(2) Digestive system: diarrhea, discharging green feces.
(3) Nervous system: tremor and neck distortion.
(4) Oviposition: the amount of oviposition decreases, resulting in abnormal eggs, and the eggshell turns white and thin; The number of dead embryos increases in the early stage of incubation.
Autopsy symptoms (1) Respiratory system: tracheal congestion turns red (tracheitis), alveolar infection (pneumonia), complicated with chronic respiratory diseases.
(2) Digestive system: there are bleeding spots in glandular stomach papilla, intestinal infection bleeding and cecal tonsil bleeding.
(3) Reproductive system: follicle atrophy and yolk rupture.
Diagnostic methods When the feed intake of chickens suddenly drops, respiratory symptoms and loose green feces appear, and the egg production of adult chickens drops obviously, the possibility of Newcastle disease should be considered first. Through careful observation of chickens, respiratory tract, digestive tract and nerve symptoms were found, and combined with as many clinical and pathological autopsy as possible, if pathological changes characterized by bleeding, necrosis and ulcer of digestive tract mucosa were seen, Newcastle disease could be preliminarily diagnosed. Viruses should be isolated and identified for diagnosis. It can also be judged by serological diagnosis.
① virus culture and identification: after the sample was treated, SpF chicken embryos aged 9 ~ 10 were inoculated, incubated at 37℃ for 4 ~ 7 days, and allantoic fluid was collected for HA test to determine the titer, and the existence of nd virus was determined by specific antiserum (chicken antiserum) or I test.
② Virulence determination: the pathogenicity index of 1 day-old chicks inoculated in the brain, the pathogenicity index of 6-week-old chicks inoculated intravenously and the average death time of chick embryos were determined.
Serological tests: virus hemagglutination test (HA), virus hemagglutination inhibition test (HI), enzyme-linked immunosorbent assay (ELISA, used for on-site diagnosis, epidemiological investigation and screening of entry-exit chicken quarantine).
Sample collection: used for virus separation. Brain, lung, spleen, liver, heart, kidney, intestine (including contents) or mouth and nose swabs can be collected from dead or dying birds. Except for intestinal contents, the above samples can be collected separately or mixed. Or collect tracheal and cloacal swabs from live birds. Young birds or rare birds are prone to damage when collecting swabs, so they can collect fresh feces instead. The above samples are immediately sent to the laboratory for processing or stored at 4℃ (no more than 4 days) or 30℃ for testing.
Samples used for serological detection generally collect serum.
Preventive measures 1, do a good job of sanitation and disinfection, strengthen feeding management, and prevent pathogen invasion.
2. Immunization is the key to prevent Newcastle disease. Commonly used vaccines are attenuated live vaccine and inactivated oil emulsion vaccine. The immunization program should be arranged reasonably according to the maternal antibody level and local epidemic situation.
2. 1 Prevention in advance
Find out the nature, object and method of vaccine.
At present, there are mainly four kinds of Newcastle disease vaccines used in China, namely I strain (or Mjukteswar), II strain (or HBI strain), III strain (or F strain) and IV strain (or Lasota strain). Strain I vaccine is a live vaccine with moderate toxicity. Used for chickens immunized with attenuated vaccine twice or chickens over 2 months old.
The export of broilers is strictly prohibited. Inoculation is usually by intramuscular injection or seed puncture. Chickens will cause serious vaccination reaction after using it, and even get sick and detoxify, so it's okay. The advantages of this vaccine are that it produces immunity quickly (3-4 days) and the immune period is long (more than one year). It is usually used for emergency vaccination in affected areas.
Strains Ⅱ, Ⅲ and Ⅳ are attenuated live vaccines, which can be used by chickens of all ages. Most of them are suitable for newborn chicks over 0 who are inoculated with nasal drops, eye drops, drinking water and aerosol. After inoculation, they develop immunity within 7-9 days. The immune period of newborn chicks is 3-4 months, and the immune period of adult chicks over 5 months is one year. For a large group of chicks, vaccine ⅲ or ⅳ can be used as drinking water immunization or aerosol immunization, but it is best to use it after 2 months to reduce the induction of respiratory diseases.
Clonal strain: the clonal strain of Lasota has the same virulence as B 1, the same immunogenicity as Lasota, and the effect is good.
Oil emulsion vaccine: safe, long immune period and good shelf life.
Note: Attenuated vaccine and inactivated vaccine should be used at the same time.
Immune monitoring: Unsafe chicken farms under 6 should be vaccinated.
Immunosuppression: refers to the inhibition of antibody production after vaccination, and the protection ability is seriously affected.
