Chronic illness birds, caused by intracellular infection, is respiratory mycoplasmosis. It primarily affects the respiratory organs and air sacs of birds. The pathogen can cause an entire epidemic in the poultry house and harm chickens and their egg production. There is a high mortality rate among broilers and young animals.

Every chicken can become infected with mycoplasmosis.

The source of the pathogen is in the soil, on plants and in manure. Mycoplasmosis is neither a bacteria nor a virus, but occupies an intermediate position, so treatment of the disease is quite complex.

There is a pathology similar to mycoplasmosis that occurs in recently hatched chickens. This is an infectious bursal disease. Otherwise known as Gumboro disease, it is highly contagious. viral disease, which affects the kidneys and bursa of Fabricius in birds. Hemorrhages also occur in muscle tissue. The bursal disease virus is capable of suppressing the immunity of chickens, destroying B-lymphocytes, thereby sharply reducing the protective functions of the body.

Gumboro disease poses a serious threat to the agricultural economy. It always flows into acute form, is characterized by high mortality of chickens, and treatment does not give the desired result.

Pathogenesis of respiratory mycoplasmosis

Mycoplasmosis in chickens is a common disease. Adults often carry this pathogen while remaining healthy. If the infection causes inflammation of the joints, compaction and swelling will form there. Multiple fibrous formations form in the tissues of the bird. Characteristic degenerative changes also occur in the liver parenchyma.

Conjunctivitis is common with mycoplasmosis

Very often, respiratory mycoplasmosis develops along with echinococcosis. If two of these infections are found in the body of birds, treatment of the disease becomes significantly more complicated.

Initially, the infectious agent enters the lungs of chickens, no manifestations are visible. Typically, the process of mycoplasma reproduction begins under the influence of stress, hypothermia, or as a result of improper care of the bird. Also, a provoking factor can be a decrease in immunity and eating disorders.

A greater predisposition to the development of infectious mycoplasma is observed in broilers. These chickens are raised indoors, stuffy rooms, where litter quickly becomes wet. From lack fresh air, outbreaks of the disease in broilers occur frequently and are severe. Arises large number foci of infection in the poultry house, which is why the epidemic is developing rapidly.

General signs of mycoplasmosis

The course of this disease in poultry is quite complex. The chronic nature of the disease greatly weakens the chickens’ body and the longer the disease continues, the less chance there is of a favorable outcome. Symptoms, treatment and course of the disease largely depend on the age of the bird, the body’s resistance and immunity. The incidence rate in young chickens is much higher than in adult chickens.

This is how chicken mycoplasmosis manifests itself

Reproducing in epithelial cells upper respiratory tract, the virus begins to spread throughout the body through the bloodstream. Respiratory mycoplasmosis causes the following symptoms in birds:

• from the outside respiratory system: difficulty breathing, wheezing, cough;
• from the digestive system: lack of appetite, weight loss;
• there is discharge of serous fluid from the nose;
• state of lethargy and lethargy;
• temperature is normal or low-grade;
• reduction in the growth rate of chickens.

Weakened by illness, chickens look for a secluded place where no one will disturb them. Intoxication is especially bad in broilers. At the same time, there is general inhibition; when startled, no reaction is observed. At severe course complications such as infectious sinusitis and joint inflammation may occur. In this case, the chickens begin to limp and try to move less.

Inspection reveals inflammatory process and hardening of joints. The disease often affects the eyes of birds, causing symptoms such as increased tearing, inflammation and suppuration. The chickens have practically no visible symptoms, but they die quite quickly.

Vaccination of poultry against bursal disease

Only vaccination of all individuals in the poultry house makes it possible to prevent further development of the disease. To ensure that the bird's body has lasting protection against infection, live and inactivated vaccines are used. It is also carried out in order to prevent mass epidemics of respiratory and infectious mycoplasma.

This is how chickens are vaccinated

Chicken vaccine against mycoplasmosis is immunotropic pharmacological agents and made from the culture of Mycoplasmagal lisepticum (strain “S6”). It promotes the emergence of immunity to this pathogen. Broilers are vaccinated when 10 days have passed since birth. Immunity is formed within 28 days and works for 8-9 months.

