Glässer Disease Respiratory Form in Pigs

Glässer disease is an infectious bacterial disease of pigs caused by Glaesserella parasuis. You may also see the older name Haemophilus parasuis. This organism commonly lives in the upper respiratory tract of healthy pigs, so its presence alone does not always mean disease. Problems start when the bacteria move beyond the airway and spread through the body.

In the respiratory form, piglets or growing pigs may first show dyspnea, abdominal breathing, weakness, and fever. Some pigs also develop fibrinous pleuritis or bronchopneumonia, which can make breathing look hard and painful. Even when breathing signs are the most obvious problem, Glässer disease is usually considered a systemic disease, not only a lung disease.

Many affected pigs also have inflammation around the lungs, heart, abdomen, joints, or brain. That is why respiratory signs may appear alongside lameness, swollen joints, reluctance to move, tremors, paddling, or sudden death. The course can be peracute, acute, or chronic, and chronic survivors may grow poorly because of scar tissue in the chest or abdomen.

This is a condition where early veterinary involvement matters. A pig that looks mildly off in the morning can become severely ill later the same day, especially after weaning, transport, regrouping, or another respiratory infection.

Glaesserella parasuis is the direct cause. The tricky part is that this bacterium is also a normal colonizer of the upper respiratory tract in many pigs. Disease usually happens when a virulent strain gains access to the bloodstream and body cavities, or when the pig's normal defenses are weakened.

Common triggers include weaning stress, mixing groups, transport, crowding, poor ventilation, temperature swings, and concurrent infections such as PRRS or porcine circovirus 2-associated disease. These stressors can damage respiratory defenses or increase bacterial spread between pigs.

Age matters too. Young pigs, especially around or after weaning, are often the most vulnerable because maternal immunity is changing and social or environmental stress is high. Herds may also have different serovars or strains present, which can make control harder.

Because the organism can be present in healthy pigs, finding it in the nose or upper airway does not prove it is the cause of illness. Your vet has to interpret signs, lesions, herd history, and sample location together.

Diagnosis starts with a farm history and physical exam. Your vet will look at age group, recent stressors, vaccination history, death loss pattern, and whether pigs have breathing trouble alone or also show lameness, fever, or neurologic signs. In Glässer disease, the combination of respiratory distress with evidence of systemic inflammation is an important clue.

Testing is most useful when samples come from systemic sites in untreated, clinically affected pigs. Your vet may collect samples from pleura, pericardium, peritoneum, joints, brain, or other affected tissues for culture or PCR. This matters because G. parasuis is commonly found in the upper airway, so nasal or routine respiratory samples may not confirm true systemic disease.

Necropsy can be especially helpful in herd outbreaks. Typical findings may include fibrinous pleuritis, pericarditis, peritonitis, polyarthritis, or meningitis, sometimes with increased fluid in body cavities. Some pigs with severe signs may have few obvious gross lesions, especially in very rapid cases.

Your vet may also test for other respiratory or systemic diseases that can look similar or occur at the same time. That can include PRRS, circovirus-associated disease, Streptococcus suis, Mycoplasma hyopneumoniae, or other bacterial pneumonias. A practical diagnosis often combines clinical pattern, lesions, and laboratory confirmation.

Prevention focuses on lowering stress and reducing the chance that Glaesserella parasuis will move from the airway into the rest of the body. Good basics matter: stable temperatures, clean air, appropriate stocking density, careful ventilation, clean water access, and minimizing unnecessary mixing or transport stress around weaning.

Work with your vet on a herd-specific plan. That may include reviewing pig flow, all-in/all-out practices, quarantine for incoming pigs, and control of other respiratory diseases such as PRRS or circovirus-associated problems. Because coinfections and management stress often set the stage for outbreaks, prevention is rarely about one step alone.

Vaccination can be part of prevention. Both commercial and autogenous vaccines are used, but protection can vary because different serovars and strains do not all cross-protect well. Your vet may recommend vaccine changes based on herd history and diagnostic results rather than using a one-size-fits-all approach.

If you keep a pet pig rather than a production herd, the same principles still apply. Avoid abrupt environmental changes, reduce contact with unfamiliar pigs of unknown health status, and call your vet early for fever, breathing changes, or sudden lameness. Early action is often the most practical prevention tool once a problem starts.