The definition of pneumonia is inflammation of the lungs caused by an infection. Cats are much less commonly afflicted with pneumonia than dogs. In fact, pneumonia in cats is rare!
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Pneumonia in cats
In most species, pneumonia is caused by a bacterial lung infection. However, in cats, viral pneumonia is much more common. All young cats with unexplained pneumonia are assumed first to have a viral cause of pneumonia before other causes.
Upper respiratory tract infections are frequently shared between cats. Pneumonia is much less common in cats. However, there are rare reports of severe pneumonia outbreaks amongst groups of feral or shelter cats. If your cat has pneumonia, it would be safest to consider them contagious to any other cat in the home.
Infectious causes of pneumonia in cats
Besides bacterial and viral infections, other infectious causes of pneumonia are fungal, protozoal and parasitic causes.
If a cat develops pneumonia they often require hospitalization to aid recovery. Treatment for pneumonia typically entails antibiotic therapy, intravenous fluid administration to support their hydration to improve lung function and sometimes supplemental oxygen. The average hospital stay to treat a cat with pneumonia is generally between 3 to 5 days.
Symptoms of feline pneumonia
Symptoms of pneumonia in cats are: fever, lethargy, decreased appetite and increased respiratory rate and effort. Diagnosis of pneumonia relies on chest x-rays that demonstrate infiltrates within the lungs. On x-rays of the chest, bacterial pneumonia tends to have alveolar infiltrates (fluffy patches surrounding the airways) while other causes can produce a more nodular to diffuse pattern.
Determining the infection causing pneumonia in cats
Deducing the underlying cause of pneumonia typically requires a sample of fluid from the lungs. This fluid can be collected during a sedated procedure called a bronchoalveolar lavage or a transtracheal wash. A bronchoalveolar lavage involves instilling a small volume of sterile saline into the lungs. The fluid “washes the lungs” and is then retrieved and submitted for a bacterial culture. The bacterial culture will identify any bacteria colonizing the lungs and determine what antibiotics will work to treat the infection.
Feline upper respiratory panel for infectious airway disease
Upper respiratory swabs can be submitted to a reference lab for a PCR test to look for a variety of possible upper respiratory tract pathogens. While this only examines the upper airways, it can help to infer what may be affecting the lower airways, particularly if a airway lavage sample is negative for growth of bacteria.
Idexx is a frequently utilized veterinary reference lab. Their feline upper respiratory PCR panel tests for the following bacteria and viruses :
Bacteria: Bordetella bronchiseptica, Chlamydophila felis and Mycoplasma felis.
Viruses: feline calicivirus, feline herpes virus type 1, and 4 influenza viruses.
Bacterial pneumonias in cats are typically gram negative bacteria such as e coli, pasteurella, bordetella bronchiseptica and mycoplasma.
Feline viral pneumonia
Viral causes of feline pneumonia can include calicivirus, herpes virus and influenza viruses Feline herpesvirus and calicivirus are the most frequent causes of upper airway infections characterized by sneezing and nasal congestion. Herpes virus can cause corneal eye ulcers and calicivirus can cause lingual and oral ulceration. Both rarely cause lower airway pneumonia. The core feline vaccination, Feline Rhinotracheitis, Calicivirus, Panleukopenia vaccine (FVRCP) helps to protect against both these viruses. While it will not prevent infection it does significantly reduce severity of disease.
To learn more at cat upper respiratory infections (colds) read this resource:
Feline fungal pneumonia
Fungal causes of pneumonia are not common at all. They are most often found in parts of the country where these infections are endemic. In cats cryptococcus and aspergillus are the most common suspects.
Fungal infections causing pneumonia in cats is rare, but concurrent diabetes mellitus was found to be a risk factor for cats that did test positive for fungal pneumonia. The most common fungal infections contributing to fungal pneumonia are aspergillus and cryptococcus. Unfortunately most cats will not survive an aspergillosis fungal pneumonia. Cryptococcus is the most common systemic fungal infection in cats. It is acquired when a cat inhales the spores of the organisms, most often found in pigeon droppings or decaying vegetation. Cryptococcus rarely causes pneumonia. Rather, it is known to cause nasal infections and sometimes skin infection.
Toxoplasmosis causing pneumonia in cats
By far the most common protozoal cause of pneumonia in cats is disseminated toxoplasmosis. Cats that have compromised immune function are at increased risk. This includes kittens, cats with feline leukemia virus or feline immunodeficiency virus , or cats on immunosuppressive drugs such as cyclosporine are at increased risk. Cats become infected with toxoplasmosis by eating raw meat or an infected intermediate host (commonly rodents) where the organism is encysted in the muscle tissues. Most cats with toxoplasmosis never have any symptoms of illness. However, a few cats may become very ill with a variety of possible symptoms depending on where the organism is replicating (the central nervous system, liver, lungs etc.).
The antibiotic clindamycin is used to clear the infection. It may be difficult to fully clear depending on how compromised the cat is and where the infection is located. Cats with lung and liver infections have a more guarded prognosis. If improvement is not noted 2-3 days after starting the antibiotic, the prognosis is even more grave.
Parasitic causes of feline pneumonia
Parasitic causes of pneumonia in cats are typically from the lungworm Aelurostrongylus or occasionally from migrating roundworms.
