I. Newcastle disease in chickens
Caused by Newcastle disease virus, it can occur throughout the year and is acute in onset, severe, fast-spreading, and associated with a high mortality rate. Affected chickens generally show difficulty breathing, diarrhea, green feces, depression and neurological symptoms, swelling of the head and face, and cessation of egg production. The mortality rate in susceptible flocks can reach 90%–100%. Prevention: Vaccination is the primary method. Administer a Newcastle disease–infectious bronchitis bivalent vaccine by nasal drops at 3 days of age; administer the monoclonal vaccine via drinking water at 10 days of age; repeat at 30 days of age; and administer the I strain vaccine by injection at 60 days of age. Alongside immunization, strengthen disinfection efforts. If sick chickens are found, isolate them promptly and dispose of them harmlessly to ensure treatment effectiveness.
II. Infectious bursal disease
Caused by infectious bursal disease virus, this disease can seriously harm the poultry industry. Clinical signs include affected chickens passing loose white or light-green droppings, lethargy, a drooping head, closed eyelids, and ruffled feathers, followed by extreme exhaustion and death. Preventive measures: administer live attenuated infectious bursal disease vaccine once via drinking water at 1–7 days of age, then administer a second immunization at 24 days of age. For prevention, strengthen disinfection of the chicken house, reduce stress, and provide ample drinking water, to which 5% sugar and 0．1% salt may be added to improve the chickens’ disease resistance.
Three, infectious bronchitis in chickens
An acute, highly contagious respiratory disease caused by infectious bronchitis virus; chickens are the only natural host. Affected chickens show tracheal rales, coughing, and sneezing. The disease can cause the death of young chickens and a marked reduction in egg production in adult chickens. Chickens of all ages can be infected, but chicks under 6 weeks of age are most susceptible. The disease spreads rapidly, and nearly all susceptible chickens with a history of contact become ill at almost the same time. Prevention and control measures: administer vaccine to chicks aged 3–5 days by nasal drops or in drinking water at double the dose; give a booster vaccination at double the dose when they are 1–2 months old. There is no specific treatment for this disease. Early use of antibiotics can prevent secondary infections. If necessary, symptomatic treatment may be given, such as providing the flock with drinking water containing 0．5%–1% baking soda for 3 consecutive days. Starting on day 4, gradually reduce the amount of medication. Medication is generally given for 7 days and may reduce the mortality rate.
Four. Pullorum disease
Caused by Salmonella, it mainly affects chicks up to 2–3 weeks of age. It is characterized by acute septicemia and the passage of white, paste-like feces, with high morbidity and mortality. Sick chicks appear lethargic and have a poor appetite; their wings droop and feathers are ruffled. They tend to squat and pass yellowish-white or green feces. Control measures: The key to preventing pullorum disease is to promptly identify and cull carrier birds from the flock. Chicks should be sourced from breeding farms free of pullorum disease. In the event of an outbreak, norfloxacin, ciprofloxacin, or enrofloxacin can be administered in drinking water for treatment.
V. Fowl cholera
An acute infectious disease in poultry caused by certain serotypes of Pasteurella multocida. In addition to chickens, waterfowl such as ducks and geese can also be infected. Its clinical features are severe diarrhea and septicemia in birds with the acute form, and symptoms such as wattle edema and arthritis in those with the chronic form. Fowl cholera is widespread and poses a major threat to the poultry industry. Prevention and control measures: The key to preventing this disease is proper routine feeding and management, and diligent implementation of the poultry farm’s hygiene and disease-prevention protocols. Chicks can be given an intramuscular injection of inactivated fowl cholera vaccine at 30 days of age for prevention. Mild cases can be treated with sulfonamides, antibiotics, olaquindox, or other medications.
Six. Escherichia coli disease
Chicken colibacillosis is the general term for a range of diseases in chickens caused by certain serotypes of Escherichia coli. This is an opportunistic disease that often occurs when environmental conditions change. Clinical signs and pathological changes vary widely, and the disease is characterized by inflammation of various organs, including pericarditis and perihepatitis. Preventive measures: Strengthen flock management, reduce stocking density, regularly disinfect poultry houses and exercise areas, and ensure that feed and drinking water are clean. When chicks begin eating, mixing medication into their feed or drinking water for them to consume can provide some preventive effect. Commonly used medications include neomycin, gentamicin, and nitrofuran drugs.