All chickens in the coop are vaccinated against such a serious virus as bursal disease. For this purpose, live and inactivated vaccines are used. The vaccine is administered subcutaneously, in an amount of 0.7 cm3, into the neck, tailbone, or chest muscle of chickens. Immediately before use, the drug is kept for 6-9 hours at temperature conditions 20-28 degrees. Then shake the bottle well so that there is no sediment in the solution. Before vaccination is carried out, the injection site is treated with 70% alcohol or another antiseptic. After 28 days, it is necessary to monitor the intensity of immunity to the virus. To do this, you need to examine about 28-30 blood serum samples.

Treatment of chickens for mycoplasmosis

If birds have not been vaccinated against mycoplasmosis, the disease can affect the entire poultry house. Then the treatment will be very expensive. It is much easier to prevent an epidemic than to deal with the consequences. Carrying out the necessary preventive measures, the risk of the source of the disease is significantly reduced.

Mycoplasmosis is treated with antibiotics. Drugs used include streptomycin, oxytetracycline, and aureomycin. For convenience, the antibiotic is added to a ton of feed in an amount of 200 grams. This should be enough for several days. Tylosin is injected subcutaneously into each bird at 3-5 mg per pound of body weight.

Antibiotics are sometimes added to drinking water

Alternatively, you can add it to water. Calculation: 2-3 grams per gallon of water. The treatment is quite painstaking and difficult to carry out from the point of view of keeping poultry. During the quarantine, everything is carried out in the poultry house necessary methods disinfection, and sick birds are transferred to an isolated place. It is noted that antibiotic treatment does not always give the desired effect. The use of antibiotics and nitrofuran drugs does not provide full recovery birds. However, no other known treatments have yet been invented.

Such difficulties in selecting drugs are due to the fact that the causative agent of the disease is capable of long time be inside the cell. Moreover, this virus is absolutely not susceptible to the action of cells immune system(phagocytes). Antibiotic therapy can only reduce the number of sick individuals and stop the symptoms of the disease.

Tetracycline drugs are analogues of streptomycin and are more effective antibiotics in the fight against infection. Immunomodulators are also used to help adjust the bird’s immune system to direct it to fight the disease.

Treatment with Furacycline-M showed good results in the fight against mycoplasmosis. This etiotropic drug contains a set antibacterial agents, vitamin B, macroelements and amino acids. In total, these substances strengthen the body and immunity of birds.

Regarding the prevention of infectious bursal disease, strict sanitary measures and disinfection of premises are carried out for three months. Great value for prevention, it has proper herd recruitment, plus proper, balanced nutrition.

Gumboro disease poses a serious threat to industrial poultry farming, causing high mortality and loss of productivity in both meat and egg chickens. The use of intermediate plus vaccines protects chickens from acute and subclinical forms of this disease. To study chicken blood sera for the presence of antibodies to the Gumboro disease virus, the ELISA method has been used for more than 15 years, which has a number of advantages, for example, it is fast and cheap, but its main advantage is that the method is reliable and standardized. This article presents the results of a study of broiler blood serum by ELISA during the growing period (from the 1st to the 45th day).

Protection throughout the growing period

One of the main objectives of vaccination against Gumboro disease is to protect chicks throughout the rearing period. Day-old chicks are protected from MA disease, which they received from chickens of the parent flock. Broiler chickens become sensitive to the Gumboro disease virus by 20 days of age, and egg-laying chickens by 30 days of age. The presence of MA in chickens early age prevents their vaccination, since MAs neutralize the vaccine virus (Fig. 1).

It has been proven that when immunizing chickens with a high level of MA, the vaccine virus does not cause seroconversion. When vaccinating chickens with a critical level of MA (the level of MA that can overcome the vaccine strain), a good immune response is formed that prevents clinical and sub clinical signs Gumboro disease - mortality, hemorrhagic inflammation of the bursa, decreased productivity.
The chickens in early period(Fig. 2) the average antibody titer decreases, which reaches its critical value in chickens at 12 days of age (559). The chickens were vaccinated the next day. During a serological study, the first antibodies were detected on the 4th day after vaccination. The average antibody titer has reached its maximum value at 26 days of age (3338) and remained at a high level until the slaughter of the bird (3398). The field virus can also cause seroconversion, but in this case, along with the latter, clinical signs appear and the productivity of chickens decreases. When assessing antibody titers (Fig. 3), it is also very important to take into account their homogeneity. High homogeneity indicates good quality vaccination of chickens.

