How to prevent chicken kidney-type infectious bronchitis

Renal infectious bronchitis is a pathological manifestation of infectious bronchitis. China first reported in 1972 by Rong Ronglu that infectious bronchitis existed in Guangdong Province, and the majority of the provinces subsequently reported the disease. Infectious bronchitis that occurred during this period was mainly respiratory type. In 1962, Winterfied et al. discovered nephropathogenic infectious bronchitis virus in the United States and named it Holte strain. Representative strains of this type include Holte strain, Gray strain, CV56b strain, Wolgemuth strain, etc. Among them, Gray strain is Mitigation strains. In the same year, Cumming isolated N1/62 (T-strain) in Australia, which is considered to be a representative strain of the nephropathogenic infectious bronchitis virus. Since the 1990s, kidney-type infectious bronchitis has also erupted in China, and the epidemic has been widespread. Especially in recent years, kidney-type infectious bronchitis has become widespread in China's broiler flocks and has caused serious losses for chicken production.

First, the pathogen

Infectious bronchitis virus (IBV) is a member of the Coronaviridae coronavirus, enveloped, single-stranded positive-stranded RNA virus. The virus particle morphology is polymorphic, but most are spherical and approximately 80 in diameter. At -120 nm, the capsular surface was loosely and evenly arranged with coronal fibers, like a crown. The fibers were less dense than the rod-shaped fibers of the paramyxovirus and some of the strains lost more than 100,000 grams when the fiber was lost. Infectious bronchitis virus can grow in 10- to 11-day-old chicken embryos. The chicken embryos are initially inoculated with natural toxins. Most chicken embryos survive, but the virulence of chicken embryos increases with the number of subcultures. On the day of the inoculation, 80% of chicken embryos died on the 9th day after inoculation. The characteristic changes of the embryo body are developmental obstruction, the embryo body is rolled into a spherical shape, the foot deformation is pressed on the head, the amniotic membrane is thickened, closely adheres to the embryo body, the yolk sac is reduced, the allantoic fluid is increased, and the renal uric acid salt is deposited. Infectious bronchitis virus can also grow on 15- to 18-day-old chick embryo kidney cells (CEK), chicken kidney cells (CK) and chicken embryonic liver cells (CEL) after multiple passages (6-10 generations) Can cause more obvious cytopathy, showing cytoplasmic fusion, the formation of syncytia and cell death. The virus was inactivated at 56°C for 15 minutes or at 45°C for 90 minutes and was sensitive to diethyl ether. 50% chloroform was used for 10 minutes at room temperature and 0.1% sodium deoxycholate at 4°C for 18 hours allowed the virus to completely lose its infectivity. The virus is sensitive to common disinfectants, and it can be inactivated by 1% of a solution of sulphate, 1% of formalin, 2% of sodium hydroxide and 70% of ethanol for 3 to 5 minutes.

Second, popular features

The main mode of transmission of the disease is diseased chickens that discharge the virus from the respiratory tract and transmit it to susceptible chickens through airborne droplets. In addition, through contaminated feed, drinking water, utensils, etc., can also be infected through the digestive tract. It can be affected all year round. Insufficiency of nutrition, high density, low temperature, sudden climate change, cold, poor ventilation, or stress can induce the disease. All ages of chickens can be affected, but the most serious hazard to chicks, laying eggs before the 15th day of infection will cause life-long fallopian tube damage, laying hens mature adult hens, fallopian tube cysts, chicken life is not eggs . The incidence of roosters is often higher than that of hens. The incidence of broilers is higher than that of laying hens. This may be related to the growth rate of chickens and the protein content in feed. The higher the protein content in feed, the faster the chicken grows and the more the chickens die. The higher the rate.

Third, clinical symptoms

The onset age of renal infectious bronchitis is mostly concentrated in 2-8 weeks of age. The typical symptoms of this disease are biphasic. The first phase has short-term (about 1 to 4 days) mild respiratory symptoms, including ???(1)缣纭 . . 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭 缣纭The basics of benzene cone gangrene? cone consolation? dead vomiting wild purple? 啵 笄 笄 笄 笄 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 靶 . . . . . . ..致 Shake (9) 阉 ( ( ( ( ( ( ( (4) 硭ソ 2 20 20 days, the mortality rate as high as 15% to 40%; laying hens will also cause decreased egg production, abnormal production of eggs and dead embryo rate increased, But not much death.

Fourth, pathological changes and diagnosis

Chicken feet were dry, mucus was found in the nasal cavity, and edema in the throat, trachea, and bronchial mucosa thickened. Mild bleeding was seen, and some of the lower 1/3 of the trachea had mucus plugging. Serious dehydration, muscle cyanosis, skin and muscle are not easy to separate. The kidneys are highly swollen and pale, and the renal tubules and ureters are thickened. The white uric acid salts are filled with white uric acid, commonly known as "Plasma kidney". Severe cases have white frost-like deposits on the surface of the pericardium, liver and intestines. Cloaca is filled with white lime-like dilute feces; longer duration, secondary E. coli and mycoplasma infection, the formation of bronchitis, hepatic inflammation and other sepsis changes.

According to the epidemic characteristics of the disease, clinical symptoms and pathological necropsy, a preliminary diagnosis can be made. Diagnosis requires a series of laboratory tests such as virology, serology, and molecular biology.