Parasitic causes of pneumonia are more commonly found in kittens. Lungworms can cause more serious symptoms in kittens and should always be considered in kittens with respiratory distress. Free roaming young and adult cats are more likely to be infected with lungworms. Hunting cats are most at risk because the larvae for lungworm can be found in small rodents and some frogs, lizards, snakes and birds. When a cat ingests one of these intermediate hosts they can be infected with lungworm. Cats can also spread lungworm by fecal oral contact with infected cat feces.
Most cats have no symptoms from lungworm infections. In some cats (mostly kittens) it can cause weight loss, decreased appetite, trouble breathing and coughing. The diagnosis of lungworm is most commonly determined with a special fecal test called a Baermann fecal exam in order to find evidence of the larvae. Occasionally the larvae can be identified in the sputum from a cat or during a bronchoscopy procedure.
Roundworms are a common intestinal parasite that can be transmitted in utero, by nursing, and fecal oral contact with infected feces. Part of the lifecycle of the roundworm is passed through the lungs as a third stage larvae. If there is an unusually heavy burden of infection, it can cause serious pneumonia. Deworming procedures for kittens and puppies always involve deworming for roundworms.
Aspiration pneumonia in cats
A non-infectious cause of bacterial pneumonia is secondary to aspiration. Aspiration can be food material or stomach contents from regurgitation or vomiting. A common risk factor for aspiration pneumonia in cats is underlying gastrointestinal disease which can cause vomiting or regurgitation.
Feline aspiration pneumonia most commonly affects the right middle lung lobe (64% in one study), followed by the left cranial lung lobe. In 28 cases of cats with aspiration pneumonia, the underlying causes were identified as: vomiting, recent anesthesia, enteral feedings, underlying esophageal disease, a seizure disorder and laryngeal disease. Most cats survived to discharge after receiving supportive care with antibiotics and fluid therapy. The median hospitalization time was 3 days.
Interestingly cats that suffer from aspiration pneumonia have a much shorter duration and prevalence of cough ( less than 2 weeks) than cats with typical bacterial bronchopneumonia. Cats with bronchopneumonia have many months of coughing ( 6 to 9 months on average!) and a higher average resting respiratory rate of 43 bpm versus 26 bpm in cats with aspiration pneumonia.
The most frequently cultured bacteria in cats with bacterial bronchopneumonia is Mycoplasma. Bronchopneumonia should be suspected in cats with severe radiographic changes (many infiltrates ) and coughing.
Cats with a long standing cough (chronic cough)
Bronchopneumonia and inflammatory airway disease in cats (asthma) can both present as a long term chronic intermittent cough. It is thought that a cat’s generally sedentary lifestyle may obscure other clinical symptoms. Wheezing was actually reported more often by owners of cats diagnosed with bronchopneumonia than in cats with asthma.
Other respiratory emergencies in cats
The most common causes of respiratory emergencies in cats are: asthma, heart failure and pleural effusion (a condition where fluid builds up around the lungs). A diagnosis of pneumonia is very rare.
Interestingly,coughing is not a common feature noted in cats with heart failure, whereas coughing does occur with asthma and occasionally with pleural effusion. Cats that present to the emergency room with respiratory difficulties can sometimes pose a challenge to the veterinarian to identify the cause of their poor lung function. This happens because pneumonia and heart failure can look the same on a lung X-ray.
A common bedside test utilized to help distinguish if the respiratory problems is due to heart dysfunction or a primary lung disease is called an NTproBnp test. This measures a cardiac muscle enzyme. This enzyme rises with significant heart disease.
Home treatment for cats with pneumonia
Cats that have bacterial pneumonia that are well enough to be cared for at home with oral antibiotics will also benefit from a few things you can do for them at home.
Keeping your cat well hydrated during a bout of pneumonia is of paramount importance because the mucociliary apparatus which lines the airways in the lungs functions best when well hydrated. This system helps to remove bacteria and mucus from the airways via small fingerlike projections on the lining of the airways. A lot of cats don’t drink much water.
A few tricks to encourage water consumption is to provide running water via a cat water fountain. Another good idea is to add flavoring to their water by adding some tuna juice or clam juice to their water dish. Finally, I also recommend a unique hydration product marketed by Purina called Hydracare. This is an electrolyte gel packet that is flavored into a tasty gel. It can enormously boost a cat’s hydration compared to drinking water alone.
It is also important to encourage your cat to inhale steam by placing them in an enclosed bathroom while running a hot shower. You can also purchase a small saline nebulizer unit from your pharmacy.
If your cat does not have a robust appetite, you should try gently warming their food to increase its aroma. Offer a buffet of food options to keep your cat interested in eating.
Because you may not know how transmissible your cat’s infection is to any other cats in your home, you should separate your cats. Wash your hands before touching any other cats and always wash your sick kittie’s food and water bowls well.
Conclusion for Pneumonia in cats
Remember that most respiratory emergencies in cats are due to three main diseases: asthma, heart failure and pleural effusion. Pneumonia is not common! Coughing is not a typical symptom in cats with heart failure. Additional tests may need to be ordered by your veterinarian to determine the cause of trouble breathing in any cat.
These tests rely on imaging (chest x rays or point of care ultrasound of the lungs), blood testing to look for an elevation in a heart enzyme that rises with heart failure, and sometimes infectious disease testing and cultures of fluid from the lungs.
Overall the prognosis for most cases of feline pneumonia is good in an adult cat . Kittens or adult immunocompromised cats are at greater risk for more severe disease. These felines are at risk for pneumonia that is much more difficult to treat such as fungal infections, a severe herpes viral infection or a heavy worm burden in the lungs.