Introduction
The classic signs of upper respiratory tract (URT) infection in dogs include sneezing, coughing, nasal irritation (scratching, pawing, head/face/nose rubbing) and nasal and ocular (eye) discharge. Other common signs include low-grade fever, dyspnea (difficulty breathing), lethargy (tiredness) and loss of appetite, especially in progressively severe cases. The precise signs of clinical disease will depend upon its cause.
Symptoms of Upper Respiratory Tract Infection in Dogs
Bordetella bronchiseptica Infection
Upper respiratory tract infection caused by Bordetella bronchiseptica (commonly called “kennel cough”) generally presents with a deep, dry, hacking and nonproductive cough, without other signs of illness or discomfort. Sneezing, snorting, retching and gagging can also occur, with or without production of a pale, frothy foam from the mouth. Clinical signs often worsen with exercise or excitement. Symptoms normally develop 4 to 5 days after exposure to an infected dog, which usually happens in a high-dog-density boarding kennel, animal shelter, dog show or dog park situation, where dogs congregate in what can be less than ideal hygienic conditions.
Secondary Bacterial Infections
The clinical signs associated with URT infection 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. However, if secondary bacterial infections, particularly bronchopneumonia, occur in association with an upper respiratory tract infection, the illness can become quite severe. Dogs suffering from pneumonia generally have extreme dyspnea (difficulty breathing) and may have trouble rising or moving. They may refuse to participate in activities and may just “lie around.” They frequently lose their appetite and have a low-grade fever.
Canine Influenza Virus (CIV) Infection
Clinical signs of URT infection caused by the recently-identified canine influenza virus include coughing and a clear, thin nasal discharge that progressively becomes thick and green, usually due to secondary bacterial infection.
Canine Distemper Virus Infection
The canine distemper virus causes fever and ultimately often fatal disease that has respiratory, gastrointestinal and central nervous system manifestations. The disease is much more common in puppies than in adults. Respiratory signs mimic those of other viral and bacterial pathogens and include nasal and ocular (eye) discharge, fever, cough, lethargy and inappetance. Distemper can progress to multifocal central nervous system signs, including dyspnea (difficulty breathing), vision disturbances, vomiting, diarrhea, paralysis, hardening of the footpads and nose, muscle tremors, seizures and death.
Canine Parainfluenzavirus Infection (CPI) and Canine Adenovirus Type 2 (CAV-2) Infection
CPI damages the lining of the upper respiratory tract and primarily causes a dry cough and a clear, thin nasal discharge. CAV-2 also replicates in and damages the lining of the upper respiratory tract, mimicking “kennel cough.” These viruses can damage the respiratory epithelium so severely that affected dogs are highly likely to develop serious upper airway disease, including bronchopneumonia.
Parasites
The canine nasal mite, Pneumonyssoides caninum, can 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. These mites also commonly cause head shaking, pawing at the nose and reverse sneezing. Lung flukes (Paragonimus kellicotti) often cause no clinical signs at all. When they do, the most commonly seen sign is a chronic, deep cough that is unresponsive to antibiotics.
If you notice that your dog is exhibiting signs of upper respiratory tract infection, particularly if it has recently been boarded, to a dog show, to the dog park or otherwise exposed to a number of other dogs in close quarters, please make an appointment with your veterinarian as soon as possible.