Canine Infectious Tracheobronchitis

Also known as: Kennel Cough — Canine respiratory disease complex — Infectious Canine Tracheobronchitis — Infectious Canine tracheitis

Description

A highly contagious acute respiratory disease spread by close contact causing laryngitis, tracheitis, bronchitis and in some cases a rhinitis.

Multiple agents are implicated in the disease including Canine Adenovirus 1,Canine Adenovirus 2,Canine Herpes virus, Canine Parainfluenza - 2, Canine Distemper Virus, Mycoplasma species and Bordetella bronchoseptica. Most cases involve a primary viral infection and sometimes with secondary bacterial involvement. B.bronchoseptica adheres to ciliated epithelial cells in the trachea where it proliferates and releases toxins causing epithelial necrosis and prevents ciliary clearance. Mortality rates are very low and it is a common disease in dogs that are housed in groups.

Signalment

Affects dogs of all ages. Puppies and immunocompromised dogs are often worst affected.

History and Clinical Signs

Often a history of exposure to other dogs at either rehoming centers, bording kennels, or in a hospital etc. Direct contact or aerosol spread are the most common routes of infection. Clinical signs develop 3-5 days after exposure. Signs are often mild and self limiting. Affected dogs usually have a dry hacking cough which is likely to be exacerbated on exercise or excitement. Sometimes sneezing, serous nasal discharge and lymphadenopathy are present. The clinical signs typically persist from 2-3 days to 2-3 weeks.

Systemic signs are likely to indicate the development of bronchopneumonia, signs include pyrexia, inappetance and depression. Systemic disease is more likely to occur in young or immunocompromised animals. This condition is usually a result of secondary infection with Pasturella species and Streptococci bacteria. If widespread systemic signs are present infection with canine distemper virus should be suspected.

Diagnosis is most often made on history and physical exam ruling out other causes of the cough.

Laboratory Tests

Haematology and Biochemistry will help to look for an underlying cause of disease in immunocomprommised animals. Additionally they may show signs of infection including a Neutrophilia sometimes with a left shift.

Radiography

Thoracic radiography and ultrasound are often unremarkable however may help to rule out other causes of the cough.

Endoscopy

Only considered when it is necessary to rule out a number of alternative diagnoses. Will enable collection of samples from the respiratory tract. Often no specific findings however, tracheal cytology may reveal increased numbers of neutrophils and bacteria. Samples for bacteriology from the upper airways may be deceptive as they are likely to harbour commensal organisms. Ideally samples should be collected from the lower airways by a transbronchial wash.

Treatment

Uncomplicated cases are often self limiting and will resolve with a regime of strict rest for 7 days until coughing subsides. Antibiotic treatment is indicated if the animal is showing signs of systemic illness or if there is bronchopneumonia present. Where culture and sensitivity has been undertaken an appropriate antibiotic should be chosen on these results otherwise doxycycline, erythromycin, chloramphenicol or a potentiated sulphonamide are good choices.

Antitussives and bronchodilators may be used to alleviate severe coughing. Nebulization can also be useful to help loosen bronchial and tracheal secretions.

In patients with severe disease further supportive care including fluids and enteral feeding will be required. Anti-inflammatories may help relieve some of the clinical signs however there use is contra-indicated in immunocompromised animals.

Control

Vaccines can prevent or reduce the severity of disease caused by B. bronchiseptica, parainfluenza virus and adenovirus. Vaccinated animals can still contract the disease as multiple agents are implicated. Vaccines are available to be given systemically or intranasally. Intranasal vaccination provides mucosal IgA immunity and the presence of maternal antibodies do not affect actions of the vaccine.. It is important to practice good husbandry in areas where groups of dogs mix e.g boarding kennels . Ideally all animals should be vaccinated, any infected animals should be isolated to minimise the spread to unaffected animals and all fomites that have come into contact with an affected animal must be disinfected. Areas should be kept well ventilated and ideally animals should be kept in low population densities.

Prognosis

Good, generally self limiting.

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References

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2) W.B. Saunders Company

Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial