Kennel cough results from inflammation of the trachea. It is a mild, self-limiting disease but may progress to bronchopneumonia in puppies or to chronic bronchitis in debilitated adult or aged dogs. The illness spreads rapidly among susceptible dogs housed in close confinement (eg, veterinary hospitals, doggy daycare, boarding facilities, kennels). Dogs of all ages can be affected, with puppies more prone to severe disease.
Etiology of Kennel Cough
Kennel cough has multiple etiologies, including Bordetella bronchiseptica, canine parainfluenza virus (CPIV), canine adenovirus 2 (CAV-2), canine influenza, and less likely canine distemper virus. Canine reoviruses (types 1, 2, and 3), canine herpesvirus, and canine adenovirus 1 (CAV-1) are of questionable significance in this syndrome. Bordetella bronchiseptica may act as a primary pathogen, especially in dogs < 6 months old; however, it and other bacteria (usually gram-negative organisms such as Pseudomonas sp, Escherichia coli, and Klebsiella pneumoniae) may cause secondary infections after viral injury to the respiratory tract. Co-infections with B bronchiseptica, CPIV, and CAV-2 are most common. The role of Mycoplasma sp has not been clearly established. Stress and extremes of ventilation, temperature, and humidity apparently increase susceptibility to, and severity of, the disease.
Clinical Findings of Kennel Cough
The prominent clinical sign of kennel cough is a cough that sounds like a "goose honk" that may be followed by retching and gagging. The cough is easily induced by gentle palpation of the larynx or trachea. Development of more severe signs, including fever, purulent nasal discharge, depression, anorexia, and a productive cough, is indicative of bronchopneumonia. Stress, particularly due to adverse environmental conditions and improper nutrition, may contribute to a relapse during convalescence.
Diagnosis of Kennel Cough
History and clinical signs
Radiography
Kennel cough should be suspected whenever the characteristic cough suddenly develops 5–10 days after exposure to other susceptible or affected dogs. Severity usually diminishes during the first 5 days, but the disease persists for 10–20 days. Tracheal trauma secondary to intubation may produce a similar but generally less severe syndrome. Thoracic radiographs are essential to determine the severity of disease and to exclude other causes of cough. Thoracic radiographs are often normal in dogs with a cough only. Dogs may have evidence of alveolar disease if the disease has progressed to pneumonia. Nasopharyngeal or tracheal swabs may be taken for PCR testing to evaluate for the cause of the clinical signs.
Treatment of Kennel Cough
Supportive therapy
Antimicrobial therapy only if indicated by culture and sensitivity
Dogs with a cough only often do not require hospitalization. If a dog requires hospitalization, it should be housed in isolation from other animals in the hospital. The disease is often self-limiting, and antibiotics are usually not needed unless there is evidence of pneumonia. The antibiotics recommended include amoxicillin/clavulanic acid 12–25 mg/kg, PO, every 12 hours; trimethoprim-sulfa drugs 15–30 mg/kg, PO, every 12 hours (schirmer tear test should be performed before starting medications); enrofloxacin 10 mg/kg, PO, every 24 hours; and doxycycline or minocycline 5–10 mg/kg, PO, every 12 hours for 7–14 days. When needed, the antibiotic should be selected by culture and sensitivity tests of specimens collected by tracheal wash or bronchoscopy. Antitussives are contraindicated in patients with pneumonia. If the cough is persistent, hydrocodone at 0.22 mg/kg, PO, every 6–12 hours or butorphanol at 0.5 mg/kg, PO, every 6–12 hours, or both as needed, can be used.
Prevention of Kennel Cough
Dogs should be immunized with modified-live virus vaccines against distemper, parainfluenza, and CAV-2, which also provides protection against CAV-1. Commercial products frequently combine these agents and may include modified-live parvovirus and leptospiral antigens. An initial vaccination should be given at 6–8 weeks and repeated twice at 3- to 4-week intervals until the dog is 14–16 weeks old. Revaccination should be performed annually. When the risk of B bronchiseptica infection is significant, a live, avirulent, intranasal vaccine or parenteral products containing subunit bacterial extracts should be used. A combination of an avirulent B bronchiseptica and a modified-live parainfluenza vaccine is available for intranasal use. One inoculation is administered to puppies >3 weeks old.
Key Points on Infectious Tracheobronchitis of Dogs
Dogs with kennel cough should be housed separately from other dogs. Personal protective equipment should be used and good hygiene practiced (hands washed before and after working with an infected dog).
All dogs are susceptible, with puppies being at higher risk of infection.
