The 3 Types of Pneumonia That Affect Cats and Dogs

The 3 Types of Pneumonia That Affect Cats and Dogs


  • Cats and (more often) dogs can develop pneumonia of three different types: bacterial, fungal, and aspiration (inhalation)
  • Bacterial pneumonia is caused by a variety of pathogens; symptoms include cough, fever, and difficulty breathing
  • Fungal pneumonia describes a deep lung infection which can be caused by several different fungi; symptoms include loss of appetite, weight loss, fever, and coughing
  • Aspiration pneumonia, which is life-threatening, is the result of inhalation of a foreign substance; symptoms include difficulty breathing, difficulty swallowing, and coughing

Editor's Note: This article is a reprint. It was originally published June 03, 2021.

Just like humans, dogs and cats also develop pneumonia. There are three types that commonly affect pets: bacterial, fungal and aspiration pneumonia, and the following is a discussion of each type.

Bacterial Pneumonia

The inflammation seen in bacterial pneumonia is characterized by cells and fluid that accumulate in the lungs, airways, and alveoli (tiny balloon-shaped structures in the respiratory system). The cause of the infection and inflammation is pathogenic bacteria. Bacterial pneumonia is more often seen in dogs than cats, especially sporting dogs, hounds, and large mixed-breed dogs.

No single type of pathogen is responsible for bacterial pneumonia, though there are some organisms more frequently seen than others in both dogs and cats. In dogs, Bordetella bronchiseptica (kennel cough) and Streptococcus zooepidemicus are usually the culprits. In cats, it’s Bordetella bronchiseptica, Pasteurella, and Moraxella that are more commonly cultured. But other organisms, including anaerobic bacteria, can also cause infection.

Conditions that seem to predispose some pets to bacterial pneumonia include a preexisting viral infection, problems swallowing, regurgitation, and metabolic disorders. Symptoms of bacterial pneumonia include:

  • Cough
  • Lethargy
  • Fever
  • Nasal discharge
  • Breathing difficulties (including rapid breathing)
  • Dehydration
  • Loss of appetite; weight loss
  • Exercise intolerance

When your veterinarian listens to your pet’s lungs with a stethoscope, she may hear abnormal breathing sounds known as crackles (short, snapping sounds), as well as some whistling or even wheezing.

If she suspects bacterial pneumonia, she may perform a transtracheal wash to obtain material from the lining of the trachea for analysis, including cytology and a culture and sensitivity test. X-rays of the chest and lungs may also be ordered along with a blood test to check for systemic infection.

Antimicrobial therapy will be needed in confirmed cases of bacterial pneumonia. The proper medication can be selected from the results of the bacterial cultures. If there are other symptoms like loss of appetite, those will also need to be addressed. Pets in respiratory distress may need oxygen therapy. Intravenous (IV) fluids are also sometimes ordered to either treat or prevent dehydration.

While he recovers, your pet will need plenty of rest, but you’ll need to ensure he doesn’t lie in one position too long to prevent fluid buildup on one side of the lungs or the other. You should encourage him to change positions often while he’s resting. Exercise should be limited to physiotherapy and activities to help clear the lungs and airways.

During the recovery period, I recommend supportive therapies, including antioxidants, specifically vitamin C and N-acetylcysteine, as well as probiotics.

Many pets have a full recovery from bacterial pneumonia when treated promptly and appropriately. Most deaths from pneumonia are the result of secondary complications, including hypoxemia (severely low levels of oxygen in the blood) and sepsis, which occurs when a localized lung infection spreads throughout the body.

Fungal Pneumonia

Fungal pneumonia is a very different problem from the bacterial form of pneumonia. This lung infection is the result of a deep fungal infection, sometimes called a mycotic infection. The inflammation caused by this type of infection can develop in the interstitial tissues, the lymphatic vessels, or in the peribronchial tissues of the lungs.

Like bacterial pneumonia, fungal pneumonia is more commonly seen in dogs than cats. Some breeds are more susceptible than others, for example, the German Shepherd. Male dogs are two to four times more likely to acquire this type of pneumonia than female dogs.

There are several types of fungi that can cause lung fungal infections, including Blastomyces, Histoplasma, and Aspergillus. Exposure to infection-causing fungi can happen through contact with soil that’s rich in organic matter, bird droppings, or feces. The method of infection depends on the type of fungus. For example, some fungi enter the body through inhalation via the mouth, while others enter through the nasal cavity. Symptoms of fungal pneumonia include:

  • Loss of appetite
  • Coughing
  • Weight loss
  • Difficulty breathing
  • Fever
  • Eye problems
  • Runny eyes or runny nose
  • Lameness

Your veterinarian may also hear abnormal lung sounds during the physical exam, but oddly, often a fungal infection will first present as an eye or skin problem.

