Newcastle disease is also known as Asian chicken plague and pseudo-chicken plague. An acute, high-exposure infectious disease in chickens and other poultry caused by Newcastle disease virus. The main features are dyspnea, diarrhea, neurological disorders, bleeding from the mucous membrane and serous membranes, hemorrhagic fibrous necrotizing enteritis, necrosis of lymphoid tissues such as the spleen, thymus, supraluminal sac and lymphatic follicles of the intestinal wall.
The virus exists in the blood, feces, sac fluid, spleen, liver, kidneys, lungs, trachea, bone marrow and brain of sick chickens, with the brain, spleen and lungs containing the highest toxicity and the bone marrow containing the longest toxicity.
The virus can survive for 7 weeks in chicken coops, 5 1/2 months in chicken manure at 50"C, 98 days in chicken carcasses, and 134 days in bone marrow. Newcastle disease virus is not strongly resistant to general disinfectants, and 2% sodium hydroxide, 1% lysol, 3% carbolic acid, and 1% to 2% formaldehyde solution can kill it in a few minutes.
There are also differences in susceptibility among chickens of all ages, with young and middle chicks being the most susceptible. Newcastle disease can occur all year round, but it occurs more often in winter and spring, and the incidence decreases in summer, and occurs more often before and after traditional festivals.
The main source of infection of the disease is sick chickens infected with Newcastle disease, which are in contact with healthy chickens and are infected through the respiratory and digestive tracts. The secretions of the sick chicken contain a large amount of virus, which contaminates the feed, drinking water, ground, utensils, and is infected through the digestive tract. Dust and droplets with the virus enter the respiratory tract and are infected through the respiratory tract.
[Symptoms]
(1) The most acute type of sudden onset, often without characteristic symptoms and rapid death.
(2) At the beginning of acute disease, the body temperature rises as high as 43 ~ 44C, the appetite is reduced, the spirit is satisfied, the reluctance to move, the head is hanging down and the neck is shrunken, the eyes are half closed, and it seems to be sleepy. With the development of the course of the disease, the sick chicken coughs, has difficulty breathing, has mucus nasal leakage, often stretches its head, opens its mouth to breathe, and makes a "clucking" wheezing sound, and the crown and flesh of the chicken gradually become dark red or dark purple. A large amount of mucus often flows out from the corners of the mouth, and in order to discharge this mucus, the sick chicken often shakes or swallows. The stool is thin, yellowish-green or yellowish-white, and the stool is white-like in the later stages. Some sick chickens also have neurological symptoms, such as paralysis of the wings and legs, and finally their body temperature drops and they die soon after.
(3) Chronic type
Sick chicken wing legs are paralyzed, paralyzed or unstable in standing, the head and neck are tilted to one side, or twisted backwards, often rotating, motor disorders, recurrent attacks, aggravated by stimulation. Except for some that can be recovered, it usually dies after 10 to 20 days. This type occurs mostly in adult chickens in the late epidemic period and has a low fatality rate.
[Pathological changes]
(1) The most acute type is due to the sudden onset of the disease, most of which have no lesions visible to the naked eye, and individual dead chickens can see bleeding spots on the medial sternum and epicardial membrane.
(2) The comparative characteristics of acute lesions are that there is a large amount of mucus and dirt in the mouth, the sac is filled with a large amount of sour and smelly liquid and gas, and there are bleeding classes, bleeding bands or ulcers at the junction of the esophagus and the glandular stomach. Swelling of the glandular stomach, bleeding from the nipples, in severe cases bleeding from the glandular gastric wall between the nipples, and subkeratoemorrhagic bleeding in the muscles and stomachs. The rectal mucosa is often densely packed with needle-tip-sized bleeding spots. There is a large amount of mucus in the throat and trachea, and there is severe bleeding.
[Prevention]
Strengthen feeding management to prevent pathogens from invading the flock. Immunization is an effective means of preventing Newcastle disease, and the conventional vaccines currently used mainly include various weak vaccines and inactivated vaccines with different virulences. Chicken farms with conditions should determine the immunization program based on the results of antibody level monitoring, and chicken farms without monitoring conditions can refer to the following immunization procedures.
Broiler
(1) 7-8 days old Newcastle disease IV vaccine point eye or nose drops, subcutaneous injection of Newcastle disease inactivated oil emulsion vaccine.
(2) Drinking water from 21 to 22 days old Newcastle disease IV vaccine.
(3) Drink water with Newcastle disease IV vaccine at 31 to 32 days old.
[Treatment]
After the onset of the disease in the flock, there is no specific treatment, and emergency immunization measures should be taken. The daily age of the chicken can be seen, and the eye or water is doubled with the IV vaccine.
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