pipette. Transfer 0.2 ml of liquid to the next tube or well. In this way, successive two-fold dilutions of the test material are prepared from 1: 2 to 1: 4096 or more. From the last test tube or well of the plate, 0.2 ml of material is removed into a disinfectant solution. Then, 0.2 ml of a 1% suspension of erythrocytes is added to each test tube or well with dilutions, the rack with test tubes or the plate is shaken for uniform mixing of the components and left at a temperature of 22-24 ° C. The reaction is accompanied by the control of erythrocytes for self-agglutination. To do this, add 0.2 ml of a 1% suspension of erythrocytes to 0.2 ml of saline (4 tubes or plate wells are more often used), mix and leave at the specified temperature. Agglutination of erythrocytes in this case should not be. Evaluate the results of the RHA in 30 minutes using the point system in crosses:

Four crosses (++++) - agglutinated erythrocytes settle to the bottom of the well in the form of an inverted umbrella with jagged jagged edges.

Three crosses (+++) - the umbrella of agglutinated erythrocytes is smaller and in its center there is a disc of non-agglutinated erythrocytes.

Two crosses (++) - the umbrella is well pronounced, but the central disc of non-agglutinated erythrocytes is enlarged and clearly distinguishable; when the tablet is tilted, it does not drain.

One cross (+) - slight agglutination of erythrocytes along the edges of the disc, which drains when the tablet is tilted.

Negative reaction (-) - there is no agglutination of erythrocytes.

For the hemagglutinating titer of the virus or one hemagglutinating unit (1 HAU), the greatest dilution of the virus is taken, in which there is an agglutination of erythrocytes by at least two crosses. For example: pronounced hemagglutination was obtained at a dilution of 1: 512, i.e. 0.2 ml of the isolated virus at a dilution of 1: 512 contains 1 HAU. It is permissible to set RGA (as well as RZGA) in plates for biochemical studies with the introduction of all components in a volume of 0.05 ml each.

The reaction of delay (inhibition) of hemagglutination (RHSA) is a serological method for identifying newly isolated strains of viruses with hemagglutinating activity and determining their antigenic relationship with reference strains. But more often it is used for retrospective diagnostics, for establishing the tension of post-infectious and post-vaccination immunity by quantitative determination of specific antibodies in the blood serum of chickens and adult birds. The methodology for stopping RZGA in order to identify the isolated EDS-76 virus and serological diagnosis of the disease differ insignificantly. To identify the pathogen, a known positive serum containing antihemagglutinins to the EDS-76 virus in a known titer is used. When carrying out diagnostic studies aimed at detecting specific antibodies, a standard inactivated antigen of the EDS-76 virus is used.

To identify the isolated virus, the titer of its hemagglutinating activity in the RHA is initially determined, a working dilution of the virus is selected, equal to 4 HAU (the method is given below), after which 0.2 ml of a positive EDS virus is added to 4 HAU of the virus in 0.2 ml of physiological solution. 76 sera in a dilution known to neutralize the amount of virus taken. After contact of the virus with serum for 30 minutes. at room temperature add 0.4 ml of 1% suspension of erythrocytes and after 30 minutes take into account the result. A delay in hemagglutination indicates the homology of the virus and serum species, i.e. will be a confirmation that the EDS-76 virus has been isolated. The absence of a delay in hemagglutination indicates that a hemagglutinating pathogen that is not the EDS-76 virus has been isolated.

The hemagglutination delay reaction for serological diagnosis of EDS-76 is performed in two stages.

At the first stage, the standard inactivated antigen of the EDS-76 virus is titrated for hemagglutinating activity in the RHA, and its working dilution is prepared and controlled. At the second stage, the RZGA itself is installed.

A working antigen dilution equal to 4 HAU is used in RZHA. To prepare a working dilution of the antigen, titration of the standard inactivated antigen of the EDS-76 virus is carried out in the RHA. As a result, the antigen activity is set equal to 1 HAU, after which a working dilution of 4 HAU is prepared. For this, an antigen with a known hemagglutinating activity is diluted with sterile saline as many times as is obtained from dividing by 4 the numbers corresponding to its hemagglutinating titer. So in our example, the hemagglutinating antigen titer (1 HAU), determined in the RHA, is 1: 512. To obtain a working dilution of the antigen, it must be diluted 128 times - (512: 4 = 128). Therefore, to prepare a working dilution of antigen with activity in RHA 1: 512, containing 4 HAU in 0.2 ml, you need to take 1 ml of the original antigen and add 127 ml of saline.

