Newcastle disease, commonly known as Asian chicken plague, is an acute viral infectious disease, and chicken is the most sensitive among poultry. The main sources of infection are sick chickens and poisoned chickens. Viruses can enter the body through respiratory tract and digestive tract, conjunctiva, cloaca and damaged skin. This disease can occur in any season and any breed of chicken.

Main symptoms and pathological changes: Chickens suddenly come on and have a high mortality rate. Sick chickens are listless, eat less or stop eating, accumulate a lot of mucus in their mouths and noses, have difficulty breathing, often purr and discharge yellow-green or white loose stools. Laying hens lay pointed or soft-shelled eggs. Subacute or chronic chickens with a long course of disease often have nervous system symptoms, leg and wing paralysis or head and neck deviation, and dyskinesia. Autopsy found bleeding spots, bleeding spots or ulcers on glandular gastric papillae, swelling and bleeding of small intestinal mucosa, and bleeding of thymus, pectoralis minor, rectum, cecum and tonsil.

Prevention and control: ① Establish and improve the health and epidemic prevention system; ② Vaccinate well; (3) After the outbreak of the disease, the infected chickens should be blocked and isolated immediately, and thoroughly disinfected; (4) Dead chicken carcasses, feces, padding, etc. It should be burned, buried and disinfected.

2. Infectious bursal disease (IBD)

Infectious bursal disease (IBD) is a highly contagious disease that mainly affects chicks. The virus is transmitted through direct contact or toxic intermediates, and the main invasion routes are respiratory tract and digestive tract.

Main symptoms and pathological changes: Chickens are characterized by sudden onset and death, listlessness, loss of appetite, thin or white watery stool, drooping wings and stupidity. The seriously ill chicken died of severe fatigue. Some sick chickens recovered after a few days, but their development and weight gain were slow. Autopsy showed that the bursa of Fabricius was large, the color turned yellow or gray, and the mucous membrane was bleeding. In severe cases, it was "purple grapes". Sometimes the thigh and chest muscles bleed a little. The kidney is swollen and the ureter is blocked by urate.

Prevention and treatment: ① do a good job in vaccine immunization; (2) Injecting highly immune yolk liquid into chickens at the early stage of the disease; ③ Strengthen feeding management and health and epidemic prevention measures; ④ Control the secondary infection.

3. Marek's disease

Marek's disease is a viral infectious disease, which mainly infects chickens, and its susceptibility decreases with age. Sick chickens and infected chickens are the main sources of infection, which can be transmitted through respiratory tract, digestive tract and feathers of sick chickens.

Main symptoms and pathological changes: ① Nerve type: calf paralysis, split shape, drooping wings, cloudy iris, emaciation, swelling of sciatic nerve or pterygoid nerve, and disappearance of striations. ② Tumor type: Nodules formed on the skin or tumors in liver, kidney, heart and other internal organs, listlessness, loss of appetite, progressive emaciation and sudden death.

Prevention and control: ① Strictly implement the sanitation and disinfection system to disinfect breeding eggs, newborn chicks and brooding houses; ② Vaccinate one-day-old chicks seriously, and it is best for breeders to inject bivalent or trivalent vaccines.

4. Infectious bronchitis

Infectious bronchitis is only found in chickens and mostly occurs in chicks. Sick chickens and recovered infected chickens are the main sources of infection, which can be infected from respiratory tract and digestive tract.

Main symptoms and pathological changes: ① Respiratory type: breathing with the mouth open, sneezing, coughing, rales in trachea. General weakness, chills, listlessness, poor appetite, loose feathers and thin and white stools. The laying rate of laying hens dropped sharply, and the quality of eggs became worse. There is cheese-like exudate in trachea, bronchus and nasal cavity. ② Kidney type: The follicles of laying hens are congested, and the fallopian tubes shrink in the early stage of infection, forming a "fake hen" with swollen and pale kidneys.

Prevention and treatment: At present, there is no effective drug treatment. ① Strictly implement health and epidemic prevention measures such as quarantine, isolation and disinfection; (2) Strengthen environmental control, provide high-quality feed and enhance the resistance of chickens; ③ Vaccination: Attenuated vaccine is administered by nasal drops, eye drops or drinking water, and inactivated vaccine is administered by subcutaneous or intramuscular injection.

5. Infectious laryngotracheitis (ILT)

Infectious laryngotracheitis is the most typical symptom of adult chickens, which is infected through respiratory tract and conjunctiva.

Main symptoms and pathological changes: seriously ill chickens hold their heads up and stretch their necks to gasp, cough, sneeze, dyspnea, elevated body temperature, loss of appetite, listlessness, diarrhea and coughing up hemorrhagic mucus. Chickens with mild illness have symptoms such as conjunctivitis, tears, runny nose and swelling of suborbital sinus, and rarely die, but the laying rate decreases. The main pathological changes are bleeding and mucus at the upper end of larynx and trachea. In severe cases, the trachea is blocked, which affects breathing and suffocates.

