Causes of Upper Respiratory Infection in Dogs
Dog Breeds
Upper respiratory infections in dogs are caused by viral and bacterial infections which affect the dog’s upper airways. In rare cases, upper respiratory infections in dogs can occur due to canine nasal mites and lung flukes.
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Introduction
The upper respiratory tract (URT) includes the nasal cavities, throat (larynx and pharynx) and upper part of the bronchial tree. Infections of the URT are common in dogs and tend to be caused by a combination of pathogens, including viruses, bacteria and/or mycoplasma (which are a particular type of bacteria). In rare cases, upper respiratory tract infections can be associated with canine nasal mites or lung flukes.
Causes of Upper Respiratory Tract Infection in Dogs
The two most common causes of URT infection in dogs are bacterial and viral. These infectious pathogens are highly contagious, especially when dogs congregate in high-density areas such as pet stores, animal shelters, boarding facilities, dog parks or dog shows, and even more so when those areas are not kept clean. Immunocompromised dogs, puppies and unvaccinated dogs are at an increased risk for developing URT disease.
Bacteria and Viruses
Bordetella bronchiseptica is the most common primary bacterial pathogen causing canine URT infection (it causes infectious tracheobronchitis, commonly called “kennel cough”). The signs associated with URT infection caused by Bordetella bronchiseptica are indistinguishable from the early signs caused by secondary bacterial pathogens, including Pseudomonas, Escherichia coli, Klebsiella, Pasteurella, Streptococcus, Mycoplasma and several other bacterial species.
Viral causes of canine upper respiratory tract infection in dogs include the canine distemper virus, canine adenovirus type 1 or 2 (CAV-1 causes infectious canine hepatitis and CAV-2 is a cause of kennel cough), canine parainfluenzavirus (CPI), canine influenza virus (CIV), canine reovirus type 1, 2 or 3 and canine herpes virus. CAV-2 and the canine parainfluenzavirus can damage the respiratory epithelium so severely that affected dogs are highly likely to develop serious upper airway disease.
Parasites
The canine nasal mite, Pneumonyssoides caninum, is an arthropod found in the nasal cavities and sinuses of dogs. When present, these mites cause sneezing, chronic nasal discharge (runny nose), coughing, inflammation and swelling of the nasal mucosa and epistaxis (nose bleeds), and can predispose infected dogs to secondary bacterial infections of the upper respiratory tract. They are transmitted between dogs based on direct contact with an infected animal. Fortunately, these nasal mites are uncommon in North American dogs.
Lung flukes (Paragonimus kellicotti) are trematode parasites that live within pulmonary cysts in the lungs of dogs, cats and other mammals, including people. There is no age, gender or breed predisposition to infection by lung flukes. For any mammal to become infected, it must somehow ingest part of an infected crayfish at some point in time (this is part of the life cycle of this parasite). Lung fluke infection often causes no visible clinical signs. The most common sign if any is seen is chronic coughing that does not respond to antibiotic therapy.
Which Dogs are at Risk?
Upper respiratory tract infections tend to occur in dogs with compromised immune systems, in puppies with immature immune systems and in adult dogs that are not up-to-date on their vaccinations. Dogs that are not vaccinated against Bordetella bronchiseptica are at a higher risk of developing these infections, particularly in high-dog-density environments.
Preventing Upper Respiratory Infections
Overview and Facts