Before setting the main reaction, the correctness of the selected working dose of antigen is checked. To do this, 0.2 ml of sterile saline is added to five wells of a Plexiglass plate, starting from the second. Then, 0.2 ml of antigen in a working dilution is added to the first and second wells. 0.2 ml of liquid is taken from the second well with a pipette and transferred to the third, etc., thus preparing two-fold dilutions of the antigen. After that, 0.2 ml of 1% suspension of erythrocytes of chickens is added to each well, mixed, gently shaking the plate, and left at room temperature for 30 minutes. At the right choice the working dose of antigen (4 HAU) in 1, 2 and 3 wells containing 4, 2 and 1 HAU, respectively, intense agglutination of erythrocytes should be observed. In the fourth and fifth holes, agglutination should be no more than one cross. If the control results are different, it is necessary to re-titrate the standard antigen and re-prepare its working dilution.

The reaction of delayed hemagglutination is put in plexiglass plates or test tubes. In this case, 0.2 ml of saline is added to each well of the plate or test tube, then 0.2 ml of the test serum is added to the first well (test tube) of each row, and two-fold serial dilutions from 1: 2 to 1: 4096 are prepared using a pipette. ... After that, 0.2 ml of antigen in a working dilution is added to all wells (test tubes), the plates (stands) are shaken until the components are uniformly mixed and left at room temperature for 30 minutes to contact the antigen with serum antibodies. After the specified period, 0.4 ml of a 1% suspension of chicken erythrocytes is added to each well of the plate (test tube), the components are mixed and left at room temperature for 30 minutes. If the investigated blood sera contain specific antihemagglutinins to the EDS-76 virus, then the RSHA is considered positive and will be manifested by the absence of hemagglutination in certain wells, depending on the antibody titer. The titre of serum is considered to be its highest dilution, in which there is no agglutination of erythrocytes. The setting of the RZGA must be accompanied by controls:

0.2 ml of 1% suspension of erythrocytes of chickens + 0.2 ml of saline (there should be no agglutination of erythrocytes);

0.2 ml of serum specific positive to the EDS-76 virus + 0.2 ml of antigen in working dilution + 0.4 ml of 1% suspension of erythrocytes of chickens (there should be no hemagglutination);

0.2 ml of normal negative to the EDS-76 virus blood serum of chickens + 0.2 ml of antigen in working dilution + 0.4 ml of 1% suspension of erythrocytes of chickens (there should be a pronounced hemagglutination);

0.2 ml of the test blood serum (egg extract) + 0.2 ml of 10% suspension of chicken erythrocytes (there should be no hemagglutination).

Accounting for RZGA should begin with accounting for controls. Only with satisfactory results of the control reaction can the results of the reaction with the tested sera be taken into account. A diagnostic positive titer of antihemagglutinins to the EDS-76 virus is a titer of 1:16 and higher. Negative results of a study in RZGA of 15-10 blood serum samples or extracts of egg yolks, taken 2-3 weeks after the egg production decline, make it possible to exclude EDS-76 as one of the leading reasons for a decrease in egg production.

Diagnostic studies on EDS-76 are most reliable if one examines paired blood sera obtained from chickens before the onset of the disease (egg production decline), during and after recovery of egg production, roughly taken from laying hens at the age of 160-180, 200-140 days, after 300 days of age and at the end of the exploitation of layers due to age.

The immunofluorescence reaction (direct method of fluorescent antibodies, MFA) is used to identify the virus isolated on cell culture or avian embryos. Staining of preparations with FITC-labeled serum (conjugate of antibodies with fluorescein isocyanate) specific to the EDS-76 virus and their study in MFA is carried out according to the generally accepted method.

When isolating the virus in infected developing embryos of birds, preparations from the chorioallantoic membrane are used to identify the pathogen in the MFA. The detection of specific granular intranuclear inclusions of the EDS-76 virus antigen in infected cells indicates the identification of the isolated pathogen.

The method of enzyme-linked immunosorbent assay (ELISA) is based on the detection of an antigen-antibody complex as a result of the interaction of specific antibodies with an anti-species peroxidase conjugate, which can cause the decomposition of the substrate with the formation of a colored product of the enzyme reaction. To set up the reaction, use the "Kit for the diagnosis of EDS-76 by enzyme immunoassay" (VNIVIP), consisting of immunospecific and nonspecific components. The study of samples of the tested hen sera can be carried out in two ways: without titration of serum and with titration. If the study of samples of the tested blood sera is carried out without titration, then this makes it possible to conduct a qualitative assessment of the results in the ELISA reaction according to the principle of a positive reaction (specific antibodies to the EDS-76 virus were detected) or a negative reaction (no specific antibodies). If the study was carried out with titration, then the serum titer is taken as its maximum dilution, at which differences in the color of the contents of the wells with the samples of the tested sera are still observed in comparison with the wells of the negative control (negative serum). It is advisable to examine paired blood sera obtained from chickens before the onset of the disease (egg production decline) during the illness and after the recovery of egg production.

