Symptoms and Diagnosis and Treatment Methods of Swine Infectious Pleuropneumonia
What are the symptoms of swine infectious pleuropneumonia? How is it diagnosed and treated?
Actinobacillus pleuropneumoniae is a Gram-negative small ball-rod-shaped bacterium. This bacterium is a facultative anaerobe and has weak resistance to the external environment, and ordinary disinfectants can kill it. Sick pigs and carrier pigs are the source of infection of this disease. Breeding boars and chronically infected pigs play a very important role in spreading this disease, which is mainly transmitted through airborne droplets. After the pathogen is discharged through breathing, coughing, sneezing and other routes, it forms droplets and is transmitted through the respiratory tract by direct contact. It can also be transmitted through indirect contact with vehicles, equipment and clothing of keepers contaminated by the pathogen.
Pigs of all ages and sexes are susceptible, with pigs aged 6 weeks to 6 months being more commonly affected, but 3-month-old piglets are the most susceptible. The occurrence of this disease mostly presents as a peracute or acute course and causes rapid death. In acutely outbreaks herds, the morbidity and mortality rates are generally around 50%; the mortality rate of the peracute type can reach 80%-100%.
The occurrence of this disease has obvious seasonality, mostly occurring from April to May and from September to November. Stress factors such as sudden changes in the feeding environment, transfer or mixing of pig herds, crowding or long-distance transport, poor ventilation, excessively high humidity, and sudden temperature changes can all cause the occurrence of this disease or accelerate its spread, increasing the morbidity and mortality rates.
The disease can be divided into peracute, acute and chronic types. The peracute type occurs suddenly, with the sick pig's body temperature rising to 41°C-42°C, increased heart rate, depression, loss of appetite, and short-term diarrhea and vomiting symptoms. In the early stage, sick pigs have no obvious respiratory symptoms; in the later stage, there is heart failure, cyanosis of the nose, ears, eyes and hindquarters skin, extreme difficulty breathing in the late stage, often standing still or in a dog-sitting posture, opening the mouth and protruding the tongue, coughing and wheezing, and abdominal breathing. Before death, the body temperature drops, and in severe cases, foamy bloody secretions flow from the mouth and nose. Sick pigs die within 24 hours to 36 hours after the appearance of clinical symptoms. Some cases die suddenly without any clinical symptoms. The mortality rate of this type is as high as 80%-100%. In the acute type, the sick pig's body temperature rises to 40.5°C-41°C, with severe difficulty breathing, coughing, heart failure, reddening of the skin, and depression. Due to differences in feeding management and other stress conditions, the course of the disease varies in length. The chronic type mostly appears in the later stage of the acute phase. Sick pigs have slight fever or no fever, with body temperature at 39.5°C-40°C, poor spirits, and reduced appetite. There is spontaneous or intermittent coughing of varying degrees, abnormal breathing, and stunted growth. The course of the disease ranges from a few days to 1 week, and the pigs may recover or, when stress conditions appear, the symptoms worsen, the pig's whole body muscles become pale, the heartbeat speeds up, and sudden death occurs.
Different disease conditions present different dissection symptoms. In peracute-type dead pigs, necropsy shows that the trachea and bronchi are filled with foamy bloody secretions, the lungs are congested, hemorrhagic, and fibrinous thrombi form in the blood vessels, there is alveolar and interstitial edema, and inflammation appears in the anterior lower part of the lungs. In pigs that die in the acute phase of the acute type, obvious necropsy lesions can be seen: the throat is filled with blood-like fluid, bilateral pneumonia, with lesions often appearing in the cardiac lobe, apical lobe and diaphragmatic lobe; the lesion areas are purplish red, firm, and clearly outlined, and blood-colored gelatinous fluid accumulates in the pulmonary interstitium. In the chronic type, nodules of varying sizes can be seen on the lungs (nodules often occur in the diaphragmatic lobe), surrounded by relatively thick connective tissue, and bleeding points can be seen in the pericardium.
When the pig herd is affected, treatmentshould be carried out on the principle of relieving difficulty breathing and providing antibacterial therapy, and sufficient doses of antibiotics should be used with a sufficiently long course of treatment. Earlytreatmentof this disease can achieve relatively good results, but antibacterial drugs should be selected based on the results of drug sensitivity testing. Generally, doxycycline, tiamulin, sulfonamides, etc. can be used. Injection administration has a better effect on affected pigs, and antibiotics can be added to the feed to control the condition. Although antibiotics can reduce the mortality rate, pigs treated withtreatmentare often carrier pigs. Drugtreatmentis not ideal for chronic-type sick pigs.
For this disease, feeding management should first be strengthened, strict hygiene and disinfection measures should be implemented, attention should be paid to ventilation, and the air in the barn should be kept fresh. The effects of various stress factors should be reduced, and a sufficiently balanced nutritional level for the pig herd should be maintained. Regular health care for the pig herd should be carried out to achieve the purpose of purifying the pig herd and improving the resistance of the pigs.