Determining the date of vaccination

No less important task vaccination of chickens - to create a smooth transition from passive immunity (PA) to active. However, in real conditions, calculate exact date Vaccination is only possible if the chicks come from the same supplier and from a homogeneous parent flock. Blood serum for serological study, as a rule, taken from chicks during the first three days of life.
Vaccination time is calculated using the Kohavena formula (for broiler chickens) or Deventor (calculation based on the decay period of antibodies).
These methods are often used in laboratories because they come with software equipment. The date of vaccination determined in this way must be confirmed veterinary specialist or manager, in accordance with real situation at the factory.
In this experiment, chickens were immunized with the Cevac® IBD L vaccine by feeding at 13 days of age (Ceva Sante Animal, Libourne, France). The average antibody titer in chickens before vaccination at 12 days of age was 559, with more samples (8) were in the first group with antibody titers from 0 to 396 (Fig. 4). Coefficient of variation 97%. Chickens were immunized once with the intermediate plus vaccine Cevac® IBD L, since it overcomes the MA level at a dilution of 1:500.

Seroconversion and duration of antibody circulation

When studying blood serum samples from chickens at 26 days of age (2 weeks after vaccination), a high and uniform seroconversion was noted (Fig. 5), with a coefficient of variation of 32%. A positive titer of antibodies against Gumboro disease is considered to be from 1000 to 2000. In this study the average antibody titer was 3338 and all samples were positive. The results of an ELISA study depend on many conditions - type of kit, operator skills, external conditions setting up the reaction (temperature, humidity). It is possible to compare research results only if they were performed simultaneously, by the same operator and using kits from the same manufacturer.

The homogeneity of antibody titers can be assessed by the coefficient of variation (see Fig. 5). The diagram shows blood serum samples, which are distributed into groups: from 0 to 395, from 396 to 999, from 1000 to 1999, etc. It is conventionally accepted that for statistical reliable results when performing ELISA, it is necessary to select from 18 to 23 (18 minimum) blood serum samples. Information in the form of a diagram allows you to evaluate the arrangement of titers by group (most samples in one group or samples distributed in several groups) and in relation to the average value (heterogeneous or homogeneous titers). When studying the blood sera of day-old chicks (see Fig. 3), most antibody titers were located in one group and were close to the average value.

Good uniformity and high level MA indicates satisfactory condition the health of the parent stock and the correct vaccination program for chickens before laying using live and inactivated vaccines.

Many studies have noted a positive correlation between the virus neutralization reaction and the ELISA method. In addition, differences in mean titers between two groups of chickens vaccinated with different vaccines do not always indicate the immunogenicity of the vaccine. For example, the average antibody titer of 3000 in 25-day-old chickens immunized with vaccine A and 4500 in chickens vaccinated with vaccine B does not mean that immunization is better when using vaccine B. We can only say that chickens of both groups were successfully immunized. Differences in mean titer may be due to differences in kits or other conditions. The average titer value can be used to assess the quality of vaccination (bad or good), but not to compare different vaccines. With ELISA, the most significant criterion for assessing the results is the homogeneity of titers, which depends mainly on the quality of the vaccine, the conditions of its transportation and storage, and the technique of vaccinating chickens. To check the quality of vaccination, you can carry out additional research blood serum samples from 45-day-old chickens. In these studies, the average antibody titer in 45-day-old chickens was 3398 (Fig. 6) with a coefficient of variation of 23% (high homogeneity).

Infectious bursal disease, or Gumboro disease, is a common disease in chickens under four months of age. Manifests itself in the form of diarrhea, damage to the cloacal bursa, kidneys, gastrointestinal tract, intramuscular hemorrhages.

What is Gumboro disease in chickens, how to diagnose it and how to protect yourself from it– we invite you to talk in this article.

Gumboro disease: affects chickens and turkeys

Pathogen bursal disease is a virus of the Birnoviridae family that infects lymphoid cells, causing sharp decline bird immunity. The virus targets immature β-lymphocytes containing immunoglobulin M. There are two serotypes, roughly speaking, types, of this virus: 1 - affects only chickens, 2 - only turkeys. Moreover, the chicken Gumboro virus exists in several variations (subtypes).

Gumboro disease: how to get infected

Gumboro disease is highly contagious: up to 100% of birds of one group can get sick, and 40-60% die.

Methods of transmission of the pathogen Gumboro disease:

Infected birds; sparrows, pigeons, etc. can be carriers of the virus.