Electron microscopic diagnostics of EDS-76 is carried out by examining vaccinated material using the generally accepted method of negative contrasting, which, with a virus concentration in the material of 10 6 / ml, makes it possible to prepare preparations for viewing in an electron microscope within 30 minutes. With a lower content of the virus, it is concentrated by one of the generally accepted methods, or the method of immune electron microscopy is used using chicken serum homologous to the EDS-76 virus, which, with a slight increase in the processing time of the material, allows simultaneous serological identification of the virus.

The bioassay is carried out on 5 birds of 120-130 days of age. The test material is administered intranasally or intramuscularly in a volume of 0.3-0.5 ml for each of the five birds. The same number of chicks are kept in the uninfected control group. The observation period is 30 days. The presence of antihemagglutinins to the EDS-76 virus in a titer of 1:16 and higher in the blood serum of infected chickens is taken as a positive test, as well as pronounced deviations in egg productivity and the quality of the laid eggs. Autopsy reveals abnormalities in the development of the organs of the reproductive tract in an infected bird. If necessary, carry out histological and electron microscopic studies.

Treatment and prevention. Prevention of EDS-76 is based on strict observance of zoohygienic requirements, general veterinary and sanitary rules, conditions of keeping and feeding birds, in combination with specific prevention of the disease based on the use of a vaccine.

It is necessary to complete the parental herd at the expense of the offspring obtained from poultry farms that are free of EDS-76 or from those where specific prophylaxis of the disease is carried out. It is highly undesirable to keep mixed-age birds and chickens of various crosses together in the same room. Taking into account the possibility of infection of the course with the EDS-76 virus from ducks and geese, it is necessary to strictly territorially separate duck and goose farms from the premises inhabited by chickens, and to reduce to a minimum economic contacts between them.

If the complication of EDS-76 by opportunistic microflora is possible, it is advisable to give the bird antibiotics and nitrofuran preparations for 5-7 days. Sick and suspected birds are increased the amount of vitamins A, D3, E, B. The amount of calcium in the diet is increased by 2-3 times, up to 0.3% sodium bicarbonate (baking soda) is added to the compound feed.

For specific prophylaxis of EDS-76, an inactivated vaccine is used, which is administered to the bird intramuscularly or subcutaneously at the age of 90-120 days, preferably no later than 30 days before the start of oviposition. Immunity is formed after 14 days, reaching a maximum by 30 days. There are 1-, 2-, 3- and 4- and more valence vaccines, in various combinations, allowing to simultaneously vaccinate birds against EDS-76, Newcastle disease, infectious bronchitis, Gumboro disease, “big head” syndrome - pneumovirus infection, reovirus infection, respiratory mycoplasmosis, used depending on the epizootic situation in the poultry farm. After 21-28 days, it is necessary to determine post-vaccination immunity and, if necessary, urgently revaccinate the bird.

Egg drop syndrome-76 (EDS-76) - Egg drop Syndrome-76 (EDS-76) is a viral disease of chickens, characterized by a decrease in egg production, a change in the shape of eggs, the quality and pigmentation of the shell, and a violation of the protein structure.
Historical background, distribution, economic damage. In 1975, in a number of Western European countries (Holland, England, Northern Ireland, and somewhat later in Italy, France, Sweden, Denmark, Hungary and other countries), a new chicken disease appeared, characterized by a decrease in egg production, the laying of shellless eggs or eggs from thinned depigmented shell. The disease spread especially rapidly in areas with a high concentration of poultry farming.

