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Special topics on swine diseases: Swine Influenza
2024-12-12
Swine influenza is an acute, infectious respiratory disease in pigs caused by the swine influenza virus (SIV). It is characterized by sudden onset, coughing, difficulty breathing, fever, and rapid progression. Swine influenza is a respiratory disease in pigs caused by the virus. It is caused by an influenza A virus (H1N1 subtype) and usually occurs in outbreaks among pigs, with high transmissibility but typically not causing death. The disease is more common in the autumn and winter months, although it can spread year-round.
Epidemiological Characteristics: Pigs of all ages, sexes, and breeds are susceptible to this virus. The disease has a distinct seasonal pattern, with outbreaks occurring frequently in the late autumn, early spring, and cold winter months. The disease spreads rapidly and can occur as either localized outbreaks or widespread epidemics. It has a high morbidity rate but a low mortality rate (4%–10%). Infected pigs and carriers are the sources of swine influenza transmission, and pigs may remain carriers for 6 to 8 weeks after recovery.
Symptoms: The disease has a high incidence, with an incubation period of 2 to 7 days and a duration of about 1 week. In the early stages of infection, affected pigs suddenly develop fever, lethargy, reduced or complete loss of appetite, often lie down together, are reluctant to move, experience difficulty breathing, and exhibit severe coughing. Nasal and ocular discharge of mucus is commonly observed. If treatment is delayed during the course of the disease, secondary complications such as bronchitis, pneumonia, and pleuritis can occur, increasing mortality.
Infected pigs may experience a body temperature increase up to 40°C–41.5°C, depression, reduced or absent appetite, muscle pain, reluctance to stand, mucous discharge from the eyes and nose, conjunctival congestion, and in some cases, difficulty breathing, panting, coughing, abdominal breathing, and a dog-sitting posture. Wheezing sounds can be heard at night, and joint pain, particularly in pigs with better body condition, may occur.
Pathological Changes: The pathological changes in swine influenza primarily affect the respiratory organs. The mucous membranes of the nose, pharynx, larynx, trachea, and bronchi become congested and swollen, with a thick liquid covering the surface. Small bronchi and bronchioles fill with frothy exudate. The thoracic and pericardial cavities accumulate large amounts of serous fluid mixed with fibrin. Pulmonary lesions typically occur in the apical, cardiac, interlobar, and diaphragmatic lobes, with clear boundaries from surrounding tissues, showing colors from red to purple, with collapsed, solid, leathery texture. The spleen is enlarged, and the lymph nodes of the neck, mediastinum, and bronchi are swollen and moist.
Prevention and Control Measures:
1.Strengthen feeding management, meet the nutritional needs of the pig herd, regularly clean and disinfect the environment, and isolate and treat infected pigs promptly.
2.Isolate affected pigs in a timely manner. Disinfect pens and feeding equipment with a 1% Roxycide solution. Dispose of leftover feed and water by deep burial or other non-polluting methods. Add 0.05% moroxydine hydrochloride to the pigs' feed for one week.