Pneumonia in Cats
Pneumonia — infection and inflammation of the lung tissue itself — is less frequently diagnosed in cats than in dogs, but when it does occur it should always be taken seriously. Cats are adept at hiding illness, which means that by the time obvious signs of breathing difficulty appear, the infection may already be well established. Knowing what to look for and acting promptly gives your cat the best chance of a full recovery.
What Causes Pneumonia in Cats?
Feline pneumonia can be triggered by several different types of infectious agents, and sometimes by a combination of more than one.
Viral Causes
Viral respiratory infections are extremely common in cats and frequently provide the initial foothold that allows bacterial pneumonia to develop. The two most important viruses are:
- Feline herpesvirus (FHV-1) — also known as feline viral rhinotracheitis, this virus causes upper respiratory infection that can spread downward into the lungs, especially in young, elderly, or immunocompromised cats
- Feline calicivirus (FCV) — another common respiratory virus that in rare cases can cause severe pneumonia, particularly with highly virulent strains
Both of these viruses are among the pathogens targeted by the standard feline vaccination protocol, which is one reason vaccination is so important even for largely indoor cats.
Bacterial Causes
Bacterial pneumonia in cats often occurs secondary to viral infection, but can also arise on its own. Common bacterial agents include Bordetella bronchiseptica, Pasteurella multocida, and Mycoplasma species. Aspiration of food, liquid, or vomit into the lungs — less common in cats than in dogs — can also introduce bacteria and trigger severe inflammation.
Other Causes
Fungal pneumonia, caused by organisms such as Cryptococcus or Aspergillus, can occur in cats with weakened immune systems. These cases are rarer and require a very different treatment approach. Cats with feline immunodeficiency virus (FIV) or feline leukaemia virus (FeLV) are at heightened risk of opportunistic infections affecting the lungs.
Recognising the Symptoms
The early signs of pneumonia in cats can be subtle, particularly in stoic individuals. Look out for:
- Persistent or worsening cough — not all cats with pneumonia cough, but when they do it is usually productive and sounds harsh
- Rapid breathing (more than 40 breaths per minute at rest) or visible effort with each breath
- Lethargy — sleeping more, less interested in play, or reluctant to jump onto usual perches
- Reduced appetite or complete refusal to eat
- Fever — your cat may feel warm to the touch around the ears and paws
- Nasal discharge, sneezing, or weeping eyes, especially if a viral upper respiratory infection is involved
- Open-mouth breathing — this is always abnormal in a cat that is not severely overheated and requires urgent veterinary attention
- Blue or pale grey gums, indicating a critical lack of oxygen
Cats rarely pant or breathe with their mouths open unless they are in significant respiratory distress. If you observe this, treat it as an emergency.
Diagnosis
Veterinary Examination
Your vet will listen to your cat's chest carefully. In pneumonia, the normal breath sounds are often replaced by crackles, wheezes, or areas of dullness where fluid or consolidation has accumulated. The pattern of abnormal sounds helps to localise where in the lungs the disease is most active.
Chest X-rays
Radiographs are essential for confirming pneumonia and assessing its severity. Areas of increased density (consolidation) within the lung tissue are characteristic. X-rays also help rule out other serious conditions such as pleural effusion (fluid around the lungs), heart disease, or a lung tumour that might cause similar symptoms.
Blood Tests
A complete blood count and biochemistry panel help assess the severity of infection, identify any organ involvement, and check that your cat is well enough to tolerate anaesthesia if further diagnostics or procedures are needed. An elevated white cell count is common in bacterial pneumonia.
Cultures and Swabs
Where possible, identifying the causative organism allows treatment to be tailored precisely. Nasal or throat swabs, or samples collected by tracheal wash, can be sent for bacterial culture and sensitivity testing, indicating which antibiotics will be most effective.
Treatment
Antibiotics
When a bacterial cause is confirmed or suspected, antibiotics form the core of treatment. The choice of antibiotic may be adjusted once culture results return. Courses are typically long — often three to six weeks — and the full course must always be completed to prevent relapse and reduce the risk of antibiotic resistance.
Antiviral and Supportive Medications
There are limited antiviral options for cats, but famciclovir can be used in cases linked to feline herpesvirus. Lysine supplementation has historically been recommended but evidence for its benefit is now considered weak. Supportive care — fluids, nutritional support, and anti-nausea medication if needed — is often just as important as targeted treatment.
Oxygen Therapy
Cats with significant breathing difficulty may need supplementary oxygen in hospital, delivered via an oxygen cage or a flow-by mask. This provides immediate relief while the underlying infection is addressed.
Nursing Care at Home
Once your cat is stable enough to return home, attentive nursing plays a crucial role in recovery:
- Keep your cat indoors, warm, and away from draughts
- Offer small, frequent meals of strong-smelling food — respiratory illness often reduces a cat's sense of smell, making food less appealing
- Gently wipe nasal discharge away with a damp cotton wool pad to keep the nostrils clear and make breathing easier
- Use a humidifier in the room where your cat rests to help loosen secretions
- Minimise stress — keep other pets away if your cat seems overwhelmed, and keep the environment calm and quiet
- Administer all medications exactly as prescribed and complete the full course
Prevention
The most effective preventive measure against viral pneumonia is keeping your cat's vaccinations up to date. The core feline vaccination covers herpesvirus and calicivirus, the two viruses most commonly involved in feline respiratory disease. Even if your cat lives entirely indoors, these vaccinations are recommended, as the viruses can be carried in on clothing or via contact with other cats.
Good dental care is also worth mentioning — dental disease and periodontal bacteria have been linked to aspiration pneumonia in some cats, particularly those with difficulty swallowing. Regular dental check-ups and appropriate dental hygiene at home contribute to your cat's overall respiratory health.
Any cat showing signs of respiratory illness — particularly those already known to carry herpesvirus or calicivirus — should be seen promptly by a vet before a mild upper respiratory infection has the chance to progress to something more serious.