V. Immunological control

Vaccine selection Due to the complex serotypes of the infectious bronchitis virus and the weak cross-protection between them, new serotypes and variant strains continue to emerge, and clinical protection against renal infectious bronchitis is well established in certain regions. The vaccine may not have protective effects on renal infectious bronchitis in another region. If the blind introduction of a vaccine against nephropathogenic bronchitis in foreign countries may have a protective effect on local renal infectious bronchitis, or it may not be completely protected, it will add new strains to the local community. Therefore, before the vaccine is used, it is necessary to grasp the serotype of the virus that is prevalent in the local area, and use a vaccine strain that is consistent with the antigenicity of the local epidemic strain, so as to achieve effective immune prevention. Currently used vaccines include: H120 strain, H52 strain, Ma5 strain, M41, 28/86 strain, 4/91 strain and so on.

H120 strain, H52 strain, Ma5 strain, and M41 belong to the Massachusetts strain. H120 and H52 are the Netherlands strains introduced in China. They have good immune effects on most of the serotypes of infectious bronchitis virus in China and some of them are kidneys. The diseased strains also have certain cross-immunity, so they have become the two most widely used strains in China; the H120 strain vaccine is very weak, very safe and can be used for broiler chickens and laying hens over 1 day of age; H52 strain virulence Stronger, generally not used in chicks and laying hens in production practice, mainly used for chickens from 60 to 120 days of age; Ma5 toxicity is equivalent to or lower than H120 strain, which can be used for chicks or for production. Laying hens; M41 has a strong virulence, and the strains isolated from many countries and regions belong to the same serotype as M41, so M41 is widely used in the production of inactivated vaccines.

A 28-86 strain was isolated from a 28-kilo strain isolated from No. 28 house in the kidney-type infectious bronchitis chicken farm in Poxi Valley, Italy, in 1986. This strain is considered to be one of the most virulent strains of nephrotoxic lesions. After passaging on SPF chick embryos, it achieved a satisfactory level of virulence but still retained a good immunogenicity. Through a series of flock regression tests, it was demonstrated that 28/86 strains were weak and stable, their virulence did not return strongly, they had good immunogenicity and high safety against immune animals, and they were able to effectively resist kidney-type infectious bronchitis. Virulent attack. This strain has low toxicity and can be used in chickens of any age. It has a high protection rate for kidney disease and a stable virulence. 4/91 strains are used to prevent chickens from deep muscle disease, decrease egg production rate, and have respiratory tract. A variant communicable bronchitis strain with symptoms and diarrhea. In the past two years, 4/91 strains of vaccines have been used in the immunoprophylaxis of renal infectious bronchitis in some regions and have been found to have better preventive effects.

Precautions for Use The live vaccine is best prepared by immunization with intranasal or eye drops, which is beneficial to the production of local antibodies. During the immunization operation, it should be noted that the infectious bronchitis virus attenuates rapidly in water and the vaccine must be dripped within 30 minutes after dilution. Since the infectious bronchitis virus rapidly rises in the water and causes unevenness, it must be shaken at any time during use. When immunizing with a single vaccine or a new double live vaccine, do not mix the two vaccines together for immunization, because excessive amounts of the infectious bronchitis virus will interfere with Newcastle disease's immune response. If single seedlings are used for immunization, they should generally be vaccinated for 1 to 2 weeks after the immunization against Newcastle disease or with Newcastle disease and infectious bronchitis combined live vaccine (new branch) in order to avoid interference. The new double live vaccine is produced according to a scientific and reasonable ratio and can effectively eliminate the interference between the two viruses.

The establishment of immunization procedures When developing immunization procedures, it should be determined according to the prevalence of the disease in the local area, feeding and management conditions, the characteristics of vaccine strains, the level of maternal antibodies in the flock, etc., so that appropriate immunization time can be selected and vaccines can be effectively used. Protection. The loss caused by this disease is mainly in the young stage, and the maternal antibody can not stop the infection but only alleviate the symptoms of the disease. So chick immunization is the focus.

The first day of childbirth is dependent on the level of maternal antibody of the chicks, the method of immunization, and the local incidence. In the high incidence area of ​​kidney-type infectious bronchitis, the author proposes that the first exemption date should be advanced to 1 day of age in order to make the chicks come into contact with the vaccine virus in advance and to have active immunity as soon as possible, increase the number of immunizations for infectious bronchitis, and make the flock more Protection: Egg-laying chickens should be immunized with inactivated vaccines before birth, and should be vaccinated with H120 drinking water or spray every 6-8 weeks after starting production to prevent egg drop caused by infectious bronchitis during egg production. Quality problems and tubal cysts.

In addition, the strengthening of feeding and management, doing a good job in biosafety, paying attention to disinfection, strict sanitation and disinfection measures, and a sound biological safety system are the key to preventing the disease. The chicken farm should be fully in and out. Normally, chicken sterilization work should be done to reduce the number of wild poisons in the environment. It is necessary to strengthen feeding and management in peacetime, pay attention to maintaining temperature, humidity, and reasonable ventilation in the house, and at the same time provide high-quality, full-priced feed, increase chicken population quality, and enhance disease resistance of chickens.

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