When the weather turns cold, many pig farms take the easy route: they shut the doors and windows and lower the curtains. The pig houses get warmer, but then the pigs start getting sick.
First come coughing and labored breathing, followed by fever and loss of appetite. In severe cases, pigs lie motionless, gasping with their mouths open, with bloody foam coming from the corners of their mouths and their noses. Often, they are still eating feed one day, but are stiff by the next morning.
This is not African swine fever, nor is it ordinary respiratory disease. It is porcine contagious pleuropneumonia, commonly abbreviated as “CCPP.” It is one of the acute respiratory diseases most likely to emerge on pig farms after barns are closed up for autumn and winter. Growing and finishing pigs are most susceptible, and the disease spreads quickly and can cause rapid death.
This year, the Ministry of Agriculture and Rural Affairs also specifically listed it as a disease requiring priority prevention and control in its technical guidelines for preventing and controlling swine diseases in autumn and winter. Today, we’ll explain the disease clearly: how to recognize it, how to treat it, and how to prevent it.
Actinobacillus pleuropneumoniae most often targets medium-to-large finishing pigs that grow quickly and are raised at high stocking densities.
I. What exactly is this disease?
The pathogen that causes pleuropneumonia is a bacterium called Actinobacillus pleuropneumoniae, which mainly lives in the respiratory tract of pigs. It has several characteristics that pig farmers should be aware of:
It particularly affects medium-to-large pigs. Pigs can be affected after weaning, but it is most common and severe in medium-to-large pigs during the fattening stage, especially fast-growing commercial pigs raised at high stocking densities. This differs from many diseases that “particularly affect young piglets”—the more intensively a group of pigs is fattened, the more vigilant you should be.
It is most prevalent in autumn and winter and during seasonal transitions. A sharp drop in temperature, large day–night temperature differences, and cold, damp conditions are the most direct triggers. There was a real case at a pig farm this year: a cold wave hit and temperatures dropped sharply; ventilation in the pig housing did not keep up, and as ammonia levels rose, finishing pigs quickly developed difficulty breathing and died acutely.
Disease occurs conditionally; “sealing off the pen” is the trigger. Many pig farms already have this bacterium in their herds, where it usually causes no problems. Once stocking density is too high, ventilation is poor, ammonia and dust levels are too high, or temperature fluctuations cause stress, the pigs’ resistance drops, and the bacterium takes advantage. So this disease is often not “brought in” but “brought on by stuffiness and cold.”
Spreads quickly. It is transmitted between pigs mainly through droplets produced when sick pigs and carrier pigs cough or breathe heavily. If one or two pigs in a pen are affected, it can spread to adjacent pens within a few days.
Two. How to recognize it: remember these typical signs
Based on the speed of onset, swine pleuropneumonia is mainly classified into three forms: peracute, acute, and chronic, which differ considerably in their signs.
Peracute form—the most severe, mainly causing sudden death. Affected pigs suddenly develop a high fever above 41℃, become extremely lethargic, stop eating, and may have mild diarrhea or vomiting. In the later stages, their heartbeat speeds up, and the skin around the mouth and ears and on the limbs turns bluish-purple (cyanotic). They breathe with their mouths open while sitting like a dog (the dog-sitting posture). Before death or after death, blood-tinged, frothy discharge flows from the mouth and nose. There is often no time to treat them; they die within one to two days. Some show no obvious signs on the first day and are found dead in the pen the next.
Acute form—coughing, wheezing, and fever, with a considerable mortality rate. Body temperature 40.5–41°C; coughing and labored breathing are pronounced, and some animals show abdominal breathing. Feed intake is reduced or stops altogether. If not treated promptly, death may occur 2–4 days after onset; survivors are prone to developing the chronic form.
Chronic form—slow growth and recurrent coughing. It is more common in the later stages of an outbreak. Affected pigs cough intermittently, lose condition, and grow slowly, with a markedly worsened feed-to-meat ratio. Symptoms are usually mild, but further stress or infection with another pathogen may aggravate the condition and even lead to acute death.