Due to the characteristic features of this disease, in the literature it is called "egg drop syndrome-76" - Egg Drop Syndrome-76 (EDS-76). It was first described by J. Van Ecke et al., 1976.
Having quickly spread, it was registered in Japan, India, Australia, Nigeria, Brazil, Mexico, USSR, Taiwan.
The hypothesis of the occurrence of EDS-76 was proposed by a number of scientists who believe that the causative agent of the disease is the duck virus, which does not cause pathology in natural "hosts". Chicken flocks were infected with the virus as a result of the use of the Rispen strain vaccine against Marek's disease, prepared using a culture of duck fibroblast cells contaminated with adenovirus. The virus quickly adapted to a new "host" for it and showed its pathogenic properties. The authors explain the origin of the EDS-76 causative agent from ducks by the fact that the disease first appeared in Holland, a country of intensive duck breeding.
According to statistical data, in 1993 in Russia, EDS-76 was first diagnosed in chickens and treatment and prophylactic measures were taken in the following regions: Leningrad, Moscow, Sverdlovsk, Chelyabinsk, Omsk - for the number of chickens 2 140 774. Of these, the largest percentage of patients chickens accounted for the Leningrad region (67.1%), the Chelyabinsk region (15.9%), the Omsk region (12.6%).
In 1994, there was a further spread of STYA-76 - in the Moscow, Leningrad, Kalinin, Vladimir, Vologda, Tula, Yaroslavl, Sverdlovsk, Chelyabinsk, Nizhny Novgorod, Perm, Omsk, Ulyanovsk, Orenburg, Smolensk, Oryol, Murmansk regions, including in a number of autonomous republics, only 18,452,923 chickens have been vaccinated. The largest percentage of patients and virus carriers fell on the Moscow (21.1%), Leningrad (17.1%), Omsk (15.8%), Ulyanovsk (10%), Nizhny Novgorod (8.75%) regions.
In 1995, the disease was reported in the above regions, as well as in Bryansk, Pskov, Arkhangelsk, Ryazan, Kaluga, Volgograd, Kursk, Belgorod, Novosibirsk regions, Krasnoyarsk Territory, etc. in a number of autonomous republics, 52 270 669 chickens were vaccinated. Of these, the largest percentage was in the Krasnoyarsk Territory (15.5%), Moscow (10.9%), Perm (6.2%), Ulyanovsk (4.2%), Nizhny Novgorod (3.6%), Novosibirsk (3 %) area.
Egg Production-76 Syndrome causes significant economic damage. According to foreign researchers, the damage consists of an average loss of 15 eggs per laying hen (on average, up to 50 eggs are discarded from breeding hens), the laying of up to 15% of shellless eggs, up to 12% of eggs with a blood ring, a 7% decrease in hatchability, and their low viability, which leads to an increased up to 10% chick mortality in the period up to two weeks of age. The damage from STYA-76 is compounded by the cost of restrictive measures, especially those related to breeding farms.
Causative agent. The disease is caused by a DNA virus from the Adenoviridae family.
The EDS-76 virus was first isolated in 1976 by J. Me. Ferran in Northern Ireland. Currently, this strain of the pathogen is known under the number "127". Almost simultaneously in England, Bexandale isolated a similar virus called "BC-14" from the leukocytes of sick chickens. Later, the EDS-76 virus was isolated in Hungary, called "BB / 78".
The causative agent of the infection is duck adenovirus, which, in contrast to the known serotypes of avian adenoviruses, has the ability to agglutinate erythrocytes of chickens, ducks, geese, turkeys, and the Mexican virus EDS-76 (strain HO-1) - erythrocytes of humans, peacocks and pigeons.
Morphologically, the virion is a particle about 80 nm in diameter, with filamentous processes 25 nm long and 2 nm in diameter, ending in clavate thickenings.
The virus reproduces well in tissue cultures of the liver and kidneys of chicken and duck embryos, in a culture of fibroblasts and in the allantoic cavity of developing duck embryos. During reproduction in cell culture, the virus causes a cytopathic effect (CPE) and forms intranuclear inclusions characteristic of avian viruses. It was found that duck embryos and cell cultures prepared from them are a more adequate model for the virus than chicken embryo cell cultures. This property is successfully used for virus isolation, obtaining vaccinated material in high titers in the production of diagnostics and vaccines.
The causative agent of EDS-76 is relatively resistant to ether, chloroform, temperature factors. When the virus is heated to 56 ° C for 30 minutes, infectious activity
decreases by no more than 50%. Heating up to 70% causes a loss of infectious and hemagglutinating activity after 10 minutes. In a frozen state at -25 ° C, the virus remains viable for more than 3 years. The virus is relatively stable at a pH of 6.0-8.0.
Epizootology. Laying hens of all breeds are susceptible to the disease with the maximum manifestation of the disease during the period of the highest egg production (200-240 days), but it is possible to damage the bird at any period of the productive cycle. The disease spreads quickly when poultry is kept on the floor. Laying hens are more susceptible to the disease of high-yielding crosses, including Hyssex Brown, Loman Brown, Isa Brown. It is believed that meat poultry is more susceptible to disease than egg poultry. Under natural conditions, the EDS-76 virus is widespread among domestic and wild ducks, at the same time it is apathogenic for them, without causing disease; however, they can also be a source of infection for chickens. Despite the low contagiousness of the disease, there is a danger of introduction of the pathogen into the territory of the economy by wild birds: pigeons, sparrows.
Broilers can be a potential source of infection, according to some authors. The main route of spread of the pathogen is transovarian vertical transmission. When the first clinical signs of the disease appear, horizontal spread of the pathogen is noted.
Eggs are especially intensively infected during the period of viremia, which coincides in time with a decrease in oviposition. During the same period, the virus is excreted in feces, pharyngeal and tracheal mucus. It is possible that it is isolated with the sperm of cocks. It is also possible for the virus to spread when vaccinated against other infections.
For experimental reproduction of the infection, oral intraconjunctival and intracloacal routes of administration are used, as well as the joint keeping of sick and healthy birds.
Specific predisposing factors for the onset of infection, other than age-related, have not been established. An epizootological feature of syndrome-76 is the ability of the virus not to manifest itself in the body until the bird reaches puberty. The virus is activated by stress caused by the onset of lay. After 40 weeks of age, the bird does not release the virus, but the blood contains specific antibodies.
Chickens raised from chicks hatched from infected eggs and infected in the first days of life do not drop egg production, although they may not reach the predicted level. Such birds remain virus carriers throughout the entire growing period. The virus is reactivated and released only with the onset of oviposition at the age of 22-26 weeks. A decrease in egg production is noted only in chickens that are seronegative during the entire rearing period, that is, the more negatively serologically reacting chickens in an infected flock, the more sharply the syndrome of decreased egg production manifests itself.
Pathogenesis. During the period of latent infection, the virus persists in the intestine. Viremia is one of the stages of adenovirus infection. It is believed that the reactivation of the virus occurs due to a change in the hormonal profile at the beginning of oviposition, which is considered a stress factor. The duration of the period of persistence and isolation of the virus is inversely related to the age of infection in chickens. The earlier they become infected, the longer these periods are.
