Infectious bursal disease in chickens is a severe, immunosuppressive, high-exposure infectious disease caused by infectious bursal virus. Since the discovery of this disease in Guangzhou, China in 1979, it has been severe and has a high mortality rate for a considerable period of time. In recent years, the incidence of this disease has decreased a lot, but during this period of time, the incidence of the disease has been serious in central China, northeast China and other regions, bringing losses to local farmers.
Direct harm: chickens infected with chickens die, weight gain decreases, feed utilization rate decreases, production performance declines, resulting in serious direct economic losses;
Indirect harm: causes severe immunosuppression, inhibits the production of vaccine immune antibodies, increases the susceptibility of diseased chickens to other pathogens, and induces the occurrence of other diseases.
1. Bursal disease is highly contagious and spreads quickly, and once the chickens become ill, they quickly affect the whole group or the whole field; if there is no secondary infection, the mortality rate is relatively low and there is almost no obvious peak of death.
2. In recent years, there is no obvious seasonality, which can occur all year round.
3. Bursal disease is a highly direct contact infectious disease, and the virus has a high degree of tolerance, which can exist in the environment of the chicken coop for a long time and is not easy to remove.
1. In recent years, the clinical and autopsy symptoms of infectious bursal disease are not typical in most areas, and the symptoms in some areas are more typical, and there are more mixed infections;
2. It is usually manifested that most of the food intake does not rise for several consecutive days, and some have decreased slightly;
3, the chicken is not in good spirits, draining yellow and white thin feces;
Drain yellowish white thin feces
4. Most of the autopsy shows slight yellow jelly gelatinous edema of the bursa, some have no external yellow jelly gelatin edema, only mucus in the bursa, and there are bleeding spots in the mucous membrane;
5. The surface of the liver has yellow stripes, and the edges often show necrosis changes in earth yellow;
The liver is earthy yellow
6. Kidney enlargement and bleeding, urate deposition;
Kidney swelling and bleeding
7. Some have hemorrhagic spots in the leg muscles and pectoral muscles; some have air cystitis and perihepatitis.
Purple on the wing joints, bruised and bleeding
Relying solely on vaccine immunization cannot effectively prevent pure bursal disease, and it is necessary to carry out comprehensive prevention and control, such as choosing the right vaccine, the right timing of immunization, and strengthening biosecurity and scientific feeding management, the specific measures are as follows:
1. Establish a systematic breeding system
Pay attention to biosecurity measures, do not let people enter the chicken farm at will in the early stage of brooding, and avoid bringing the virus into the chicken coop through the clothing of the personnel;
Implement the "all in, all out" breeding system, as far as possible to create a suitable small environment for the chickens, reduce stress.
2. Strengthen disinfection
For the high-intensity tolerance of bursal disease for the natural environment, if strict and thorough cleaning and disinfection is not taken, a large number of infectious bursal viruses in the chicken coop can break through the maternal antibody than vaccine strains, causing bursal disease, so we must pay attention to the disinfection of the chicken farm environment, the specific steps are as follows:
For the chicken coop to be thoroughly cleaned, and the foam cleaning agent (Double Liqing) should be used for cleaning, so as to ensure that the cleaning is as clean as possible;
Disinfect the floor and walls with 3-5% hot alkali after cleaning (avoid spraying on iron equipment);
Spray disinfection of the chicken coop with iodine preparations (halogen elements) after one day apart, followed by fumigation with formalin for more than 12 hours;
Finally, after the chicken coop is heated up, it is disinfected with disinfectant (new OF) spray once more 2 days before entering the chicken.
3. Strengthen the immunization of breeders and egg disinfection
Immunization is the main method of controlling infectious bursal disease in chickens, especially the immunization of breeding flocks, passing their maternal antibodies to offspring to protect chicks from early infection with bursal disease virus.
Therefore, at the age of 18-22 weeks and 40-45 weeks of age of the breeders, they are each immunized once with a high-quality bursal inactivated vaccine (Xinfakang);
A bursal inactivated vaccine is also injected once during forced moulting of breeders, thus ensuring a high maternal antibody to commercial broilers;
At the same time, the disinfection of eggs is strengthened to reduce the invasion of pathogens.
4. Improve the body's resistance and avoid the invasion of viruses
Before the vaccine produces effective antibody protection (15-25 days), astragalus polysaccharide (Kanglineng) + transfer factor (pan-easy-flat) is used for prophylaxis.