The postmortem findings are typical: the lungs are congested, hemorrhagic, and edematous, and pale red or yellow exudate accumulates in the thoracic cavity. In cases with a somewhat longer course, the lungs adhere to the chest wall and pericardium, and a layer of fibrin-like membrane can be seen on the lung surface.
Three: Key point: Don’t confuse it with these two diseases
There is more than one disease that causes coughing and wheezing in autumn and winter. Misidentifying it or taking the wrong approach wastes life-saving time.
Distinguish it from swine pasteurellosis (Pasteurella multocida). Both can cause high fever, difficulty breathing, swelling of the throat or neck, and purplish skin. Swine pasteurellosis commonly causes redness, swelling, heat, and pain around the throat and neck, and is commonly known as “throat-locking wind.” It is very difficult to distinguish the two with the naked eye alone; confirmation requires laboratory pathogen isolation or PCR.
Differentiate it from mycoplasmal pneumonia (enzootic pneumonia). Mycoplasma infection mainly causes a persistent dry cough and slow growth; it generally does not cause much high fever and rarely leads to sudden, large-scale deaths. APP, by contrast, causes sudden high fever, labored breathing, blood-tinged foam from the nose and mouth, and acute death, with a much more sudden onset. Clinically, however, the two often occur together.
Respiratory diseases in autumn and winter rarely occur “on their own.” APP often occurs in mixed infections or as a secondary infection alongside PRRS, mycoplasma, swine erysipelas, swine influenza, and other diseases. If pigs develop sudden deaths, blood-tinged foam from the nose and mouth, or open-mouth, dog-sitting breathing, strongly suspect APP. However, do not rush to a conclusion yourself. Have a licensed veterinarian examine the pigs as soon as possible, confirm the diagnosis using necropsy and laboratory testing, and then determine a course of action.
Early detection and early isolation: When you find a suspicious pig, consider that the entire pen or barn may already be carrying the bacteria.
IV. What should you do when disease breaks out in the herd?
Swine enzootic pneumonia is a bacterial disease, and antibiotics are effective against it—but there is one major condition: treatment must start early, be accurate, and last for a sufficient course. The most acute cases often die before the medication takes effect. So when you find one suspected pig, consider that all pigs in the same pen or barn may already be carrying the bacteria.
Step one: Isolate sick pigs and treat the entire group.
Separate the pigs with obvious symptoms and place them in an individual pen downwind for care. For pigs in the same group or barn that have not yet become ill or have mild symptoms, administer preventive medication to the entire group under veterinary guidance; do not treat only the few pigs with visible symptoms. Combine injections with medication mixed into feed or drinking water: inject severely ill pigs, and administer medication to groups that can eat feed.
Step two, choose the right antimicrobial; ideally, perform a susceptibility test first.
Commonly used effective drugs include ceftiofur, florfenicol, tilmicosin, tylosin, amoxicillin, enrofloxacin, and oxytetracycline, among others. However, note that:
· Drug resistance has become increasingly common after long-term medication for Glässer’s disease on many pig farms. Susceptibility to different drugs varies greatly between farms and serotypes. If possible, collect samples for antimicrobial susceptibility testing and choose drugs based on the results; don’t keep using the same old treatment year after year.
· Use the full dose for the full course, generally for 5 to 7 days. Don’t stop as soon as the animal seems better, or the disease may recur or become chronic, and drug resistance may worsen.
· Do not use medications with the same mechanism of action repeatedly over a long period; rotate them under veterinary guidance.
Step three, improve the environment immediately and “remove the triggers” while treating.
Relying only on medication without changing the environment is like putting out a fire while pouring oil on it. After the disease occurs: improve ventilation and air exchange, and remove ammonia and stale air as quickly as possible while maintaining the required temperature; reduce stocking density and relocate animals wherever possible; keep conditions dry, clean up manure promptly, and avoid high humidity and low temperatures; reduce stressors such as moving animals between groups, combining pens, and frightening them.