Feed, in particular – feed pests

At the same time, in a closed room, the avian bursal disease virus can live for up to three months, and in dirty rooms - in dust, uncleaned cages, and equipment - it can be stored for years. Not afraid sunlight, shows durability outside the room. In dry droppings it remains active for about two months, on the surface of glass and walls - about one month.

Gumboro disease: how it manifests itself

Externally, the chicken bursal disease virus appears already on the third day after entering the bird’s body. In general, a feature of the acute form of Gumboro disease (subacute course also occurs) is an unexpected, high incidence of poultry (40-100%), an acute peak in mortality (20-40%) and quick recovery in 4-7 days.

At the same time, the Gumboro virus most often occurs at the age of 6-8 weeks, and at 3-4 weeks.

It all starts with diarrhea, the droppings become watery, yellow-white. The chickens look depressed, huddled together, their feathers are ruffled, and their vents are dirty. The bird does not eat or drink. In this form, the disease manifests itself within 5-7 days, after which Gumboro disease is often complicated by manifestations of colibacillosis.

When the bird is opened, a cherry-colored cloacal bursa enlarged by 2-3 times is observed. Often blood clots may be visible in the cavity. There are hemorrhages under the skin on the chest, wings, thighs and in the glandular stomach.

Changes are observed in the bursa of Fabricius already on the third day: due to swelling and accumulation of secretions, it increases in size and becomes gray-yellow. On the fourth day of the disease, its weight almost doubles, hemorrhages, turbid contents and necrotic deposits are found in it. Sometimes intense hemorrhages are recorded, covering the entire bursa. On days 7-9, atrophy and fibrosis of the bursa are observed.

However, to finally put diagnosis of Gumboro disease in chickens is possible only on the basis of laboratory results.

Gumboro disease in chickens: prevention, vaccination, measures in case of a disease outbreak

In addition to observing hygienic rules for keeping poultry, chicken owners are obliged to regularly fight against virus carriers - chicken feather eaters, and monitor the quality of feed.

Chickens are vaccinated with Gumboro chicken virus vaccines in the event of a threat of disease outbreak. The following vaccines are used on the territory of Ukraine:

Inactivated vaccine from the BER-93 strain

Virus vaccines from strains UM-93 and VG-93

Gallivac IBD (France)

Inactivated vaccines N.D.V.+I.B.D+I.B. and quadractin N.D.V.+I.B.D+I.B.+Reo and NECTIVE FORTE (Israel).

There is no cure for Gumboro disease!

At diagnosing Gumboro disease in chickens a farm in which a disease is discovered is declared unfavorable and restrictions are introduced in accordance with the Instructions. Two months after removal, the birds are removed from the dysfunctional farm. Carry out complete disinfection of the farm. Farms in which IBD has not been observed for one year are considered free from chicken bursal disease.

Tatyana Kuzmenko, member of the editorial board, correspondent of the online publication "AtmAgro. Agro-industrial Bulletin"

Infectious bursal disease of chickens

Infectiosis Bursitis gallinarum (Gumboro disease) Acute viral disease chickens and turkeys, mainly 2-15 weeks of age, characterized by inflammation of the bursa of Fabricius, joints, intestines and internal hemorrhages.

HISTORICAL BACKGROUND- the disease was first recorded in 1956 in Gumboro County (USA). In 1962, Kostrov described Gumboro disease as a disease. Winterfeld and Hitchner (1962) isolated a virus from sick chickens that caused nephroso-nephritis in sick broilers. Therefore, sometimes this disease is called nephroso-nephritis. Later, Karnayup (1965) proved that the symptoms of nephroso-nephritis are concomitant, the main and permanent changes are found in the bursa of Fabricius, which is why the disease began to be called infectious bursitis.

The disease is widespread in many countries of America, Europe, and Asia, where industrial poultry farming is developed. Data from serological studies show that the infection rate of herds ranges from 2 to 100%. And the reason for this is considered to be the constant import of poultry.

PATIENT- RNA virus from the genus Aviovirus of the Reoviredae (reovirus) family. The virion size is 70-75 nm. When 9-day-old embryos are infected in the yolk sac, the virus causes their death after 6 days. In addition to growth retardation, it causes

the appearance of edema, necrotizing lesions in the liver, which are typical for all viruses of this group. 3 days after the introduction of virus-containing material into the fibricium bursa, changes characteristic of a natural infection occur. In chicken embryo fibroblast culture, the virus causes a cytopathic effect. Virus-neutralizing and precipitating antibodies are formed in recovered birds.

