Symptoms of Upper Respiratory Tract Infection
The classic signs of canine upper respiratory tract (URT) infection are very similar to the symptoms of the common cold in people. The symptoms of clinical disease in domestic dogs will depend upon the underlying cause of the condition.
Dogs with URT infections typically develop one or more of the following symptoms:
- Retching; gagging
- Coughing (deep, dry and hacking, or moist and productive)
- Production of pale, frothy foam from the mouth
- Nasal irritation (evidenced by scratching, pawing, head/face/nose rubbing and head-shaking)
- Nasal discharge
- Ocular (eye) discharge
- Fever (low-grade)
- Difficulty breathing (dyspnea)
- Labored breathing
- Lethargy; tiredness
- Loss of appetite (inappetence; anorexia)
- Weight loss
- Exercise intolerance
Dogs with an URT infection caused by Bordetella bronchiseptica (so-called “kennel cough”) generally have a deep, dry, hacking and nonproductive cough, without other signs of illness or discomfort. Clinical signs of kennel cough can worsen with exercise or excitement. Symptoms normally develop 4 or 5 days after exposure to an infected dog, which usually happens in areas where dogs congregate in what can be less-than-ideal hygienic conditions.
The signs associated with URT infection caused by Bordetella bronchiseptica are indistinguishable from the early signs of infection caused by secondary bacterial pathogens, such as Pseudomonas, Escherichia coli, Klebsiella, Pasteurella, Streptococcus, Mycoplasma and several other microorganisms. Secondary bacterial infections often progress to bronchopneumonia, which can become very severe. Dogs with pneumonia generally have extreme difficulty breathing (dyspnea) and may have trouble rising or moving. They frequently refuse to participate in normal activities, develop a low-grade fever and lose their appetite. Dogs with pneumonia should be taken to a veterinarian promptly.
The symptoms of URT infection caused by the canine influenza virus are similar to those caused by other organisms. In addition to coughing, dogs infected with canine influenza virus typically develop a clear, watery nasal discharge that progressively thickens and becomes yellowish-green due to secondary bacterial infection. The canine distemper virus causes respiratory, gastrointestinal and central nervous system symptoms, together with a high fever. Distemper can lead to generalized central nervous system signs, including vision disturbances, vomiting, diarrhea, paralysis, hardening of the footpads, muscle tremors, spasms, seizures and death. Distemper is much more common in puppies than in adults.
Canine parainfluenzavirus infection (CPI) and canine adenovirus Type 2 infection (CAV-2) both damage the lining of the upper respiratory tract and cause a dry, raspy cough and a clear, thin nasal discharge, mimicking “kennel cough.” These viruses can damage the respiratory lining so severely that affected dogs are especially prone to developing serious secondary upper airway disease, including bronchopneumonia.
The canine nasal mite, Pneumonyssoides caninum, causes sneezing, chronic nasal discharge (runny nose), coughing, inflammation, swelling of the nasal mucosa and epistaxis (nose bleeds). These mites also commonly cause head-shaking, pawing at the nose and reverse sneezing. They predispose infected dogs to secondary bacterial infections of the upper respiratory tract. Dogs with lung flukes (Paragonimus kellicotti) often have no symptoms at all. When they do, the most common sign is a deep, chronic cough that is unresponsive to antibiotic therapy.
Dogs at Increased Risk
Puppies, unvaccinated animals, elderly dogs and dogs with impaired immune systems have an increased risk of developing upper respiratory tract infections.