Step four: Dispose of carcasses safely and disinfect thoroughly.
Dead and culled pigs must be disposed of harmlessly in accordance with regulations. Never discard them improperly or slaughter and sell them without authorization. Thoroughly clean and disinfect sick pigs’ excrement, contaminated pens, and equipment. Keep personnel and tools as consistent as possible, and change shoes and disinfect when moving between pens to avoid carrying pathogens into healthy pigs’ pens.
Medication safety red line: All of the above are prescription drugs. The specific medication, dosage, and course of treatment must be determined by a licensed veterinarian based on the confirmed diagnosis, the pigs’ body weight, and the instructions for the current batch, and the withdrawal period must be strictly observed. Special reminder: Tilmicosin may only be administered to pigs orally (mixed into feed); it must not be injected intramuscularly. Intramuscular injection of tilmicosin in pigs carries a risk of acute cardiovascular poisoning and death, so never inject it just to save time.
Windows must not be sealed completely: the negative-pressure fan on the gable wall is key to exhausting ammonia and bringing in fresh air in autumn and winter.
Five. How to prevent it: take these steps before sealing the windows for insulation.
For a disease like infectious pleuropneumonia, which is “opportunistic,” prevention boils down to one thing: don’t create the conditions for it to take hold.
First, get both insulation and ventilation right. This is the most important issue in autumn and winter—and the one most prone to extremes. The right approach is “maintain warmth without forgetting ventilation”: when daytime temperatures are higher, open windows or run fans at appropriate times to exchange air, making good use of the window of opportunity around midday. Where available, use equipment such as variable-frequency fans, positive-pressure air supply, or hot-air furnaces to retain heat while expelling ammonia and moisture. The standard is simple: when entering the pig house, people should not find the air pungent, irritating to the eyes, or stuffy; the pigs should sleep soundly, and respiratory diseases will be reduced considerably.
Second, control stocking density and use an all-in, all-out system. In autumn and winter, do not keep pigs at excessive stocking densities just because you are worried about the cold. Stick to an all-in, all-out system: after a batch of pigs is shipped, thoroughly clean and disinfect the pens, then leave them empty for a period before bringing in new pigs. This can significantly interrupt the cycle of pathogens.
Third, reduce stress from temperature fluctuations. Check the weather forecast. Before a cold snap or temperature drop arrives, repair the housing and hang curtains to seal gaps, but leave adjustable ventilation openings. Provide extra care before and after weaning and group transfers. If necessary, provide stage-specific preventive care under a veterinarian’s guidance.
Fourth, make good use of vaccines. Commercial vaccines for contagious pleuropneumonia are available, including inactivated vaccines for locally prevalent serotypes. For pig farms with severe contamination and repeated outbreaks, vaccination can be scheduled under veterinary guidance, with a focus on protecting pigs during the finishing stage. The specific program should be determined based on the serotypes circulating on the farm, because contagious pleuropneumonia has many serotypes; if the vaccine strain does not match, protection may be reduced.
Fifth, manage introductions and biosecurity. Maintain a closed-herd system; when introducing pigs is necessary, source them from negative, healthy farms, then quarantine and observe them after arrival and test them before introducing them into the herd. Routinely disinfect personnel, vehicles, and supplies to prevent the disease from being brought in.
A final note
Porcine contagious pleuropneumonia has a cumbersome name, but the principle is simple: when it gets cold and the pig housing is closed up, focusing only on keeping it warm without providing ventilation stresses the pigs, and the bacteria lurking in the background can become deadly.
It comes on quickly and kills quickly. The most acute cases often leave you no chance to treat the pigs. So what really works has never been to wait until pigs go down and then search the whole barn for medicine. Instead, get ventilation, stocking density, and temperature differences sorted out before closing the windows and keeping the barn warm, and combine this with vaccination to detect, diagnose, and treat early. May your pig barns stay warm but not stuffy this autumn and winter, and may your pigs grow quickly and stay healthy.