Dog Pneumonia

What is Dog Pneumonia?

Pneumonia is irritation and inflammation within the lungs that results in the buildup of fluid within the air sacs. This compromises the normal exchange of oxygen and carbon dioxide within the lungs, resulting in difficult breathing. Pneumonia can be caused by various reasons, including:

• Bacteria
• Viruses
• Fungal organisms
• Parasites
• Immune-mediated
• Inhalation of stomach contents, food, chemicals, fluids, foreign materials
• Inhalation of chemicals, smoke

Pneumonia ranges from mild symptoms that affect small parts of the lungs to complete respiratory distress and an inability to breathe normally. Many cases of pneumonia require veterinary intervention immediately and should be treated as an emergency. 

Symptoms of Dog Pneumonia

Pneumonia causes many symptoms, ranging from mild to severe.  Most common symptoms include:

• Cough
• Labored breathing
• Nasal discharge
• Wheezing
• Fever
• Lethargy
• Respiratory distress
• Blue gums, in severe cases

Causes of Dog Pneumonia

Pneumonia has many origins, and often a dog can have multiple types of pneumonia at once. This happens most often with secondary bacterial infections.

Aspiration Pneumonia

Aspiration pneumonia occurs when a dog breathes in substances like food or vomit. It is one of the more common types of pneumonia.

The inhaled food material physically blocks air spaces and sets off an inflammatory cascade within the lungs. Stomach acids can also directly damage lung cells. All these factors combined create a perfect environment for a secondary bacterial infection. Some animals are at a higher risk for developing aspiration pneumonia due to factors such as:

• Laryngeal impairment
• Under sedation or anesthesia
• Neurologic disorders
• Medically required force-feeding
• Being prone to vomiting or regurgitation
• Brachycephalic breeds (Pugs, Bulldogs, Boston Terriers, etc.)

Bacterial Pneumonia

Bacterial pneumonia is common in dogs. Bacteria typically enters the lungs through aspiration or inhalation, but rarely spreads throughout the bloodstream. Most healthy adult animals do not acquire primary bacterial pneumonia. Puppies, seniors and immunocompromised dogs are more susceptible to bacterial pneumonia. Typically, this type of pneumonia is a secondary condition, or works in conjunction of a bigger respiratory issue involving multiple bacteria and viruses. Common bacteria found in dogs with pneumonia include:

• Bordetella
• Mycoplasma
• Yersinia
• Streptococcus
• E. coli
• Klebsiella
• Pseudomonas
• Enterococcus
• Pasteurella
• Bacillus
• Fusobacterium

Many factors contribute to a dog acquiring bacterial pneumonia. Dogs may be at risk with the following conditions:

• Viral or fungal pneumonia
• Immunosuppression from drugs or other illnesses
• Cancer
• Prolonged surgery
• Airway obstruction or anatomic abnormalities
• Vomiting and subsequent aspiration
• Metabolic disorders
• Abnormal mentation, such as seizures
• Inhaled foreign bodies
• Damaged cells in the lungs secondary to smoke or chemical inhalation, and drowning
• Sepsis 

Viral Pneumonia

These infections can involve more than one virus and may also be present with bacterial organisms. They spread primarily through inhalation and are typically highly contagious to other dogs. Dogs in shelters, long-term boarding, daycare or dog parks may be at a higher risk for viral pneumonia. Common organisms include:

• Canine influenza
• Canine distemper
• Canine adenovirus-2
• Canine herpesvirus
• Canine parainfluenza virus

Fungal Pneumonia

Fungal pneumonia is more common in the South and Southwest regions of the country. Dogs acquire fungal infections by inhaling fungus from contaminated soil or plants. Pets near construction or new homes, may be at an even higher risk. Common fungal pathogens include:

• Blastomyces
• Histoplasma

Parasitic and Protozoal Pneumonia

Parasitic and protozoal pneumonia occurs when living parasites live and reproduce in a dog’s lungs. Dogs may acquire parasites through contaminated feces and, in the case of heartworm, through insect vectors like mosquitos. This type of pneumonia is uncommon in dogs and includes:

• Neospora
• Toxoplasma

Eosinophilic or Allergic Pneumonia

Eosinophilic pneumonia occurs when the dog’s immune system causes a type of white blood cell (eosinophils) to flood the lungs. Respiratory tract irritants like spores, pollen or insect antigens may trigger this immune response.

Inhalation Pneumonia

Inhalation pneumonia may occur because of breathing noxious fumes or gases, including chemicals and smoke. Toxic particles interfere with the body’s ability to process oxygen normally, while also affecting the normal mucus and clearance within the lungs. 

