Allergic Pneumonitis in Cats

Allergic pneumonitis in cats is the term veterinarians use to describe an acute or chronic reaction of allergenic nature, isolated to the small airways and lungs of a feline. Allergic pneumonitis is characterized by an overreaction of the lungs caused by a parasitic inhabitance or the presence of an underlying irritant. The allergic reaction inside the lungs and respiratory system causes the feline to cough, paired with the inability to conduct regular breathing habits. Therefore, many cats affected by this pneumonitis condition often require oxygen therapy and immediate veterinary attention, as lack of oxygen to the body is fatal. 

Allergic Pneumonitis often causes the total number of white blood cells, called eosinophils, to multiply, which your veterinarian may note on your cat’s blood work.  The most common symptom reported by cat owners in the case of allergic pneumonitis is a chronic cough. A cat may develop a mild or severe cough that may be described as a dry (no secretions), or wet (presence of saliva or mucus) cough. The feline may occasionally cough up bits of blood and develop a blue coloration to her mucous membranes (gums and tongue). Additional symptoms of allergic pneumonitis in cats that a pet owner may notice include:  

• Exercise intolerance
• Wheezing 
• Rapid breath 
• Weight loss 
• Labored breathing 

Depending on the condition of the alveoli (structure within the lungs) or respiratory airways, the degree of coughing and breathing difficulties vary from one cat to another. 

Although allergic pneumonitis is rarely pinpointed to an exact underlying cause, this feline condition is associated with secondary factors. Due to the fact that allergic pneumonitis causes a high level of eosinophils (white blood cells) in a cat’s blood, a condition known as pulmonary infiltration with eosinophilia is commonly associated with this allergic reaction. Pulmonary infiltration with eosinophilia, or PIE Syndrome, is caused by viruses, fungal infections, chronic bacterial infections, external antigens (outside allergens), parasites, and unknown factors. Heartworm disease is also believed to be a contributing cause, as the internal parasite migrates from the intestine to the heart and lungs. 

Your veterinarian will base his or her diagnosis of allergic pneumonitis on laboratory exams, chest x-rays, clinical signs, and your cat’s medical history. The veterinarian will ask you simple questions about your cat’s behavior over the past few days and ask for an estimate on how long you believe the symptoms have been occurring. After completing a thorough physical examination of your cat, the veterinarian will proceed to conduct the following diagnostic exams: 

• Heartworm test: a blood test used to diagnose the presence of the internal parasite. The test only requires a small amount of blood and results can be determined within minutes. 
• Blood Work: laboratory blood work test can show an elevated level of eosinophils, indicating the feline is suffering from an infection or internal inflammation. 
• Fecal analysis test: a fecal exam can indicate the presence of internal parasites, as parasitic eggs are often shed in the feces of an infected feline. 
• Radiographs (x-rays): an x-ray of the feline’s chest will indicate inflammation, lung parasites, and other abnormalities within the lower respiratory system. 

Felines presented to the clinic with allergic pneumonitis often have severe shortness of breath, therefore, the vet may begin treatment with oxygen therapy for stabilization purposes. Whether your cat’s allergic pneumonitis condition is due to an external antigen, internal parasite or is even unknown, the main treatment for this lung condition is corticosteroid therapy. If your cat’s allergic pneumonitis is idiopathic (unknown underlying cause), a corticosteroid may be the only treatment prescribed until an underlying cause can be found. However, if an underlying cause can be found, the veterinarian will want to eliminate the offending agent from the feline’s body. Eliminating the offending agent may entail the use of an anti-parasitic drug, antibacterial, or antifungal agent. The veterinarian may also prescribe an anti-inflammatory drug, beta2-agonist medication, or bronchodilator to open the feline’s airways, and reverse the body’s inflammatory response to the infection. 

The recovery time for allergic pneumonitis in cats depends on the underlying cause of the condition and whether or not a contributing factor was pinpointed. Felines with idiopathic (unknown) allergic pneumonitis often require long-term corticosteroid therapy until symptoms resolve, or a cause is found. Other felines recover after the underlying irritant has been removed, such as the presence of bacteria, fungus or internal parasites. Felines with allergic pneumonitis caused by a bacterial or fungal infection have a very positive prognosis, whereas a parasitic infection poses a lesser prognosis. Pet owners can better their feline’s prognosis by following veterinary instruction and completing the total course of prescribed medication.