Diagnosis and Prevention of Infectious Bursal Disease
Infectious bursal disease (IBD) is an acute highly contactable infectious disease caused by infectious bursal disease virus (IBDV). The disease is characterized by a high incidence (up to 80% to 100%), a short duration ("one-off type"), and a typical spike-like death curve. The disease can induce or inherit Newcastle disease, Marek's disease, infectious bronchitis, E. coli disease, salmonellosis, staphylococcal disease and other diseases, and bring huge economic losses to the chicken industry. Many experts and scholars have made a lot of researches and reports on IBD and played an extremely important role in guiding the prevention and treatment of this disease. In recent years, the author has conducted in-depth studies on the local epidemic characteristics of the disease and accumulated certain experience in the diagnosis and control of infectious bursal disease. The following is a brief discussion on the diagnosis and prevention of IBD.
1 Clinical symptoms
The diseased chickens are characterized by mental depression, drowsiness, loose feathers, diarrhea, anorexia, cold-wracking, drainage-like white, yellow, and green fecal matter. The faeces often adhere to the anus; diseased chickens often stand upright, and some fall to the ground. Overdue course, the peak of death is concentrated in the 5th to 7th days after infection. Diarrhoea is an important feature. When some chickens in the flock appear lassitude, the litter is quickly wet, and the chickens lick each other, indicating that the disease has occurred. 3 to 6 weeks old chicks are most susceptible to infection.
2 pathological changes
(1) Muscle Hemorrhage: The necropsy of the dead chickens revealed that the lateral muscles of the thighs and the pectoral muscles were a bit like and patchy. (2) Typical lesions of the bursa: swelling, bleeding, degeneration, jelly-like edema, or cheese-like exudates, and a longer duration of the disease. (3) Kidney swelling, tubular and ureter filled with white urate. (4) Gastrointestinal hemorrhage in individual cases, bleeding zone at the junction of glandular stomach and muscle stomach.
3 laboratory diagnosis
The disease can be diagnosed through clinical symptoms and pathological necropsy. The diagnosis should be made in the laboratory. The condition can be passed through the agar diffusion test (AGP).
4 Prevention and treatment
4.1 To prevent and control the disease, on the one hand, it is necessary to strengthen environmental control, reduce the number of virulent poisons in chicken coops, and reduce the threat to chickens; on the other hand, it is necessary to strengthen feeding and management, reduce stress, and appropriately increase the temperature of brooding and reduce the risk. The content of protein and salt in the feed is added with multivitamins, etc. The chicken is then vaccinated to give the chicken a strong immunity against infectious bursal disease. There are many kinds of vaccines for the prevention of this disease. The immunization procedure differs depending on the breed, source, and different chicken farms. Conditioned chicken farms can develop immunization programs by monitoring maternal antibody levels in chicks. Chicks with no maternal antibodies can be immunized for the first time with a low-toxic infectious bursal disease vaccine at 7 to 10 days of age, and boosted with a moderately virulent vaccine at 1 to 2 weeks; for maternal antibodies. The chicks were first exempted from the medium-disease vaccine around the age of 2 weeks, and boosted once every 7 to 10 days. This produced a good immune response.
4.2 The treatment of this disease is generally the use of infectious bursal disease yolk antibody or hyperimmune serum intramuscular injection, dose 1 ~ 2ml / plume, can control the death in a timely manner, especially the timely application of the disease in time, the effect is obvious. For example, when chickens have just started to have symptoms of infectious bursal disease, attenuated vaccines can be used for emergency immunization with 3 to 4 times the dose of drinking water, and all can receive good results. In addition, it is necessary to strengthen the feeding and management, and add symptomatic treatment of detoxification of kidney swelling to the drinking water, add a quick-improving stress king to relieve stress, and add ciprofloxacin lactate to prevent secondary bacterial infections.
5 Experience and discussion
5.1 Causes of the Epidemic According to the local epidemic data analysis of the disease, the prevalence of Infectious Bursal Disease in chickens in Kaiping and Taishan is about 25%. The author believes that the main reasons are: (1) farmers do not pay attention to do a good job of environmental sanitation and disinfection work, production areas, living areas without strict separation; chicken dealers enter the arena without disinfection, resulting in the introduction and spread of pathogens. (2) Unreasonable immunization procedures: Maternal antibody levels in chick populations are uneven, and there are significant differences among groups. In the absence of immunological monitoring equipment for maternal antibody levels, it cannot be based on maternal antibodies. Determine the first free time, resulting in immunization too late or too early to achieve a good immune effect. (3) Improper use of vaccines: When immunizing with drinking water, some farmers did not add skimmed milk powder when diluting the attenuated vaccine, or used tap water containing chlorine ions and other disinfectants to reduce the vaccine potency. (4) Super strong strains exist in chicken farms.
5.2 Prevention of the disease should be selected suitable vaccine and dose of domestic IBD vaccine, mainly IBD attenuated lyophilized vaccine, IBD attenuated vaccine and IBD inactivated vaccine 3 kinds. The author believes: (1) According to the local prevalence of different strains to select the corresponding strain vaccine. (2) Appropriately increase the dose of immunization: Under normal circumstances, one dose should be used for immunization in strict accordance with the instructions, but the first immunization dose or in the epidemic should be doubling the amount of immunization.
5.3 Select the appropriate route and method of immunization IBD vaccines can use drinking water, nasal drops method. Due to the simplicity of drinking water immunization, many professional households (fields) like to use it. If drinking water is used for immunization, the chickens should be stopped according to the season and temperature before immunization. Generally, water should be stopped for 1 to 3 hours in the summer and 2 to 4 hours in the winter. In the hot summer, it is best to use the vaccine in the morning or evening. In order to avoid the impact of sun exposure on the vaccine price; the vaccine water is best to use distilled water or special diluent, ban the use of water containing chloride ions, disinfectants and other drugs; in the preparation of attenuated vaccines, the diluent should be added 0.2% skim Milk powder or 2% skimmed milk is used for protection; in order to ensure that each chicken can drink enough doses of vaccine, it is required to place more drinking fountains and drink in 30 minutes.
5.4 Strengthen Feeding Management and Prevent IBD In addition to doing a good job of immunization, it is also necessary to pay attention to environmental sanitation and disinfection, control the rearing density, and avoid stress as much as possible. In normal times, it is necessary to strengthen the management of feeding, regular cleaning of excrement and sewage, and it is forbidden for outsiders and vehicles. When entering a chicken farm, it is necessary to enter it strictly before being allowed to enter.
5.5 Comprehensive treatment Once the epidemic occurs, injection of high-immune egg yolk should be taken or emergency vaccination should be performed. Kidney swelling antidotes and antibiotics should be added to drinking water to relieve symptoms and prevent the concurrent occurrence of other infectious diseases. The high-immunity egg yolk liquid is used only for emergency treatment and cannot be used for prevention. The use of high-immunity egg yolk is a kind of passive immunity. The protection time is very short and can not play an effective immune function. Besides, the complex composition of egg yolk is indispensable to other pathogenic pathogens. Causes some diseases to spread, there may also be other disease antibodies, interfere with the immunity of some vaccines and lead to the prevention of other diseases.
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