When the dog’s lungs, as well as the small airways, react to allergens, the resulting inflammation causes allergic pneumonitis. Internal parasites or irritant foreign bodies are the usual reason for this overreaction by the lungs. Chronic cough and other symptoms of respiratory distress may be present. Elevated blood count of eosinophils, a type of white blood cells, is another indication. In dogs, the cause of allergy is often difficult to identify.
Allergic pneumonitis is often associated with PIE syndrome in dogs. It is agroup of symptoms characteristic ofpulmonary infiltration with eosinophilia, usually caused by chronic viral, fungal or bacterial infections or parasitic infestations. Certain foreign proteins also may cause it, but the reason is not always known.
Parasites living in the lungs, as well as intestinal parasites that travel to the lungs during certain stages of their life cycle can irritate the lungs and cause allergic pneumonitis. Sensitivity to the microfilariae, which is the pre-larval form of heartworms, results in an allergic condition called Canine heartworm pneumonitis. A more severe form of this allergy is termed Pulmonary nodular eosinophilic granulomatous syndrome.
Allergic pneumonitis in dogs is characterized by a mild but chronic cough, which may be either productive or dry. In some cases it may be severe, and the dog may even cough up blood. Other respiratory problems include shortness of breath, difficulty in breathing accompanied by wheezing or rapid breathing. The severity of the respiratory symptoms is directly related to extent of inflammation in the respiratory tract and inside the air sacs in the lungs. A bluish tinge to the mucous membranes when the dog is at rest is another indication of respiratory distress. The dog may lose weight and become exercise intolerant too.
The typical symptoms, as well as the medical history of the dog, may lead to diagnosis, but lab tests and x-ray may be necessary to confirm the condition and detect its cause. Abnormally high WBC count indicates microbial infections or inflammatory conditions. If signs of heartworm infection or lung disease due to parasites are detected in the x-ray, further testing may be necessary to identify the exact cause. The veterinarian may conduct a heartworm test and fecal analysis.
When the cause of allergy can be determined, removal of the allergen along with a course of steroid drugs may eliminate allergic pneumonitis. If the condition is the result of parasitic infestation of the lung or heartworm infection, eliminating the parasites and administering the corticosteroids at the same time will be the remedy. If the cause of the allergy is not identified, the symptoms can be controlled using corticosteroids, but long-term use may be necessary. If the airway is severely constricted, drugs that relax the airway, such as beta2– agonists or bronchodilators may have to be given. Oxygen supplementation may be necessary if the dog has extreme shortness of breath.