During the period of viremia, viral particles are found in the epithelial cells of the mucous membrane of the oviducts and in other organs. Apparently, the virus has a direct effect on the glandular epithelium of the uterus, which determines the clutch of shellless eggs or eggs with a thin and fragile shell.
There is evidence that the virus disrupts the "sodium-potassium pump" of the glandular cells of the uterine mucosa. So, in chickens laying eggs with a broken shell, the concentration of sodium in the contents of the uterus is significantly increased, and calcium, potassium and magnesium is reduced compared to intact or infected, but laying eggs with normal shell chickens. An increase in acidity can lead to calcium dissolution and impairment of shell formation.
Clinical signs. The clinical picture of the disease is not very pronounced. There are no characteristic symptoms. In some cases, sick chickens have diarrhea, some depression, ruffled feathers, anemia, and a decrease in feed intake.
At the peak of the disease, weakened breathing, liquid greenish droppings are observed for 1-2 weeks. In the later stages of the disease, cyanosis of the earrings and ridge is noted. The most characteristic typical symptom of the disease is a decrease in egg production and obtaining a defective egg. Egg productivity decreases on average by 15-30%, and in some disadvantaged herds - up to 50%. At the same time, the decrease in egg production proceeds in a certain pattern - the entire period of decline is 6-7 weeks, of which 4-5 weeks fall directly on the decline, and 2- 3 subsequent weeks - during the recovery period. With cage keeping, the productivity of chickens is restored almost completely or remains 1-3% lower than planned, and with floor keeping, as a rule, it does not reach the initial level by 7-10%.
A change in the quality of eggs obtained during the period of illness is manifested in the fact that a sick bird lays an egg without a shell for 6-8 weeks or with striped rough formations on the surface of the shell. The number of "marble" eggs increases significantly, the percentage of eggs broken and notched increases. The incubation qualities of the eggs deteriorate, while the fertility of the eggs, the hatchability and the viability of the chickens decrease.
Changes in shell quality, the so-called "fatty egg", are most often observed in poultry and brown layers. In chickens of the White Leghorn breed, "Hisex White", the protein part of the egg is more susceptible to change, and not the shell. In these breeds of chickens, the protein becomes watery, cloudy. The EDS-76 virus causes edema of the glandular tissue of the uterine villi, followed by degeneration of the mucous epithelium of the uterus, which leads to insufficient resorption of calcium and leads to acidosis as a result of a decrease in the pH of the secretions of the uterine mucosa and oviduct. This, in turn, causes the neutralization of calcium carbonate formed by the shell gland, which leads to the formation of shellless eggs, eggs with soft, thinned, depigmented shells.
The mortality of poultry with the syndrome of declining egg production-76, even at the peak of the disease, is insignificant. Mortality among adult layers can be 3-5%, mainly due to yolk peritonitis and an increased number of pecking.
Pathological changes. The main pathomorphological changes in EDS-76 are localized in the organs of the reproductive tract - the ovary, oviduct, uterus.
When opening a dead and forcedly killed adult bird infected with the EDS-76 virus, in all cases, a small number of maturing and mature follicles in the ovary are noted. Ovarian atrophy is often observed, the presence of lumpy, deformed and atrophied follicles in them, filled with a mass of curdled consistency of gray-yellow or greenish color. There are follicles with hyperemia or hemorrhages in the connective tissue capsule. The oviduct of the affected layers, as a rule, is shortened, its wall is thinned, in some cases with foci of hyperemia. Taking into account the localization of the process and the etiology of the disease, some authors propose to call it "adenoviral salpingitis".
In many cases, at autopsy, a change in the liver is noted, which increases in size, is edematous, has a flabby consistency and a yellowish-clay color. There is a change in the gallbladder, which is enlarged, filled with bile of a watery consistency, light green in color. A hypertrophied liver and a violation of the normal function of the gallbladder lead to general digestive upset, which is expressed in the laxity and immobility of the intestine, filled with a frothy greenish and watery consistency of undigested food.
Histological changes. Histological examination of the organs and tissues of the affected bird reveals the main changes, mainly in the organs of the reproductive tract, as well as in the liver.
So, in the ovaries, lymphoid-histiocytic and mononuclear proliferates, hyperemia, dystrophic, and at later stages of the disease and necrotic changes in the epithelial layer of individual follicles are noted. In the protein part of the oviduct, foci of mononuclear lymphoid infiltration are also found, which forms perivascular in the connective tissue septum of the folds of the mucous membrane and extends to its glandular tissue. In the uterus, there are edemas of the mucous membrane and focal lymphoid-histiocytic proliferates. In the liver, hyperemia, the presence of perivascular proliferates, dystrophic changes in hepatocytes, more often of a fatty nature, are found.
Immunity. EDS-76 virus strains cause the formation of specific antibodies in infected poultry - antihemag-glutinating, precipitating and neutralizing antibodies - on the 7-14th day after infection.
Diagnostics. The diagnosis of EDS-76 is established on the basis of epizootological, clinical, pathological data and laboratory results.
Evaluation of poultry egg production graphs is important for making a preliminary diagnosis. Since the EDS-76 virus provokes a decline in egg production by 15-30% in poultry at the age of 200-240 days, the decrease in productivity in laying hens at other times, especially after 300 days of age, is the cause of the action of other factors. Of no small importance in making a diagnosis is an assessment of the quality of eggs - their shape, color and quality of the shell, the quality of the protein.
Laboratory methods are decisive in making a diagnosis for EDS-76.
1. Identification of specific antibodies in the blood serum of sick and suspicious laying hens in the reaction of hemagglutination delay (HAG) and using enzyme-linked immunosorbent assay (ELISA).
For the study, paired blood sera are taken, starting from 160-180 days of age, in any case, the beginning of the decline in egg production. In the case of detection of antihemagglutinating antibodies in titers of 1: 4 and higher, it is concluded that the causative agent of EDS-76 is persistent.
2. Isolation of the virus from the pathological material with its subsequent identification in the RZHA.
Isolation of the virus from pathological material is most expedient to carry out in the developing 10-12 day old duck embryos or in the culture of cells of fibroblasts, liver, kidney of duck embryos.
3. Differential diagnosis. In the differential diagnosis of EDS-76, a decrease in egg production caused by the CELO viruses, infectious bronchitis, Newcastle disease and violations of the conditions of keeping and feeding is excluded.
Specific prophylaxis. For the prevention of EDS-76, monovalent and associated forms of vaccines based on mineral and oil adjuvants have been developed and introduced into the practice of poultry farming. The bird is vaccinated once intramuscularly at the age of 100-110 days.
Associated inactivated vaccines against infectious bronchitis, IBD, Newcastle disease and EDS-76 are now widely used.