5. Reasonable immunization procedures for commercial broiler chickens
If the b87 strain, mb strain, 2512 strain and other vaccines cannot be effectively protected, the new method of injecting the new method of binary oil seedlings (Xinfakang) can be used at the same time as immunizing lyophilized seedlings to improve the protection rate of commercial broiler chickens for bursal disease in high-incidence areas;
Moreover, adding drugs that improve the body's immunity - transfer factors for 3-5 days before and after immunization can not only reduce immune stress, but also improve the body's immune capacity.
6. Medication
If bursal disease is not serious and the death is not high, antiviral drugs such as astragalus polysaccharides can be added for drinking water treatment, and drinking water at night to take liver protection and kidney protection (liver and kidney treasure) to reduce the damage of the disease to the liver and kidneys.
If the death is too high, but there is no secondary infection, you can urgently inject bursal refined yolk antibodies in the early stage of the disease, and antibiotics such as kanamycin sulfate, enrofloxacin, and cefotafurofuran sodium can be added to the antibodies to reduce the secondary infection of bacteria.
If death is high, and there are other diseases such as pericarditis secondary to injection of high-quality antibodies, it is also necessary to choose excellent antibiotics (florfenicol, linke grandeurmycin) and cooperate with Ruiwo Xingankang (Qing plague detoxification oral solution) or Shuanghuanglian oral liquid (Golden Kang) for treatment.
At the same time, timely collection of disease materials from sick chickens and identification and classification of viruses provide a basis for further effective prevention and control measures.
1. There are differences between different strains of infectious bursal disease and different types of vaccines
Commonly used infectious bursal vaccines in China are b87 strains, mb strains, 2512 strains, v877 strains, etc., and there are differences between different vaccine viruses and protective capacity.
Weakly toxic seedlings: the use has certain risks, there is a possibility of horizontal or vertical transmission; especially the weakened strains are back to virulence, resulting in disease outbreaks. Under the influence of maternal antibodies, the early use of the weakened vaccine is ineffective, and the cross-protection ability of the ibdv super strong strain is not strong.
Genetically engineered subunit vaccines: safe, but low immunogenicity and poor cellular immunity by expressing the vp2 protein of infectious bursal virus compared to whole viruses.
2. The immunized flock has a weak resistance to strong poisonous attacks
In some areas, the wild poison of the farn's sac is seriously polluted, the chicken coop is polluted by the infectious farnocyst strong poison, and the poisoning force freeze-dried seedlings cannot resist the invasion of strong poison.
Some researchers have experimented to show that the virulence of infectious bursitis wild strains varies greatly. The most pathogenic gx8/99 caused a mortality rate of 70-92% in SPF chickens, but the mortality rate of Spf chickens vaccinated with yn2/99 strains was almost zero. The lethality rate of the rest of the strains to SPF chickens ranged from 6 to 77%, and there were differences in antigenicity and pathogenicity between the serotypes of the strains.
When the elected vaccine does not match the genotype of the virus being invaded, or when the virus is more virulent, the immunized chickens are also at risk of infection.
3. Improper timing of immunization causes immunosuppression
Domestic virulence is widely used in the strong lyophilized bursay, while the immunization of infectious bursal disease is getting earlier and earlier, causing damage to the bursal, causing immunosuppression, and at the same time, vaccine immunization is improper, vaccines interfere with each other; or there are other immunosuppressive diseases.
4. Improper immunization program of breeders
Some parent chicken farms do not carry out bursal inactivated vaccine immunization at about 40 weeks of age, and some parent breeder farms do not carry out bursal disease vaccine immunization after mandatory moulting, in which case the maternal antibody level gradually fades, or is not neat, and even the commercial generation has almost no maternal antibody epidemic prevention, and there is an immunization gap period.
5. The maternal antibodies of chicks are uneven
Some enterprises use different days of age, different breeding farms to provide eggs for incubation, different breeders due to different factors such as different immunization time and procedures for bursal disease, different groups of infectious bursal disease antibodies are not the same, which may cause chicks infectious bursal disease antibodies are uneven.
Infectious bursitis is serious and requires us to detect it early, treat it in a timely manner, select a reasonable immunization program, formulate a correct prevention and control plan, and deal with the harm caused by infectious bursitis in recent years.
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