Porcine pleuropneumonia is a highly contagious respiratory disease caused by Actinobacillus pleuropneumoniae. It most commonly affects pigs in the growing and fattening stages. The predominant serotypes are 1, 2, 3 and 7. The acute form may cause severe respiratory distress and sudden death. Its pathological features include pleuritis and hemorrhagic necrotizing pneumonia. Toxins produced by the pathogen can kill macrophages and neutrophils, thereby reducing the body's resistance.

 

 

I. Clinical features

 

Affected pigs mainly show respiratory distress, with abdominal breathing and paroxysmal coughing. Before death, blood-tinged, foamy secretions may flow from the mouth and nose.

 

Pathological changes are mainly found in the thoracic cavity and lungs. Pneumonic lesions are mostly bilateral, clearly demarcated from normal tissue, and present as fibrinous pleuropneumonia. Fibrinous pleuropneumonia may spread throughout the lungs, causing the lungs to adhere to the pleura, making it difficult to separate them.

 

II. Diagnostic methods

 

Collect necrotic lung tissue from a pig that died of the disease and inoculate it aseptically onto a chocolate agar plate or an agar medium containing sheep blood and Staphylococcus aureus. Incubate overnight at 5% carbon dioxide and 37℃. If small hemolytic colonies are observed, together with a positive CAMP reaction and satellite growth, and a positive urease test, the isolate can be identified as a biotype I strain of Actinobacillus pleuropneumoniae.

 

Regarding antimicrobial susceptibility, Actinobacillus pleuropneumoniae is susceptible to tetracycline, streptomycin, florfenicol, tilmicosin, and other drugs. Actual medication should be based on susceptibility test results and veterinary guidance; indiscriminate use should be avoided.

 

Three. Prevention and control measures

 

Block transmission, eliminate predisposing factors, implement precision immunization, and use medication scientifically.” A single measure is unlikely to be effective; a systematic prevention and control system must be established.

 

1, Build a strong biosecurity barrier (block pathogen entry)

 

Strict breeding-stock introduction management: maintain a closed herd by breeding and raising replacements on site. When introducing pigs is necessary, they should come from areas free of the disease and farms with no history of contagious pleuropneumonia. After new pigs arrive, they must be kept in an off-site quarantine facility for at least 4 weeks. During this period, conduct serological testing; they may be mixed with the herd only after testing negative.

 

Strictly control personnel and vehicles: All vehicles entering the site (especially pig transport trucks and feed trucks) must be thoroughly cleaned, disinfected, and dried. Personnel must strictly follow bathing, changing clothes, and disinfection procedures.

 

Cut off indirect transmission: Implement bird, rodent, and insect control on the pig farm. These animals can mechanically carry pathogens.

 

2, Optimize feeding management (eliminate factors that trigger disease)

 

Implement all-in/all-out management: Pigs in the same building or batch must enter and leave at the same time. After the pigs are shipped out, thoroughly clean and disinfect the building, then leave it empty for at least 14 days to cut off cyclical infection.

 

Control stocking density: Avoid overcrowding and ensure each pig has sufficient space to move around. Density is a factor affecting the rate of disease transmission.

 

Improve environmental conditions:

 

Ventilation and insulation: Maintain air circulation to reduce the concentration of harmful gases such as ammonia and hydrogen sulfide, while avoiding direct drafts. Pay attention to temperature fluctuations in autumn, winter, and early spring to prevent cold and heat stress.

 

Temperature and humidity control: Maintain suitable humidity, and clean manure regularly to reduce pathogen growth.

 

Reduce stress: During periods such as herd transfers, vaccination, or sudden weather changes, anti-stress substances such as electrolytes, multivitamins, and vitamin C can be added to drinking water or feed.

 

3, vaccines are an economical and effective preventive measure,

 

Vaccine selection: This disease has many serotypes ( 18 known types), with weak cross-protection between types. Laboratory testing must be used to identify the predominant serotypes circulating on the farm, and a multivalent inactivated vaccine or genetically engineered vaccine containing the corresponding serotypes should be selected. Blind vaccination may be ineffective.

 

Immunization schedule:

 

Sows: Immunize 4-6 weeks before farrowing to provide piglets with maternal antibodies.

 

Piglets: The first immunization is usually given at 5-8 weeks of age, followed by a booster 2-3 weeks later.

 

Breeding boars: Give a booster immunization once every six months.

 

Fattening pigs: Booster immunization before the age at which disease risk is high (for example, at 12-14 weeks of age) is essential.

 

Immunity monitoring: Antibody levels can be tested by sampling 3-4 weeks after immunization to assess the effectiveness and uniformity of the immunization.

 

For porcine contagious pleuropneumonia, vaccination with a multivalent inactivated vaccine is generally used for prevention.

 

Four. Standardized drug prevention and control (controlling clinical cases)

 

Drug prevention: During high-risk periods such as weaning, transfer between groups, or seasonal changes, or when there is an outbreak nearby, sensitive drugs can be added to feed or drinking water for short-term group prevention. Commonly used drugs include tilmicosin, florfenicol, tiamulin, and doxycycline.

 

Emergency treatment:

 

Principle: Early detection, early isolation, and early treatment. Treat pigs housed in the same pen as potentially infected, and provide preventive treatment to the group.

 

Medication selection: It is strongly recommended to perform an antimicrobial susceptibility test first and select the drug to which the animals at this farm are most susceptible. Commonly used effective drugs include ceftiofur, florfenicol, and enrofloxacin.

 

Administration: Give injectable medication as a priority to severely ill pigs (not eating or drinking, or having difficulty breathing). For mildly ill pigs or group prevention, medication may be administered in feed or drinking water.

 

Complete the full course of treatment even after symptoms disappear to prevent pigs from becoming chronic carriers.

 

Symptomatic treatment: Antipyretic and analgesic drugs (such as flunixin meglumine), bronchodilators (such as aminophylline), and traditional Chinese medicine preparations may be used in combination to relieve symptoms.

 

V. Regular Monitoring and Eradication (Eliminating the Source of Infection)

 

Serological monitoring: Conduct serological testing of the pig herd regularly (for example, every six months) to assess infection status.

 

Cull positive pigs: Positively tested boars and sows, as well as pigs with chronic coughing or stunted growth, should be firmly culled to cleanse the herd.

 

Harmless disposal: Dead pigs and contaminated materials must be strictly disposed of harmlessly, such as by deep burial or incineration, in accordance with regulations. Arbitrary discarding is strictly prohibited.

 

Cleanse the herd: Conduct regular monitoring and cull positive and chronically carrier pigs.

 

Summary

 

Porcine contagious pleuropneumonia occurs most often in growing and finishing pigs. The acute form carries a high risk of death. Typical signs include difficulty breathing, abdominal breathing, paroxysmal coughing, and bloody, frothy discharge. Fibrinous pleuropneumonia may be observed on pathological examination. Laboratory diagnosis may combine isolation on a specific culture medium, the CAMP test, satellite growth phenomenon, and urease test. Prevention and control should emphasize vaccination with multivalent inactivated vaccines, together with standardized diagnosis and the judicious use of medication.

 

Important reminder: This disease often occurs as a mixed infection with porcine reproductive and respiratory syndrome, circovirus, Mycoplasma, and other pathogens, forming “porcine respiratory disease complex.” Prevention and control require a coordinated, integrated approach. No single measure can replace systematic biosecurity and health management.