A person who breeds chickens for eggs and meat on his site should not only study the rules for breeding and keeping them, but also have an idea of ​​the diseases that can affect his feathered pets. And not only to know about them, but also to be able to react in a timely manner and correctly, so as not to miss the conditions that are dangerous for the life of birds, as well as for human health. This article discusses a common disease called egg drop syndrome-76.

There are diseases of poultry that are transmitted from one species to another without severe symptoms until a victim is found that has a sensitivity to the causative agent of the disease.

Did you know? Chickens were first domesticated about three thousand years ago in the territory where modern Ethiopia is located.

Egg Drop Syndrome-76 (EDS-76) was first discovered and described in the Netherlands in 1976. It is believed that the virus is carried by ducks: domestic and wild, they themselves, however, are not susceptible to disease.

The fact that no antibodies to the pathogen were found in serum samples obtained from chicken blood before the specified year is considered evidence that this disease arose during this period.

Subsequently, virus strains identical to the original, strain-127, were isolated in various progressive countries: England, France, Italy, Japan, Hungary. This means that the detected disease began to spread throughout the world.

EDS-76, or adenovirus disease (Egg drop Syndrome-76), is characterized by the fact that laying hens due to damage to the reproductive system decreases egg productivity, the eggs change their shape, their quality deteriorates, the shell is fragmentarily depigmented and softens or is completely absent, protein structure is disrupted.

The causative agent of this pathology is a DNA-containing adenovirus (Adenoviridae), hence the other name of the disease. This microorganism does not belong to the known types of avian adenoviruses and is capable, in contrast to the mentioned ones, of gluing (agglutination) of erythrocytes of many, including domestic, birds.

Did you know? The chicken will not lay in the dark, even if the time is right. She will wait until the day comes or the lights are on.

After the chicken has suffered this disease, it acquires antibodies that it can transmit to offspring through the eggs.

