Pneumonia
Also known as: Bacterial pneumonia, Bacterial bronchopneumonia, Bronchopneumonia
Also known as: Bacterial pneumonia, Bacterial bronchopneumonia, Bronchopneumonia
In short
Pneumonia is a serious and potentially life-threatening lung infection in dogs and cats. Learn about the symptoms, causes, diagnostic tests, and why long-term antibiotic therapy is critical for recovery.

TL;DR. Pneumonia is a serious, potentially life-threatening lung infection in dogs and cats that impairs breathing and requires immediate veterinary care and long-term antibiotic therapy to resolve.

Pneumonia causes deep inflammation within the airways, peribronchial tissues, and alveoli of the lungs.
Pneumonia is a broad term used to describe inflammation of the lungs, but in dogs and cats, it most commonly refers to a deep, serious bacterial infection of the lower respiratory tract. To understand pneumonia, it helps to understand how the lungs are structured. When your pet breathes in, air travels down the trachea (windpipe) and branches into smaller tubes called bronchi. These bronchi branch further into tiny airways called bronchioles, which finally end in microscopic air sacs called alveoli. The alveoli are surrounded by tiny blood vessels; this is where oxygen enters the bloodstream and carbon dioxide is removed.
In a healthy pet, this system works seamlessly. However, when pneumonia develops, inflammation takes hold of these delicate tissues. The infection can involve the airways themselves, the surrounding supportive tissues (peribronchial tissues), and the alveoli. As the body fights the infection, the alveoli fill with inflammatory fluid, white blood cells, and cellular debris—a process veterinarians call consolidation. This fluid buildup acts as a barrier, severely impairing gas exchange and making it incredibly difficult for your pet to get enough oxygen, leading to respiratory distress.
Veterinarians use specific terms to describe how far the infection has spread. As noted in a leading veterinary internal medicine reference:
"The term pneumonia means inflammation of the lung, but the term is not specific for bacterial disease. Infection that clinically appears to be limited to the airways and peribronchial tissues is called bacterial bronchitis. If all three regions are involved, the disease is called either bacterial bronchopneumonia or bacterial pneumonia." — Textbook of Veterinary Internal Medicine
Bacterial pneumonia occurs when bacteria manage to bypass your pet's natural respiratory defenses (such as the nasal passages, the cough reflex, and microscopic hair-like structures called cilia that sweep debris out of the airways). The most common bacteria isolated from dogs and cats with pneumonia include Escherichia coli (E. coli), Klebsiella species, Pasteurella species, Pseudomonas species, Bordetella bronchiseptica, and Streptococcus species.
These bacteria can enter the lungs through three primary routes:
Several physical and environmental factors can significantly increase a pet's risk of developing pneumonia:
As detailed in a leading veterinary critical care reference:
"Cleft palate Congenital abnormality that may cause ingesta to enter nasal cavity with subsequent aspiration Crowded or unclean housing Persistence and concentration of infectious organisms in environment contributors to risk Forceful bottle feeding* Aspiration possible when care provider squeezes the nursing bottle during suckling or if hole in nipple is too " — Small Animal Critical Care Medicine
There are no documented breed predispositions for pneumonia in our clinical records; any dog or cat can develop this condition if exposed to the right risk factors.
The clinical signs of pneumonia can vary between dogs and cats. It is a common misconception that all pets with pneumonia will have a loud, hacking cough. While coughing is common in dogs, it is remarkably rare in cats, which can make diagnosing feline pneumonia more challenging for owners.

