How to prevent and treat Newcastle disease in chickens? These methods you need to master

Newcastle disease in chickens, also called Asian fowl pest, commonly known as fowl plague, is a highly contagious, acute, and virulent infectious disease of chickens caused by Newcastle disease virus. It often presents as septicemia, with the main features being difficulty breathing, diarrhea, nervous system disorders, and hemorrhage of mucous membranes and serous membranes.

I. Epidemiological characteristics

Chickens of all breeds and ages can be infected, with young chickens and growing chickens being more susceptible, and older chickens over two years of age having reduced susceptibility. The main sources of infection for this disease are sick chickens and virus-carrying chickens; their secretions, feces, as well as contaminated feed, drinking water, non-susceptible wild birds, external parasites, humans and livestock can all transmit the pathogen. The main routes of transmission are the digestive tract and respiratory tract, and it can also invade the body through damaged skin and mucous membranes. It can occur in all four seasons. In non-immune areas or in flocks with low immunity, once a velogenic strain invades, it can spread rapidly, causing a devastating epidemic, with morbidity and mortality reaching over 90%. At present, in large and medium-sized @#@230@#@ farms, where flocks have a certain level of immunity, Newcastle disease mainly appears in an atypical form, which should be given attention.

II. Symptoms and lesions

The incubation period of Newcastle disease in chickens is generally 3 to 5 days. According to clinical manifestations and disease course, it can be divided into three types: peracute, acute, and chronic.

1. Peracute type: sick chickens often die suddenly without any symptoms. It is mostly seen in the early stage of an epidemic and in chicks.

2. Acute type: at the beginning of the disease, body temperature rises as high as 43°C to 44°C, with sudden reduced feeding or no feeding, and the comb and wattles appear dark red or purple-black. The chickens are listless, stand alone away from the flock, droop their heads and hunch their necks or droop their wings, and are lethargic and drowsy. There is diarrhea, with feces being yellow-green or yellowish-white, sometimes mixed with blood. A large amount of mucus accumulates in the mouth, nose, pharynx, and larynx of sick chickens; they shake their heads and frequently swallow, breathe with their mouths open, and emit a clucking wheezing sound or sharp cries and coughing. The crop is filled with fluid and gas, and when held upside down, a large amount of fluid flows out of the mouth. Some chickens also show nervous symptoms such as paralysis of the wings and legs. In the late stage of the disease, body temperature drops, and death follows shortly. The course of the disease is mostly 2 to 5 days.

3. Chronic type: the initial symptoms are roughly the same as the acute type, and soon nervous symptoms appear, with paralysis of the legs and wings, lameness, or lying on the ground. The head and neck twist backward or to one side, and the chickens often lie on the ground and spin, with loss of coordination, recurring episodes, and eventually paralysis or partial paralysis. Death generally occurs after 10 to 20 days. This type mostly occurs in adult chickens in the late stage of an epidemic, and in flocks with low-quality vaccination or whose immune validity period is nearing its end.

III. Treatment

At present, there are no effective therapeutic drugs for the diagnosis and treatment of Newcastle disease in chickens.

IV. Prevention

The key to preventing Newcastle disease in chickens is timely vaccination and the implementation of comprehensive prevention and control measures.

1. Comprehensive prevention and control measures: strengthen feeding management, improve the disease resistance of chickens and their immune response. Strictly isolate and disinfect, and cut off transmission routes. Large and medium-sized chicken farms should implement an "all-in, all-out" system, refuse visitors, strengthen quarantine, prevent animals from entering susceptible flocks, and staff and vehicles must undergo strict disinfection when entering and leaving.

2. Vaccination: at present, the most commonly used vaccines in our country are Newcastle disease strain I, strain II, and L (Lasota) live vaccines and oil-emulsion inactivated vaccines. The use of vaccines should be based on actual conditions to formulate one's own immunization program and immunization routes. Large chicken farms mostly use aerosol and drinking water immunization; small chicken farms and rural household chicken raisers can use methods such as nasal drops and injection.

Strain I vaccine is a live vaccine of moderate virulence, producing immunity quickly (3 to 4 days), with a long immune period lasting up to more than 1 year, but it has a certain pathogenicity to chicks, so it is often used for chickens that have been immunized with attenuated vaccines or chickens over 2 months of age, mostly by intramuscular injection or wing-web stab vaccination. Strain II and L strain vaccines are attenuated vaccines, suitable for both large and small chickens, and are mostly administered by nasal drops, eye drops, drinking water, and aerosol. Oil-emulsion inactivated vaccines are safe for chickens, can produce strong and lasting immunity, and will not spread the pathogen through the vaccine, but immunity is only produced 10 to 20 days after injection.

V. Handling of Newcastle disease outbreaks on chicken farms

Once this disease occurs in a flock, first detect suspicious sick chickens and burn or deeply bury them; contaminated feathers, litter, and feces should also be deeply buried or burned. Lock down the chicken farm, prohibit moving or selling, immediately thoroughly disinfect the environment, and carry out emergency vaccination of the flock with double the dose of strain I vaccine; if there are chicks on the chicken farm, they should be strictly isolated to avoid infection of chicks by strain I vaccine. The lockdown can only be lifted and new chickens introduced after two weeks from the handling of the last case and after strict disinfection.