How to Diagnose and Treat Swine Influenza in Winter and Spring

Swine influenza is an acute, highly contagious respiratory infectious disease. The disease strikes suddenly, spreads rapidly and has a high incidence rate. In winter and spring, sudden climate changes, extensive feeding management, malnutrition of pigs and reduced resistance can easily lead to outbreaks and epidemics of the disease.

1 Epidemic characteristics

Seasonality is obvious, and it mostly occurs in autumn and winter when temperatures change abruptly, and in spring. Pigs of all ages can be infected. The virus is present in the nasal fluid, tracheal and bronchial exudate, lungs and pulmonary lymph nodes of affected pigs. It is mainly transmitted through air and droplets, infecting via the respiratory tract, and the disease spreads extremely quickly. The incidence rate is generally high, while the mortality rate is relatively low. If secondary infection with Pasteurella, Streptococcus pneumoniae, etc. occurs, the condition worsens and causes relatively large economic losses.

2 Clinical symptoms

The incubation period of the disease can be as long as 1 week, and body temperature can reach around 40°C. Affected pigs show a sharp decrease in appetite or complete loss of appetite, are highly depressed, have muscle and joint pain and stiffness, are unwilling to stand, have difficulty walking, breathe rapidly and shallowly, prefer abdominal breathing or a sitting dog posture, with paroxysmal coughing and clear watery nasal discharge, initially serous and later turning mucous and purulent; generally they can fully recover in 2-6 d, and the mortality rate is not high.

3 Key points for diagnosis

3.1 Pathological changes. Based on the epidemic characteristics of sudden onset, rapid spread through the whole herd with a benign course, persistent high fever and respiratory symptoms as the main clinical signs, a definitive diagnosis can be made in combination with necropsy changes. Pathological necropsy mainly shows changes in the respiratory organs: congestion of the nasal, laryngeal, tracheal and bronchial mucosa with a large amount of mucus on the surface; sometimes the bronchi are blocked by viscous exudate; the gastrointestinal tract mainly shows congestion, with no obvious hemorrhage.

3.2 Differential diagnosis. Affected pigs show fever, coughing and nasal discharge, and the lesions are mainly concentrated in the bronchi and lungs. Endemic bronchopneumonia of piglets only infects piglets, its infectivity is much lower than that of swine influenza, and its clinical course is not very acute, mostly subacute or chronic, with symptoms such as diarrhea and skin eczema; in swine influenza there is no congestive or hemorrhagic erythema or red spots on the skin, and there is also no vomiting or significant gastrointestinal dysfunction; swine plague is mainly characterized by systemic hemorrhagic septicemic lesions, with petechiae and ecchymoses on the skin, serosa and mucosa, and enlarged and hemorrhagic lymph nodes, whereas swine influenza shows catarrhal symptoms of all respiratory mucosa, with such changes in the nasal cavity, trachea and bronchi, and swollen lymph nodes.

4 Preventive measures

4.1 Strengthen feeding management, do a good job in the environmental hygiene and disinfection of pig houses, especially supplement vitamins; when necessary, sulfonamide drugs can be given orally for prevention, and multivitamins and minerals should be added.

4.2 Keep pig houses dry and clean, pay attention to ventilation in summer, and pay attention to cold protection and warmth in winter.

4.3 Isolate affected pigs as early as possible and carry out strict and thorough disinfection to prevent further spread of the disease.

5 Treatment plan

5.1 The drug of first choice is amantadine hydrochloride. It can prevent the virus from entering cells, causing the influenza virus to die due to lack of nutrition.

5.2 When pigs show influenza-like symptoms, intramuscular injection of swine leukocyte interferon supplemented with antibiotics and vitamins B and E, etc. can effectively control secondary infection. For secondary infection, symptomatic treatment can be combined with penicillin potassium powder for injection (4 million), Bingdu Mie injection, Zhongmei Jindian injection, etc.

5.3 Mix antiviral No. I powder (400 kg feed/bag) + doxycycline 300 mg/kg into the feed, mix continuously for 10 d, and at the same time add electrolytic multivitamins to the drinking water; after 3 d the whole herd can recover to health.

5.4 For persistent high fever, Yada Ke Re Kuai injection and Bencao Shengzhen injection can be used, 1 vial each per 50 kg body weight, injected separately, twice daily.

5.5 The traditional Chinese medicine preparation Fangfeng Baidu San has a special effect in preventing swine influenza and can be used according to the instructions and in light of actual conditions.

5.6 For pigs with a relatively severe course of swine influenza, Daqingye and Chaihu injections should be supplemented, with good results. Amantadine injection can also be used. To prevent secondary infection, antibiotics should be used simultaneously.