RESISTANCE - the virus is resistant to ether, chloramine and pH 2.0, sensitive to trypsin. Indoors, the virus persists in droppings for 52 days. At 56°C it does not die within an hour. A solution of chloramine (0.5%) inactivates the virus in 10 minutes, formaldehyde (0.5%) in 6 hours.

EPISOOTOLOGICAL DATA- chickens of all ages are susceptible to the pathogen, but especially broilers aged 2-15 weeks. The most sensitive are 3-6 week old White Leghorn chickens. In adult chickens the disease is asymptomatic.

The source of the infectious agent is sick chickens that shed the virus in their droppings.

Infectious bursitis is an extremely contagious disease that is easily transmitted when birds are housed in close quarters. Chickens become infected through contaminated feed and water. A vertical route of transmission of the virus through infected eggs cannot be ruled out. Infected care items, equipment, clothing, and personnel play a certain role in the transmission of the pathogen.

The possibility of the virus spreading through the air has been proven. The reservoir of the pathogen can be flour beetles.

In fresh epizootic foci, the disease is acute and subacute, and in stationary outbreaks it is chronic and asymptomatic. In a number of farms, an immunizing subinfection is mainly recorded among birds.

PATHOGENESIS- consists of damage to lymphoid tissues, and first of all, lymphocytes of the bursa of Fabricius, spleen, and caecal glands of the blind processes are destroyed. The virus enters through digestive tract and after 24-48 hours it is localized in the bursa of Fabricius, affecting B lymphocytes.

CLINICAL SIGNS- incubation period 1-2 days. Occurs in chickens under 3 weeks of age in the form of immunosuppression, which is manifested by increased sensitivity to bacterial infections.

It can occur in an acute form in the first 5-7 days after the disease in chickens aged 3 to 6 weeks. In case of low poultry resistance, mortality can reach 90%.

One of the first signs is diarrhea, with the release of yellow, liquefied droppings, or mucous-watery, white droppings; feathering is impaired.

Then there is sudden apathy, trembling, signs of damage to the nervous system. The bird soon loses the ability to move and dies in a state of prostration.

Maximum mortality for 3-4 days from the beginning of the disease outbreak,

then the mortality rate decreases.

When the disease lasts 6-8 days, morbidity is 10-20% of birds, mortality is 1-15%.

Hematological changes are characterized by lymphopenia and erythrocytosis. Over 2 days of illness, the total number of leukocytes decreases, on the 5th day it increases and reaches a maximum on the 7th day after infection.

PATHOLOGANATOMICALCHANGES- the corpses are well-fed, but the muscles are dehydrated and pale, the goiter is empty, multiple pinpoint and striped hemorrhages are revealed, especially often under the skin of the thigh; the muscles are dark purple.

The bursa of Fabricius is greatly increased in volume, more than 2 times, and contains gelatin-like transudate; there are fibrinous deposits in the folds of the bursa, and in severe cases there is bloody fluid.

Swelling of the liver, necrotic foci, and atrophy of the spleen are noted. The pancreas is changed, nephrosis. In the final stage of the disease, swelling of the kidneys and atrophy of the bursa of Fabricius appear. Partial banded hemorrhages in degenerated skeletal muscle of the myocardium, serous membranes, glandular stomach and intestines.

The most typical histological changes are necrosis

lymphoid elements of the bursa of Fabricius, thymus, spleen, renal degeneration.

DIAGNOSIS- infectious bursitis is a difficult to detect infection that spreads unnoticed, is masked by other diseases and physiological disorders, and only with a typical course is it relatively easily diagnosed based on clinical and pathological signs. They take into account the high percentage of morbidity, rapid spread and relapse within 5-7 days. The diagnosis can be confirmed by the detection of characteristic changes in the bursa of Fabricius.

For the final diagnosis, histological studies are carried out and a bioassay is performed by infecting 9-day-old chicken embryos on the chorioallantoic membrane. Embryos die within 3-5 days after infection.

The virus is identified in RN, RDP and ELISA.

DIFFERENTIAL DIAGNOSIS- exclude coccidiosis, poisoning, infectious bronchitis, hemorrhagic syndrome, mycoses, Newcastle disease.

TREATMENT- not developed.

IMMUNITY- use live and inactivated vaccines of the BG strain (Gumboro disease), IBD (infectious bursal disease), Winterfield-2512.