The only way to definitively diagnose fungal pneumonia is to analyze the fluid collected on a transtracheal wash. If there are skin lesions present, performing a fine needle aspirate, lumpectomy, or biopsy of an enlarged lymph node can also yield the diagnosis of fungal infection. Other tests your vet may want to run include a urinalysis, X-rays of the chest and lungs, a fungal PCR assay, and an abdominal ultrasound.

Sadly, many dogs and an even greater percentage of cats are unresponsive to fungal pneumonia medication. In addition, treatment is very expensive and can last for two to six months or sometimes longer. The exact treatment depends on the type of fungus that has caused the infection.

Because fungal pneumonia can develop from dogs sniffing around in the wrong place at the wrong time and inhaling a whopping dose of fungi from the environment, discouraging dogs from digging at organic debris can help reduce the risk of acquiring fungal infections.

Aspiration Pneumonia

Aspiration pneumonia, also called inhalation pneumonia, is characterized by inflamed and infected lungs caused by inhaling (aspirating) substances, including vomit, food, foreign bodies, and regurgitated gastric acid. The severity of the condition depends on what material has been inhaled, what bacteria are present, and the distribution of the aspirated material into the lungs.

Like the other two forms of pneumonia discussed above, aspiration pneumonia is also more common in dogs than kitties. Newborn puppies are at higher risk, especially if they’re bottle-fed or have a cleft palate. Dogs who must be force-fed are also at a higher risk.

Aspiration pneumonia can result from disorders that adversely affect an animal’s respiratory system or increase the risk of aspiration, including any disease of the pharynx or larynx (which is the back of the throat), esophagus, stomach, or intestines.

These diseases can include laryngeal paralysis, gastroesophageal reflux (also called GERD), megaesophagus, tumors, paralysis of the complex swallowing mechanism, esophagitis (a fancy name for inflammation of the esophagus), pyloric outlet absorption (i.e., the stomach doesn’t empty properly), or trauma.

It’s not the act of vomiting that directly causes aspiration pneumonia. It’s the bringing up of contents from the stomach that are then inhaled. Inhalation of anything regurgitated can cause problems.

Induction of general anesthesia is also a trigger for this type of pneumonia. Normally, the placement of a tracheal tube prevents aspiration pneumonia. But sometimes pets can reflux before or after the tube is in place. And sadly, some veterinarians perform surgery without tracheal tubes, which dramatically increases the risks.

Other triggers can be inhalation of smoke, mineral oil, kerosene, gasoline, or any other caustic substance. Disorders that cause a state of altered consciousness such as seizure disorders can also increase the likelihood. Chronic vomiting can also put a dog at a higher risk of developing aspiration pneumonia.

Believe it or not, a quite common cause of aspiration pneumonia is faulty administration of liquid medication either delivered by drench (a stomach tube is passed down the back of the throat), or by a dose syringe. Any liquid that’s given via syringe, whether medication or food, must not be given any faster than the animal can swallow to prevent the possibility of aspiration pneumonia. Symptoms of aspiration pneumonia include:

  • Difficulty breathing
  • Increased heart rate
  • Difficulty swallowing
  • Exercise intolerance
  • Coughing
  • Vomiting
  • Fever
  • Regurgitation
  • Runny nose
  • Loss of appetite
  • Rapid breathing
  • Lethargy

Diagnosis of aspiration pneumonia is made through a thorough physical examination by a veterinarian. Your vet will do abdominal palpation, chest X-rays, a complete blood count, as well as a complete chemistry profile. In addition, fluid may be removed from the lungs to check for the presence of bacteria through culture and sensitivity testing, as well as cytology.

Aspiration pneumonia is a life-threatening condition and may require several days or more in an intensive care setting. If possible, airway suctioning should be performed immediately following the inhalation of foreign matter. If the animal is in respiratory distress, oxygen will be given. If there’s dehydration or shock present, those symptoms will be treated with an IV drip.

Until a diagnosis is made, the pet should not be given anything orally, especially in acute cases of aspiration pneumonia. Rest will be required, often cage rest in a very quiet, stress-free environment, but it’s important that the dog or cat is supervised. A pet with aspiration pneumonia should not lay his side for more than about two hours at a time.

If recovery is slow, as in the case of paralysis of the esophagus, continued medical care may be needed for up to several weeks. Once the patient is stable, mild exercise can stimulate expectoration or coughing to help clear the airways. Any underlying cause for the aspiration should be identified and resolved, if possible.

Unfortunately, a pet who has suffered from a serious case aspiration pneumonia has a poor prognosis, even with treatment. So, it’s imperative to focus on preventing the problem from happening and seeing a veterinarian immediately if you feel your pet may have aspirated something.