How Veterinarians Diagnose Dog Pneumonia

Veterinarians use many diagnostics tests to diagnose pneumonia. Typically, they will start with listening to the lungs with a stethoscope. Fluid in the chest may sound like crackles, wheezes and pops. Occasionally, the lungs are only quieter than normal. This symptom, combined with coughing or difficulty breathing, may lead a veterinarian to recommend additional diagnostic tests.

Radiograph

Veterinarians use radiographs, or X-rays of the chest to diagnose pneumonia, and a specialized 3-view X-ray to help determine its severity. Fluid and inflammation look much different from air on X-rays, with gray, patchy or a hazy pattern. Pneumonia can affect one lung lobe or multiple lobes. Lungs can even collapse as fluid replaces the entirety of the air sacs.

Blood Chemistry and Complete Blood Count (CBC)

The complete blood count, or CBC, may show signs of inflammation and infection. The blood chemistry may show signs of sepsis in severe cases, as well as predisposing factors or reasons for vomiting.

Pulse Oximetry and Blood-Gas Analysis

Veterinarians use pulse oximetry and blood gas analysis to determine if the patient is receiving sufficient oxygen, and to confirm the presence of respiratory dysfunction. This is also an integral part of the follow-up and treatment monitoring process. Pulse oximetry, a small infrared light, is a non-invasive test that reads how much oxygen is present in the capillaries. Blood-gas analysis requires a special catheter to collect blood to analyze for oxygen, carbon dioxide and pH, among other things.

Culture and Cytology

Dogs with pneumonia may undergo procedures such as transtracheal washes, bronchoalveolar lavage and a bronchoscopy to obtain fluid samples from within the lungs. These procedures require special instruments designed to explore the respiratory tract and obtain the purest sample. Veterinarians can evaluate the samples under a microscope and look for cells and pathogenic organisms. Once cultured, veterinarians identify specific bacterial pathogens and then prescribe the best antibiotic therapy.

Other Tests

Veterinarians can use advanced imaging, such as MRI or CT to fully assess the extent of pneumonia and other risk factors. They may use other tests for infectious agents and parasites, including PCR, serology, etc. Blood cultures are rarely used, as a local culture typically yields good results.

Treatment of Dog Pneumonia

Therapy depends on the type of pneumonia and underlying pathology, or other illnesses. The severity of the disease will also dictate the intensity of treatment. Mild cases of pneumonia can be managed on an outpatient basis with medications, rest and home care. Moderate to severe cases require hospitalization - often at emergency facilities - with 24/7 nursing care and special equipment.

Antibiotics

Veterinarians prescribe antibiotics to dogs with primary or secondary bacterial pneumonia. Most common antibiotics include Doxycycline, Fluoroquinolone and Amoxicillin-clavulanic Acid. Treatment length is typically long-term, sometimes more than a month. Frequent rechecks help determine how long the antibiotics must be taken.

Oxygen Therapy

For animals who cannot oxygenate sufficiently on room-air, they are placed on supplemental oxygen. This may be a nasal or face mask, but veterinarians most commonly utilize an oxygen cage. An oxygen cage is an enclosed environment where the oxygen can be manipulated from room air (20 percent oxygen) to 100 percent oxygen. This is typically the least stressful way to supply oxygen to dogs in respiratory distress, and indicates the dog’s level of illness.

Fluid Therapy

Dogs with pneumonia are typically dehydrated and require an intravenous catheter and fluid therapy to rehydrate. Dehydration impairs respiratory clearance and function, so this is especially important in cases of pneumonia.

Nebulization and Coupage

Nebulizers create a fine mist and allow a localized increase in humidity, like the moist environment of a bathroom when the shower is on. Most nebulizers use saline to increase hydration of the airway but can also add antibiotics. After a nebulization treatment, dogs with pneumonia may have coupage performed, which is a gentle yet firm tap around the chest. Together, nebulization and coupage help break apart and clear mucus and other cells trapped in the airways.

Ventilation

Severe cases of pneumonia require full sedation and a ventilator to breathe. This is typically done if a dog does not respond to initial oxygen therapy or is minimally unresponsive. This typically happens only in an intensive care unit.

Recovery and Management of Dog Pneumonia

X-rays are typically taken every two to five days during the acute phase, and then every one to two  weeks (as needed) until complete resolution. X-rays should be monitored for recurrence every few months after full resolution. A veterinarian will want to recheck an exam as well as bloodwork within the first two weeks after an episode of pneumonia.

Most veterinarians recommend the continuation of treatment for at least a week after resolution of clinical signs – both patient symptoms and X-ray evidence.

Veterinarians do not typically recommend cough suppressants for dogs recovering from pneumonia. Coughing is the body’s natural way to remove the infection and fluid within the airways.