The first vaccine is administered twice at the age of 7-21 days with an interval of 10-14 days using the drinking method. Second time at the age of 110-120 days

once intramuscularly into the pectoral muscle area or into the thigh in a volume of 0.5 ml. Immunity occurs 14-21 days after vaccination and lasts up to a year.

In foreign practice, a vaccine made from a weakened strain of the virus is used with drinking water and aerosolized. infectious bursitis. Among foreign vaccines, you can use Nobilis Gumboro D78 and 228E. An inactivated vaccine, Nobilis Gumboro inc., has also been developed.

PREVENTION AND CONTROL MEASURES- carry out general veterinary and sanitary measures to prevent the introduction of the pathogen into the farm.

The young animals of each technological batch are raised in isolation. The state of poultry resistance is controlled through targeted feeding and maintenance.

The air entering the poultry house is cleaned with filters and disinfected with ultraviolet rays.

When infectious bursitis appears, restrictions are imposed. Sick and suspicious birds are destroyed. Healthy people are vaccinated.

The premises are thoroughly disinfected with solutions of caustic soda, bleach (2-3%), and an aerosol of iodide preparations.

If the disease cannot be controlled by general veterinary and sanitary measures, the farm stops incubating eggs and carries out additional health measures.

There are no deadlines for lifting the restrictions; they are set by veterinarians, since it is difficult to get rid of this disease due to the rapid development of this disease as a stationary one.

G.V. Beginin, chief veterinarian PF "Gayskaya"

The epizootic and economic well-being of poultry enterprises largely depends on timely diagnosis and measures specific prevention against infectious diseases, which include Gumboro disease.

Gumboro disease at the Gayskaya poultry farm in the Orenburg region was first registered in November 1995 among 45-day-old chickens of the Zarya-17 cross. Clinically, the chickens were observed to be lethargic, lack of appetite and watery diarrhea. Characterized by ruffled plumage and at times muscle tremors.

During the epizootic period, the disease manifested itself in 6 workshops of the poultry farm. The disease was observed simultaneously in different poultry houses and the number of sick chickens in some poultry houses reached 50%, and in others – 10–20%. Chicken mortality in some workshops was more than 30% within 7–10 days. The maximum death of birds was noted on the 3rd–5th day of illness and decreased in the next 4–5 days.

At autopsy, dryness was noted subcutaneous tissue, pinpoint or diffuse hemorrhages in the pectoral and femoral muscles, the bursa of Fabrice was enlarged 2–3 times, hyperemic or with hemorrhages (in 30–40% of cases), sometimes there were fibrin deposits in its cavity. Kidney lesions were noted in 40% of the examined corpses.

They were enlarged, with hemorrhages, and there was an accumulation of urates in the ureters. The diagnosis was made on the basis of epidemiological data, clinical signs, pathological changes and the results laboratory research, held at VNIVIP.

Since the outbreak of Gumboro disease, different vaccines have been tested at the poultry farm, varying in their effectiveness due to the presence of maternal antibodies and changes in poultry crosses.

Initially, against the background of low passive immunity, the double use of the vaccine from the “VNIVIP” strain made it possible to ensure high safety and productivity of poultry in unfavorable conditions. After a long period of successful prevention, clinical signs and lesions in the bursa of Fabricius during autopsy of dead birds appeared in the vaccinated flock after reaching 35–37 days. Then the disease spread to other buildings where birds of an age susceptible to the IBD virus were kept.

An analysis of the reasons for the failure of vaccine prophylaxis showed that by that time the young animals accepted for rearing had high levels of maternal immunity, since they were obtained from hyperimmunized laying hens, and in the batch of chickens where a specific death was observed, there were violations of the vaccine application technique, in some In some cases, the poultry house housed chickens of different ages with different immune backgrounds.

It was possible to stabilize the epizootic situation on the farm with the help of a vaccine from the BG strain. With the transition to a new vaccine clinical manifestation diseases were not observed, but we encountered such problems as atrophy of the bursae of Fabricius, retardation of poultry in growth and development, a high percentage of their rejection, a low percentage of commercial pullets and kidney pathology in replacement young stock caused by increased content uric acid salts in the ureters.

After changing the poultry population to the Rhodonit cross, in which the parent flock was not vaccinated with the inactivated Gumboro vaccine and the level of maternal antibodies in the RDP of day-old young animals did not exceed 30%, they began to use a vaccine from the KBK strain produced by Biovet LLC (St. Petersburg ). The vaccine was administered once into the upper third of the neck of day-old chickens subcutaneously in a volume of 0.2 ml. To dilute the vaccine, we used Marek's disease vaccine diluent produced by the Kursk Biofactory.