Prevention and control: ① Adhere to strict isolation and disinfection system and pay attention to ventilation; ② Vaccinate as soon as possible and replace aerosol or drinking water with eye drops or nasal drops; ③ Pay attention to control diseases such as mildew and Escherichia coli.

6, chicken pox (pox)

Caused by poxvirus. Sick or infected chickens are the main source of infection.

Main symptoms and pathological changes: ① skin type: gray papules appear first, which merge with each other to form a dry, rough and brown scab; Mucosal type: a layer of cheese (cooked egg yolk)-like false membrane can be seen on the mucosa of larynx and trachea, which gradually expands and thickens, blocking the mouth and throat, resulting in dyspnea and dysphagia; ③ Mixed type: the skin and oral mucosa are diseased at the same time, with serious illness and high mortality.

Prevention and treatment: At present, there is no specific drug treatment, and the effective means is vaccination.

7. Egg drop syndrome (EDS-76)

Egg drop disease is a viral disease with no obvious symptoms in clinic, mainly because the egg production rate of chickens has dropped sharply. The disease can be transmitted to chickens by laying eggs.

The main symptoms and pathological changes: the chickens suddenly dropped eggs, the eggs were deformed, the color of brown-shelled eggs became lighter, and the quality of eggs decreased. Some chickens show fluffy feathers, anemia and diarrhea.

Prevention and control: ① Strengthen sanitation and disinfection; ② Vaccination; ③ Vitamins, calcium and protein can be supplemented appropriately.

8. Avian influenza

Avian influenza, once known as "chicken plague", is a viral disease that infects the respiratory tract, intestine or nervous system of many birds. According to different virus serotypes, there are low pathogenic types and high pathogenic types.

Main symptoms and pathological changes: sick chickens cough, sneeze, tracheal rales, tears, decreased egg production, diarrhea, eyelid edema and nervous system symptoms. Typical pathological changes are facial cyanosis and edema, ovarian hyperemia, bleeding and rupture. Abdominal fat, mucous membrane, serosa, leg and claw scales bleeding. There may be necrotic foci in internal organs.

Prevention and control: There is no reliable vaccine for the disease, and comprehensive prevention and control and strengthening quarantine are the main ways to avoid chicken infection.

9. Avian encephalomyelitis

Avian encephalomyelitis is a viral disease mainly affecting young chickens, which is characterized by dyskinesia and head and neck tremor. The egg production of laying hens may temporarily drop sharply.

Main symptoms and pathological changes: Spontaneous occurrence usually occurs in 1-2 weeks. At first, it was characterized by poor spirit and dull eyes, then head and neck tremor, dyskinesia, back and forth shaking, and finally out of control, unable to exercise, but still had an appetite until failure, and died of lack of diet. The lesion is not obvious to the naked eye. In severe cases, hepatomegaly and enteritis can be seen.

Prevention and control: ① Immunizing breeder chickens is the most effective method, and drinking water at 90- 100 days old is immune. ② Pay attention to feeding management to ensure the supply of various vitamins.

10, pullorum disease (SP)

The disease is an extremely common infectious disease, which is caused by Salmonella pullorum. Its excrement is an important transmission medium, and it can also be transmitted vertically through eggs.

Main symptoms and pathological changes: Chickens are characterized by not eating feed, being afraid of cold, curled up, drooping wings, depressed mood or lethargy, discharging white, sticky or yellowish and light green loose stools, and sometimes the anus is closed by induration feces, making it difficult to breathe. Adult chickens have no clinical symptoms, and a few seriously infected sick chickens show listlessness and yellow-green or egg white-like loose stools. The main pathological changes can be seen as swelling and fragility of liver and spleen, necrotic spots, dark red congestion of kidney or pale anemia, often accompanied by peritonitis. Laying hens can see ovary atrophy, eggs degenerate and sick chickens stop laying eggs.

Prevention and control: ① comprehensive prevention and control of pullorum disease in breeder farms, and quarantine and purification of breeders one by one; ② Drug treatment is available, and it is best to do drug sensitivity test first. Chloramphenicol and norfloxacin are generally better.

1 1, Escherichia coli

Escherichia coli is a ubiquitous conditional bacterium, and the infection route of the disease is mainly respiratory tract and digestive tract. Poor sanitation and disinfection of chicken houses and poor feeding management are the main causes of the disease.

The main symptoms and pathological changes: sick chickens are sleepy, their body temperature rises, their feathers stand on end, and they are often polluted by feces. Autopsy found that the spleen and liver were congested and swollen, and the liver and heart were inflamed, that is, perihepatitis and pericarditis, and mycoplasma was often mixed to cause pneumocystis and peritonitis. Often accompanied by respiratory diseases, clinical symptoms are not characteristic.

Prevention and control: ① Improve feeding management and do a good job in environmental sanitation and disinfection; ② It is best to do drug sensitivity test and choose sensitive drugs for prevention and treatment. Commonly used drugs include neomycin, chloramphenicol, streptomycin and furazolidone. (3) isolate Escherichia coli in the field and prepare inactivated vaccine for immune injection; ④ Microbial preparations can also be used from chicks.