The microorganism is sensitive to formaldehyde, but it cannot be destroyed:

• ether;
• chloroform;
• trypsin;
• phenol solution 2%;
• alcohol solution 50%.

At 50 degrees, it is active for 3 hours, at 56 degrees - one hour, at 80 degrees - half an hour. It is known that the pathogen multiplies in the cells of the epithelium of the oviduct and, at the same time, the formation of eggshells of normal quality is disturbed.

Did you know?The one-day-old chick has a set of reflexes and skills that match that of a three-year-old human child.

A bird that has undergone a disease after recovery may experience:

• swelling of the oviducts and atrophic processes in them - shortening and thinning;
• in some cases - cysts;
• changes in the liver: increase in size, yellowing, flabby structure;
• enlargement and fluid filling of the gallbladder.

Causes of the onset of the disease

A chicken of any breed and any age, starting from a productive one, can get sick, however, the “favorite” age for the manifestation of the virus is the peak of chicken productivity: 25-35 weeks. Chickens of pedigree breeds, as well as laying hens belonging to the meat type, are more susceptible to it.

The manifestations of the disease are the brighter, the higher productivity is expected from an individual in accordance with its breed characteristics.
Adenovirus transmitted transovarially (through an egg laid by an infected laying hen) can remain asymptomatic in the body of a young bird until the time when its body experiences stress, for example, the start of laying. At the right moment for him, it is activated, reducing the egg production of the chicken. This transmission method is called vertical.

It is noteworthy that a chicken hatched from an infected egg or infected with the EDS-76 pathogen in the first days of life will not show vivid manifestations of the syndrome at the peak of productivity, however, one should not expect high egg production from it.

The possibility of horizontal infection also remains:

• contact - by means of clothing and footwear of people, transport, household items and care;
• sexual - through the sperm of a cock;
• fecal-oral - through droppings and discharge from the nasal and oral cavities of infected individuals;
• by vaccinating poultry against other diseases.

The carriers of the EDS-76 causative agent are infected and recovered chickens, ducks and geese, both domestic and wild, as well as other waterfowl. Wild birds can carry disease over great distances through contaminated feces.

Important! In the case when the bird is kept crowded, in close contact, the spread of the virus is significantly accelerated and infection of the entire flock can occur in 1-14 days. On the other hand, layers isolated from each other by partitions are able to remain healthy for a long time, even when they are close to an infected individual.

Economic damage

STYA-76 brings significant economic damage to both private farms and large industrial enterprises. During the illness, culling from one laying hen is 10-30 eggs, and in breeding birds it reaches 50. This means 17-25% damage.
It takes from 4 to 6 weeks to restore the productivity of one individual, if it is contained in the cage. In chickens kept on the floor and in contact with other individuals and their biological material, egg production may never be restored to its original level by 6-12%.

As for the hatching eggs laid by infected individuals, many of them are simply unsuitable for hatching young animals due to their too fragile shell. In addition to the fact that a large percentage is rejected already at the initial stage, hatchability of chicks decreases. The level of their survival in the first days after hatching is also reduced.

Although in our time there is much more information about this disease, and enough experience has been accumulated in the fight in comparison with 1976, some questions are still controversial and do not have an unambiguous answer.

Important! The syndrome is widespread in those countries where highly developed industrial technologies of poultry farming are used, and the greatest damage is caused to breeding farms.

Symptoms

Until the beginning of the productive age, in an infected individual, the pathogen resides in the intestine and does not manifest itself in any way. When the time comes and the hormonal background of the chicken changes to ensure egg production, the virus is activated and the stage of viremia begins, that is, the circulation of the virus in the body through the bloodstream.

Reaching the epithelium of the mucous membrane of the oviduct, the virus contributes to the imbalance of minerals: sodium, potassium, magnesium, calcium and others, as a result of which the chicken lays eggs with a shell that is too thin, deformed, or even completely absent.

Did you know? In addition to its reproductive role, a rooster in a chicken herd performs a number of important social and administrative functions: control over the daily routine, prevention of conflicts, protection from danger, even if the enemy is obviously superior in strength and size.

For all the severity of the infection, chickens rarely show any signs of disease.

Occasionally, more often in an insignificant form, the following can be observed:

• signs of general intoxication - weakness, fatigue and others;
• decreased appetite;
• diarrhea and the presence of a green tint in the droppings;
• anemia;
• weak breathing at the peak of an acute condition;
• bluish shade of scallop and earrings.

The main sign and symptom is a sharp decrease in productivity, the laying of thin, deformed eggs of very poor quality. The protein in such a product is watery and cloudy. Chickens hatched from these eggs have low viability and die in large numbers in the first days of their life.
Symptoms can vary depending on the breed of chicken:

• "Fatty egg" and reduced shell quality are more common in brown crosses and broilers;
• protein change. Its thinning and haze is more typical for white crosses.

