How to prevent swine influenza in winter and spring?

Swine influenza (swine flu for short) is an acute, highly contagious respiratory infectious disease caused by a virus. The disease has a sudden onset and spreads rapidly, with a morbidity rate in pig herds as high as 100% and a low mortality rate. The disease is a zoonotic infectious disease. During an outbreak, the spread of the virus should be avoided as much as possible, and attention should be paid to protecting both keepers and veterinarians.

(1) Epidemiological characteristics: Swine influenza occurs mostly in late autumn, severe winter and early spring. Diseased pigs, latently infected pigs and chronic virus-carrying pigs are the sources of infection. The virus is present in the nasal fluid, tracheal and bronchial exudate, and pulmonary lymph nodes of affected pigs, and is mainly transmitted through the respiratory tract. Transmission is extremely fast, usually spreading throughout the entire herd within 2 to 3 days. If there is secondary or mixed infection with Actinobacillus pleuropneumoniae, Pasteurella, Streptococcus, Diplococcus and the like, the consequences are serious and can cause relatively large economic losses to the @#@227@#@ industry.

(2) Clinical symptoms: The incubation period ranges from a few hours to several days. The whole herd becomes ill at the same time within 2 to 3 days. Body temperature rises to 40 to 41°C, and in severe cases reaches as high as 42°C. Diseased pigs are depressed and have reduced or even completely lost appetite. They often lie on the ground and are unwilling to move; when forced to walk, they often limp. Diseased pigs have difficulty breathing, show abdominal breathing, and have paroxysmal coughing. Mucopurulent discharge flows from the mouth, eyes and nose, and the discharge often contains blood. The conjunctiva is congested, and growth of the diseased pigs stops. Pregnant sows often abort in the later stages of pregnancy.

(3) Pathological changes: The respiratory mucosa is congested and swollen, with a large amount of foamy mucus on the surface, sometimes containing blood. The lymph nodes of the neck, lungs and mediastinum are edematous and congested, with everted cut surfaces and a juicy appearance. The affected lung tissue is purplish red and shrunken, with a clear boundary from the surrounding healthy tissue. The thoracic cavity contains mucous and fibrinous exudate. The gastric mucosa is severely congested, and the large intestine shows patchy congestion. The spleen is slightly enlarged.

(4) Diagnostic basis: A preliminary diagnosis can be made based on epidemiological characteristics, clinical symptoms and pathological changes. The disease usually occurs in early spring, late autumn and severe winter, and when there is a sudden change in climate. Pigs of all ages, breeds and sexes are susceptible, with high morbidity and low mortality. Diseased pigs show fever, coughing and runny nose. The lesions are mainly concentrated in the bronchi and lungs. Differential diagnosis should mainly distinguish it from swine pasteurellosis, acute swine enzootic pneumonia, tuberculosis, porcine contagious pleuropneumonia, toxoplasmosis and lungworm disease.

(5) Prevention and control measures: The treatment principles for this disease are symptomatic treatment and control of secondary infection. Isolate diseased pigs promptly, improve the rearing environment, strengthen disinfection, ensure high-quality feed and sufficient drinking water, and add multivitamins and minerals. (1) Yinhuang Reduqing injection (Jiangxi Gannan Huayi Pharmaceutical Factory) at 0.1 to 0.15 mL per kg body weight, mixed with kanamycin at 230,000 to 400,000 international units per kg body weight, then given as a single intramuscular injection, twice a day for 3 consecutive days. (2) Amantadine hydrochloride tablets, taken orally, twice a day for 3 consecutive days. At present, there is no commercial vaccine for this disease in China. In normal times, feeding management should be strengthened, and sanitation and disinfection of pig housing should be done well. Once the disease occurs, it is very difficult to stop its spread within the herd. It can only be managed by improving feeding management, strengthening disinfection work, and administering antibiotics to control secondary infection, so as to reduce the number of affected pigs and lessen economic losses.