Actinobacillus Pleuropneumonia in Pigs: Sudden Severe Pneumonia and Death
- See your vet immediately. Actinobacillus pleuropneumonia is a fast-moving, contagious bacterial lung infection in pigs that can cause severe breathing distress and sudden death within hours.
- Common warning signs include fever, reluctance to move, hard or open-mouth breathing, blue or darkened skin from low oxygen, and frothy or blood-tinged discharge from the nose or mouth.
- Recovered pigs may remain carriers, so one sick pig can signal a herd problem that needs rapid isolation, testing, and a herd-level plan with your vet.
- Early treatment can help some pigs, but severely affected animals may still die despite care. Necropsy and lab testing are often important for confirming the cause and guiding control.
What Is Actinobacillus Pleuropneumonia in Pigs?
Actinobacillus pleuropneumonia, often shortened to APP, is a severe bacterial respiratory disease caused by Actinobacillus pleuropneumoniae. It mainly affects young growing pigs, but adults can also become sick during a new outbreak. The disease is known for its sudden onset, short course, and high death loss when pigs are not treated quickly. (msdvetmanual.com)
This infection causes a damaging pleuropneumonia, meaning inflammation of both the lungs and the lining around the lungs. In acute cases, pigs can go from looking normal to being in extreme respiratory distress within hours. Some are found dead before obvious signs are noticed. Survivors may develop chronic lung damage, poor growth, and ongoing respiratory problems. (msdvetmanual.com)
APP spreads mainly through close pig-to-pig contact, especially nose-to-nose contact. Recovered pigs can remain carriers, which makes control challenging in group housing, breeding herds, and any setting where pigs are mixed or moved. (msdvetmanual.com)
Symptoms of Actinobacillus Pleuropneumonia in Pigs
- Sudden death with few or no warning signs
- Severe breathing distress or "thumping" respirations
- Open-mouth breathing
- Fever, often up to 107°F (41.5°C)
- Reluctance to move, weakness, or collapse
- Loss of appetite
- Frothy, sometimes blood-stained discharge from the nose or mouth
- Blue, purple, or darkened skin from poor oxygenation
- Coughing or poor growth in chronic survivors
See your vet immediately if any pig has hard breathing, open-mouth breathing, blue or darkened skin, bloody foam from the nose or mouth, or if pigs are being found dead suddenly. APP can spread quickly through a group, and the sickest pigs may decline within hours. Even if one pig seems only mildly affected, a herd-level response may be needed because apparently recovered pigs can continue to carry the bacteria. (msdvetmanual.com)
What Causes Actinobacillus Pleuropneumonia in Pigs?
The cause is infection with the bacterium Actinobacillus pleuropneumoniae. In the United States, serotypes 1, 5, and 7 have historically been common. The bacteria spread mainly by close contact between pigs, especially nose-to-nose contact. Aerosol spread appears to be more limited, but it can still matter in some housing situations. (msdvetmanual.com)
A major challenge is that pigs that recover may remain carriers, often harboring the organism in the upper respiratory tract or tonsils. Those carrier pigs can introduce infection into a new group or trigger disease when pigs are mixed, transported, crowded, or otherwise stressed. (msdvetmanual.com)
Outbreak risk tends to rise when there is poor ventilation, frequent mixing of pigs from different sources, inadequate quarantine, or other respiratory disease pressure in the herd. APP may also be part of a broader porcine respiratory disease picture, where multiple pathogens and management stressors make lung disease more severe. (merckvetmanual.com)
How Is Actinobacillus Pleuropneumonia in Pigs Diagnosed?
Your vet will usually start with the history and the pattern of disease in the group. Sudden onset, severe breathing distress, fever, rapid spread in previously unaffected pigs, and sudden deaths all raise concern for APP. Because several swine respiratory diseases can look similar early on, diagnosis should not rely on signs alone. (msdvetmanual.com)
Confirmation is typically based on bacterial culture or other laboratory testing from appropriate samples. In pigs that die or are euthanized, necropsy can be especially helpful because APP often causes dramatic lung and pleural lesions, including fibrin, hemorrhage, adhesions, and areas of necrosis. Fresh lung tissue from affected areas is commonly used for testing, and your vet may also recommend PCR or serotyping depending on the herd situation. (msdvetmanual.com)
Diagnosis is not only about naming the bacteria. It also helps your vet choose practical control steps, such as isolation, medication strategy, vaccination planning, and whether breeding animals or incoming pigs may be acting as carriers. (msdvetmanual.com)
Treatment Options for Actinobacillus Pleuropneumonia in Pigs
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent exam or farm call with isolation of affected pigs
- Early injectable or water/feed medication selected by your vet based on likely bacterial pneumonia patterns and farm regulations
- Anti-inflammatory or fever-reducing support if appropriate
- Improved airflow, reduced handling stress, easy access to water, and close monitoring of pen-mates
- Basic necropsy of a freshly dead pig if available to guide next steps
Recommended Standard Treatment
- Prompt veterinary exam with treatment of sick pigs and rapid separation from healthy groups
- Targeted diagnostics such as necropsy, bacterial culture, and/or PCR from lung tissue or respiratory samples
- Medication plan for affected pigs and exposed pen-mates when your vet determines it is appropriate
- Review of ventilation, stocking density, pig flow, quarantine, and mixing practices
- Written herd-control plan that may include vaccination, monitoring, and carrier-risk management
Advanced / Critical Care
- Hospital-level monitoring or intensive on-farm critical care directed by your vet
- Oxygen support where available, repeated injectable medications, and aggressive supportive care
- Expanded diagnostics, including culture/PCR, serotyping, and broader respiratory disease investigation
- Detailed herd epidemiology review for source tracing, carrier control, and long-term prevention
- Follow-up imaging or postmortem evaluation in complicated or high-value cases
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Actinobacillus Pleuropneumonia in Pigs
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look most consistent with APP, or are other respiratory diseases also likely?
- Which pigs should be isolated right now, and how should I handle exposed pen-mates?
- What samples would give the best chance of confirming the diagnosis in this herd?
- If a pig dies, should we arrange a necropsy right away, and how should the body be stored until then?
- What treatment options fit my goals and budget for this pig or herd?
- Are recovered pigs likely to remain carriers, and what does that mean for future mixing or breeding?
- Would vaccination make sense for my pigs, and if so, what schedule is appropriate?
- What housing, ventilation, or biosecurity changes would most reduce the chance of another outbreak?
How to Prevent Actinobacillus Pleuropneumonia in Pigs
Prevention focuses on keeping APP out of the group and reducing the chance that carrier pigs spread it. Work with your vet on quarantine for new arrivals, limiting contact between pigs from different sources, and avoiding unnecessary mixing. Because recovered pigs may remain carriers, herd history matters a great deal when choosing breeding stock or replacement animals. (msdvetmanual.com)
Good air quality and low-stress management also matter. Ventilation, stocking density, transport stress, and abrupt regrouping can all influence how severe respiratory disease becomes. A practical prevention plan often includes better pig flow, careful observation after movement or weaning, and fast separation of any pig showing fever or breathing changes. (merckvetmanual.com)
Vaccination may be part of prevention in some settings. Merck Veterinary Manual lists APP vaccination for pet pigs beginning at 8 to 12 weeks of age, repeated in 3 to 4 weeks, with semiannual or annual boosters, but the right program depends on the pig's risk, age, and local disease pressure. Your vet can help decide whether vaccination, monitoring, or herd elimination strategies make the most sense for your situation. (merckvetmanual.com)