2.2 Prevention and control measures of Newcastle disease:
2.2 1 vaccination
At the age of 7 days after hatching, chicks were immunized with attenuated vaccine for the first time, that is, strains Ⅱ, Ⅲ and Ⅳ were diluted with distilled water or cold boiled water 10~20 times, then 2-3 drops were dripped into nostrils with dropper, and 0.3ml oil seedlings were injected at the same time, and immunity was generated after 7 days. The immune period of newborn chicks is 3~4 months (this chick can also be bigger than the big chicken); At the age of 24~26 days, the attenuated vaccine was used for the second immunization, and 0.5ml of oil vaccine was injected at the same time. Chickens over 2 months old were immunized with I vaccine for the third time, diluted with cold water or distilled water 100 times, dipped in sterile pen tip and inoculated under the skin of the inner wing. After 3 days, immunity was produced, and the immune period was 2 years. Subcutaneous injection is also feasible, even when the rice grain is big.
1 10~ 120-day-old intramuscular injection of Newcastle disease oil vaccine.
2.22 Drinking water immunization should pay attention to:
(1) Stop drinking water about 6 hours before immunization.
(2) The water for diluting the vaccine should be clean.
(3) The drinking fountains should be sufficient and clean to ensure that everyone can drink enough water, and avoid exposure to sunlight or close to heat sources.
(4) The diluted vaccine should be used up on the same day and cannot be used again the next day.
Treatment plan Once the chickens get sick, emergency measures should be taken to prevent the spread of the epidemic. Its measures include emergency disinfection and emergency vaccination of all chickens. The method is as follows:
Once typical chicken plague occurs in chickens over 2 months old, I-strain vaccine is injected into muscle or inoculated. Rescuing sick chickens with a large dose of strain I vaccine, that is, diluting 100 times and injecting 1 ml into the chest muscle of each chicken, can stop the death after 3 days. After injection, some sick chickens will be eliminated and dead chickens will be burned. And should be tightly sealed, often disinfected, and die after half a month of illness, and then carry out a major disinfection, and then lift the blockade. In the case of atypical Newcastle disease, non-laying hens can be injected with strain I vaccine twice, and laying hens can be injected with attenuated vaccine twice.
Emergency injection of Newcastle disease high immune serum or high immune yolk antibody at the initial stage of onset under 2 months old; It can also reduce deaths and quickly control the epidemic. Pay attention to the injection amount of 2~4ml, and inject again the next day. The effect is very good. After the epidemic situation was controlled, the whole group was immunized with ⅳ vaccine or clonal vaccine again. In case of atypical Newcastle disease, you can double the attenuated vaccine.
Antibacterial drugs, such as penicillin, streptomycin, ciprofloxacin, azithromycin, tylosin, etc. It can be used to prevent secondary respiratory and digestive tract infections. Chinese medicine (Qingwen Baidu Powder), vitamin C, quick supplement and other vitamins are added to feed or drinking water to promote the recovery of the body.
Pathogenic factors There are many factors leading to the occurrence of Newcastle disease, mainly including the following aspects:
(1) Chickens are in poor health.
Stress during transportation, drastic changes in season and temperature, rainy season, excessive density of chickens and infection with other diseases will all affect the health of chickens.
(2) the immune system
Cellular immunity is mainly influenced by the health status of the body, while humoral immunity is influenced by maternal antibodies and immunity. If HI test shows that the antibody titer of ND is lower than 64 or EL
The antibody titer detected by ISA method is less than 2000, which indicates that the chickens are in a susceptible state.
(3) integrity of respiratory tract and digestive tract mucosa
Most pathogens can't invade the intact primary defense system (skin and mucosa), or will be excreted with mucosal secretions. Nutritional deficiency (biotin deficiency) or
Some infectious pathogens destroy the body's primary defense system (skin and mucous membrane), which will make some pathogens invade the body. Malnutrition, if vitamins a and b
And C can meet the needs of the body, then the mucosa will be protected to a certain extent. Because these vitamins help to maintain epithelial cells of mucosa and skin.
(4) Indoor feeding density
Excessive feeding density will lead to the spread of diseases.
(5) Poor feeding management
For example, the padding is wet, the ammonia concentration is too high, and the quality of feed and drinking water is poor.
Immune programmed broiler
15-day-old Lasota attenuated vaccine was eye-dropped, sprayed or drank twice as much water.
Laying hens and breeders
7-day-old Lasota was given nasal drops and eye drops, and 0.3ml of nd inactivated vaccine was injected into muscle. 28-day-old Lasota was immunized by spraying or drinking water twice; 9-week-old Lasota spray immunization; If necessary, consider injecting intensified I series vaccine; Inactivated ND+EDS+IB vaccine was injected into muscle 2 ~ 3 weeks before operation, and Lasota was sprayed or sprayed. Spraying live seedlings with ND+IB every 6 ~ 10 week after opening; At the age of 44 weeks, the re-immunization effect with ND inactivated vaccine was better.