Cats with pneumonia rarely cough; instead, they often show subtle signs like rapid breathing or an extended neck.
Understanding the difference in how dogs and cats show these signs is critical. A leading veterinary critical care reference highlights this disparity:
"Most dogs with pneumonia (>90%) do have abnormally loud breath sounds, crackles, or wheezes on pulmonary auscultation6 ; however, these findings are nonspecific and do not allow differentiation from other causes of dyspnea (pulmonary edema, pulmonary hemorrhage). In contrast to dogs (47%),6 cats with infectious pneumonia rarely cough (8%). 3 Mucopurulent nasal discharge may or may not be presen" — Small Animal Critical Care Medicine
If your vet suspects pneumonia, they will perform a comprehensive diagnostic workup. Because respiratory distress can look similar regardless of the underlying cause (such as heart failure, asthma, or internal bleeding), precise testing is required to confirm pneumonia and tailor the treatment plan.

An endotracheal wash allows veterinarians to collect fluid directly from the lower airways for culture and cytology.
As emphasized in veterinary medicine:
"Confirmation of bacterial lung infection requires demonstration of inflammation and infection in the lower respiratory tract. This information usually is obtained via transtracheal wash (TTW) or endotracheal wash (ETW), both of which can yield specimens for cytologic evaluation and bacterial or fungal culture and susceptibility testing." — Small Animal Critical Care Medicine
Treating pneumonia requires an aggressive, multi-faceted approach. Because pneumonia can quickly become life-threatening, treatment is often started immediately, even before the results of bacterial cultures are returned.
Initial treatment is typically empirical, meaning the vet selects broad-spectrum antibiotics known to target the most common respiratory bacteria.
A leading internal medicine reference outlines this initial approach:
"Dogs or cats with uncomplicated community-acquired pneumonia should receive doxycycline or a fluoroquinolone while completing the diagnostic workup. Chloramphenicol can be used as well for large breed dogs if fluoroquinolones are cost prohibitive. Common bacteria associated with pneumonia in dogs include E. coli, Klebsiella spp. , Pasteurella spp. , Pseudomonas spp. , B. bronchiseptica, Streptococ" — Textbook of Veterinary Internal Medicine
For severe, hospitalized, or resistant cases, your vet may utilize other classes of antibiotics, often in combination:
Antibiotics alone are often not enough. Supportive therapies are vital to help your pet breathe and clear the infection:
The prognosis for pets with pneumonia is highly variable and depends heavily on the severity of the disease, the underlying cause, and how quickly veterinary treatment is initiated. Many pets with uncomplicated, community-acquired pneumonia make a full recovery with prompt care. However, cases involving severe aspiration, resistant bacterial strains, or underlying anatomical issues (like cleft palates) carry a much more guarded prognosis.
A critical component of a successful outcome is the duration of treatment. Pneumonia cannot be cured with a standard 7-to-10-day course of antibiotics. It requires long-term antibiotic therapy lasting at least 4 weeks, or 1 to 2 weeks beyond the complete resolution of clinical signs on chest X-rays.
Your vet will schedule regular recheck appointments, which must include follow-up chest X-rays. It is vital to continue antibiotic therapy until the X-rays show that the lungs are completely clear, even if your pet seems entirely back to normal. Stopping antibiotics too early is a common cause of severe, treatment-resistant relapses.
While not every case of pneumonia can be prevented, you can significantly reduce your pet's risk by taking several proactive steps:
Pneumonia is a progressive disease that can rapidly escalate into a life-threatening crisis. You should contact your veterinarian immediately if your pet develops a persistent cough, becomes lethargic, or loses their appetite.
Seek immediate emergency veterinary care if you observe any of the following red flags:
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
Pneumonia is a serious and potentially life-threatening lung infection in dogs and cats. Learn about the symptoms, causes, diagnostic tests, and why long-term antibiotic therapy is critical for recovery.
Abnormally loud breath sounds, crackles, or wheezes、Cough、Inappetence、Increased respiratory effort、Lethargy、Tachypnea、Weight loss、Depression
Arterial blood gas evaluation、Complete Blood Count (CBC)、Endotracheal wash (ETW)、Pulse oximetry、Three-view thoracic radiography、Transcutaneous fine-needle aspiration of lung tissue
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app