The effectiveness of the vaccine from the KBK strain was assessed by the level of specific antibodies in the RDP, bursal index and titers to the Newcastle disease virus.

In the blood serum of vaccinated chickens 25–30 days of age positive reaction in RDP was noted in 80–100% of cases. The bursal index at the age of 30 and 40 days was at least 3.5. The bag had a natural color and without visible signs defeats. Group immunity against Newcastle disease 15 days after revaccination was 6.42 log2, which indicates a pronounced immunological reaction of the bird to the vaccine. Observations have shown that the vaccine from the KBK strain does not cause immunosuppression; the growth and development of poultry complied with zootechnical standards. Safety among young animals during the period of use of this vaccine increased by 5%, the yield of commercial pullets was 97% with high uniformity of the herd.

Some batches of chickens were vaccinated against Marek's disease and Gumboro disease simultaneously. Performance indicators for separate and joint immunization against Marek's and Gumboro's diseases did not differ significantly.

In 1998, another change of livestock was carried out to the “Loman White” cross, where the prevention of Gumboro disease was carried out according to the program of the “Loman” company (Germany) and passive immunity in the first days of life, according to ELISA data, was 1: 5000 and higher. In the current situation, it was necessary to change the vaccine and adjust the existing disease prevention program.

Taking into account previous experience in disease prevention and positive reviews colleagues on the prevention of Gumboro disease using an inactivated vaccine on young birds, it was decided to vaccinate with this vaccine from the “52/70 M” strain (produced by Biovet LLC). At the same time, a comparison was made with a live vaccine from the “BG” strain and a scheme for using the killed vaccine was worked out to develop tactics for preventing the disease in the future.

To do this, one group of chickens was vaccinated with an inactivated vaccine at 10 days according to the instructions for using the drug; the second group was vaccinated at 16 days with an inactivated vaccine; the third and fourth groups of chickens were simultaneously vaccinated with inactivated and vaccine from the “KBK” strain at 10 and 16 days, respectively; chickens of the fifth group were vaccinated with a vaccine from the “BG” strain at 7 and 17 days.

The effectiveness of vaccines and schemes for their use was judged by the well-being of the farm against Gumboro disease, general safety, productivity, business output of replacement young animals and by the results of blood serum studies for the presence of specific antibodies in the RDP of 30-, 40-, 50- and 60-day-old chickens. At the same time, we studied the level of post-vaccination immunity against Newcastle disease, and also determined the bursal index in different terms poultry rearing.

Comparative production indicators for raising poultry according to the specified vaccination schemes are given in Table No. 1.

Table 1
Performance indicators of chickens vaccinated with different vaccines against IBD

From the presented data it is clear that the vaccines used against Gumboro disease according to the indicated schemes provide complete protection of chickens from the field virus. Administration of inactivated vaccine to chickens does not cause adverse reactions local and general. Chickens vaccinated with an inactivated vaccine at different times separately and in association with a live vaccine have the highest safety rates (up to 99.4%), average daily weight gain that meet regulatory requirements, a high percentage of commercial pullet yield (97.4%), low rejection percentage (0.49%) and high uniformity of the herd (88.3%).

The dynamics of serological indicators of the reaction to the introduction of vaccines indicates that the most active group immunity was established in group IV of chickens simultaneously vaccinated live and inactivated by vaccines at 16 days. The arithmetic mean titer of serum in the RDP was 3.8 log2. High performance bursal index (more than 5.2) were noted in I -IV groups, while in the V group low performance bursal index was observed starting from 30 days of age.

CONCLUSION
The effectiveness of preventing Gumboro disease is closely related to the type of vaccine, compliance with the rules for its use, and the presence of maternal antibodies, which negatively affect the development of post-vaccination immunity, both when administered live and inactivated vaccines.

The vaccine from the KBK strain is effective against a low immune background of passive antibodies. The use of a vaccine from the “BG” strain helps stop the infection, but causes damage to the bursa and kidneys, which leads to a decrease in the overall safety and productivity of the bird.

High safety and productivity in our farm conditions was achieved with joint vaccination with inactivated and live vaccines against IBD at 16–18 days.

Prepared based on the materials of the “Vth International Veterinary Congress on Poultry Farming” for the website