Prevention and treatment of Newcastle disease in chickens

Chicken Newcastle disease, also known as Asian chicken plague, is a highly contagious, acute and severe infectious disease caused by chicken Newcastle disease virus. Often show septicemia, the main features are dyspnea, dysentery, neurological disorders, mucous membrane and serosa bleeding.

I. popular characteristics

All kinds of chickens and chickens of all ages can be infected, young and middle chickens are more likely to be infected, and old chickens more than two years old are less susceptible. The main sources of infection of the disease are diseased chickens and infected chickens. Their secretions, feces, contaminated feed and drinking water, non-susceptible wild birds, external parasites, humans and livestock can spread the disease. The main route of transmission is the digestive tract and respiratory tract, and it can also invade the body through injured skin and mucous membrane. It can happen all the year round. In non-immune areas or low-immune chicken flocks, once a rapid strain invades, it can spread rapidly, showing a devastating epidemic, and the morbidity and mortality can reach more than 90%. At present, when chickens in large and medium-sized farms have certain immunity, Newcastle disease mainly occurs in an atypical form, which should be paid attention to.

Symptoms and pathological changes

The incubation period of Newcastle disease in chickens is generally 3 to 5 days. According to the clinical manifestation and course of disease, Newcastle disease can be divided into the most acute, acute and chronic types.

1 the most acute type: diseased chickens often die suddenly without any symptoms. It is more common in the early stage of the epidemic and chicks.

(2) Acute type: the body temperature at the beginning of the disease was as high as 43 ℃ ~ 44 ℃, suddenly dieting or not eating, and the chicken crown and droop were crimson or purplish black. Mental fatigue, standing apart from the group, drooping head and neck or drooping wings, sleepy. Diarrhea, faeces are yellowish green or yellowish white, sometimes mixed with blood. Diseased chicken mouth, nose, pharynx, throat accumulate a lot of mucus, shake the head to swallow frequently, open mouth to breathe, and make a gurgling sound or sharp cry and cough. The crop is filled with liquid and gas, and a large amount of liquid flows out of the mouth when lifting backwards. Some chickens also have neurological symptoms such as wing and leg paralysis. In the later stage of the disease, the body temperature drops and soon dies. The course of disease is usually 2-5 days.

3 chronic type: the initial symptoms of the disease are roughly the same as acute, and soon appear neurological symptoms, leg and wing paralysis, claudication or lying on the ground. Head and neck back or to one side twist, often rotate, movement imbalance, repeated attacks, and finally paralyzed or semi-paralyzed. It usually takes 10 to 20 days to die. This type mostly occurs in adult chickens in the later stage of the epidemic, chickens whose immunization quality is not high or whose immunization period is close to the end.

III. Treatment

At present, there is no effective drug for the diagnosis and treatment of Newcastle disease.

IV. Prevention

The key to the prevention of Newcastle disease is timely immunization and the implementation of comprehensive prevention and control measures.

1 Comprehensive prevention and control measures: strengthen feeding and management to improve disease resistance and immune response of chickens. Strictly isolate and disinfect and cut off the route of transmission. Large and medium-sized chicken farms should implement the "all in and all out" system, refuse visits, strengthen quarantine, prevent animals from entering susceptible chickens, and the entry and exit of staff and vehicles must be strictly disinfected.

2 Preventive vaccination: at present, the most commonly used vaccines in China are Newcastle disease Ⅰ, Ⅱ, L (Lasota) live vaccine and oil emulsion inactivated vaccine. Vaccine use should be based on the actual situation to develop their own immunization procedures and immunization routes. Aerosol and drinking water are often used in large chicken farms, while nasal dripping and injection can be used in small chicken farms and farm chickens.

Ⅰ vaccine is a moderately virulent live vaccine with fast immunity (3-4 days) and a long immune period of more than one year, but it has a certain pathogenicity to chicks. It is often used in chickens immunized with weak virulence vaccine or chickens over 2 months old, which are inoculated by intramuscular injection or pricking inoculation. Ⅱ strain and L line vaccine belong to weak virulence vaccine, which can be used in both big and small chickens. Nasal drops, eye drops, drinking water and aerosol are often used to inoculate. The oil emulsion inactivated vaccine is safe for chickens, can produce strong and lasting immunity, and does not spread the pathogen through the vaccine, but it takes 10 to 20 days to develop immunity after injection.

5. Treatment of Newcastle disease in chicken farms

Once the disease occurs in chickens, the suspected diseased chickens should be burned or buried deeply, and the contaminated feathers, bedding grass and faeces should also be buried or burned. Close the chicken farm, prohibit transfer or sale, immediately and thoroughly disinfect the environment, and give chickens double the dose of Ⅰ vaccine emergency vaccination; if there are chicks in the farm, they should be strictly isolated to prevent Ⅰ vaccine from infecting chickens. After two weeks of treatment of the last case, and through strict disinfection, the blockade can be lifted and the chicken can be re-entered.