Important! Death is not a common symptom of this disease, and its rate is rarely higher than 5%. The cause is mainly yolk peritonitis.

Diagnostics

In order to make a preliminary diagnosis and keep a subsequent record, it is necessary to develop graphs demonstrating the development of egg production, taking into account the fact that, due to adenovirus, a decrease in egg production occurs in layers of 200-240 days of age.

In the event of a drop in productivity in an individual over 300 days of age, the cause is most likely some other factor.
In any case, before diagnosing "egg production syndrome-76", you should exclude:

• bronchitis of infectious etiology;
• poisoning with various substances;
• inadequacy of the diet;
• other factors that can provoke a decrease in egg production.

How and where to go

If a virus is detected at an industrial enterprise, the economy is transferred to the category of dysfunctional and appropriate restrictions are imposed: measures for mechanical cleaning and disinfection, vaccination, culling, and the like.

Finding a chicken with suspected EDS-76 in a private chicken coop is a reason to invite a veterinarian who will examine and vaccinate, and will give recommendations.

What surveys will be carried out

The diagnosis of "adenovirus infection" is made on the basis of research:

• epizootological;
• clinical;
• pathological;
• laboratory.

For analysis, the laboratory examines:

• oviduct;
• ovaries with follicles;
• the rectum and its contents;
• blood;
• washings from the nasopharynx and cloaca.

It is preferable to conduct research in the first days of the disease (3-5 days), and use material from a bird that died or was slaughtered no more than 2 hours ago.

It is advisable to take blood for the isolation and study of its serum from individuals of the following groups (15-20 samples from each):

• 1-200-day-old individuals;
• 160-180-day-old individuals;
• 220-day-old individuals;
• 300-day-old specimens;
• retired elderly individuals;
• specimens with signs of the disease.

Did you know? Chickens have their own "language", capable of transmitting about 30 different signals to other individuals with the help of sound. There is even a "mother" language with which the hen communicates with the offspring. Moreover, a chick that has not yet hatched, a few days before this event, communicates with a hen through the shell, using up to ten different signals for this.

As for eggs, it is desirable to investigate substandard samples with a violation of the structure of the shell and / or contents.

How to treat

As with many other viral diseases, there is no specific treatment. It is recommended to focus on the completeness of the diet, its saturation with essential amino acids, vitamins and minerals. The production of antibodies begins on the 5-7th day of the disease and lasts for 2-3 weeks, after which the individual receives lifelong immunity.

The necessary measures include the mandatory isolation of the first sick layers from the rest of the flock, especially if floor keeping is practiced. In this case, it is necessary to observe the rest of the bird for signs of symptoms.

If the nature of the disease is not isolated, quarantine measures are necessary. An unhappy bird is slaughtered, the biological material taken from it is sent for analysis for laboratory confirmation of the diagnosis.

The chicken coop is treated and disinfected with a 2% formaldehyde solution. Eggs for incubation are used after a 2-month break. At the very beginning of the disease, it is advisable to introduce a vaccine: liquid sorbed or emulsified inactivated.

Important! It is very important to track the onset of the disease and not trigger the situation: this can help avoid many problems associated with the spread of the virus in the chicken herd.

This measure can be effective in skipping the phase of viremia - the spread of the virus through the bloodstream throughout the body. Consequently, the pathogen will cause less harm to the bird, will not be present in the body's secretions, in addition, this measure allows you to improve the quality of eggs and the productivity of the bird.

Prevention and vaccine against the virus

To prevent such an unpleasant disease as egg production syndrome-76, vaccination is used, which prevents the viremia phase, which improves the productivity and quality of the eggshell.

Individuals of 16-20 weeks are vaccinated by injecting the drug subcutaneously or intramuscularly, and after 2 weeks the bird develops immunity lasting one year.

The following vaccines are used for immunization:

• liquid inactivated;
• emulsified inactivated;
• associative inactivated.

Preventive measures are based on the implementation of veterinary and sanitary rules in order to prevent the introduction of the pathogen from the external environment. To hatch chickens, eggs taken from layers over 40 weeks of age are used, and you should first make sure that their analyzes are normal.

The bird, in whose blood the pathogen is found, is slaughtered. The fact that a virus has been detected indicates its presence on the farm. In this case, you need to monitor your chicken coop and take the necessary measures in time.

To reduce the risk of an outbreak in your chicken coop, you need to:

• comply with sanitary standards;
• keep birds in isolation by age groups;
• keep the chicken herd separately from the goose and duck herd;
• from time to time, clean and disinfect the premises, as well as equipment.

Video: what to do when a chicken is sick

Did you know? Chickens are capable of emotions: sympathy, sadness. In addition, they have a sufficient level of intelligence to remember the appearance of about a hundred other creatures, and also use their experience and information about the environment to make decisions. 5 once already
helped

Converter