Definition

A multifaceted disease whereby infectious disease and environment contribute to the genesis of cough and other respiratory signs in dogs.

Pathophysiology

Initiated by injury to the respiratory epithelium by viral infection followed by invasion of damaged tissue by bacterial,, mycoplasmal, or other virulent organisms, resulting in further damage and clinical signs.

Systems Affected

Respiratory-upper and lower airways can be involved. Multisystemic-cases that develop sepsis.

Genetics

None

Incidence/Prevalence

Most common in areas of high density with immunologically naïve or immunosuppressed patients (i.e., training homes, shelters, veterinary hospitals).

Geographic Distribution

Worldwide

Signalment

Signs

Causes

• Viral-canine distemper virus; CAV-2; CPiV; canine respiratory coronavirus, canine reovirus; canine herpesvirus-1; canine influenza virus (H3N8 or H3N2); canine bocavirus, canine hepacivirus; canine pneumovirus.
• Most viral pathogens (except CHV and CDV) primarily infect epithelial and lymphoid tissue of the upper and lower respiratory tract; in severe cases, cause desquamation of the epithelium and aggregation of inflammatory cells in the lungs leading to secondary bacterial colonization and infection; canine respiratory coronavirus infection leads to loss of cilia associated with the respiratory epithelium, increasing the severity and duration of secondary infections.
• Bacterial-Bordetella bronchiseptica, with no other respiratory pathogens, produces clinical signs indistinguishable from those of other bacterial causes; Streptococcus equi subsp zooepidemicus is associated with a particularly virulent course that can progress to death; Pseudomonas, Escherichia coli, Klebsiella, Pasteurella, Streptococcus, Mycoplasma, and other species equally likely.

Risk Factors

• Substandard hygienic conditions and overcrowding-encountered in some pet shops, shelters, research facilities, and boarding and training kennels.
• Coexisting subclinical airway disease-congenital anomalies; chronic bronchitis; bronchiectasis.

Differential Diagnosis

• In systemically well dogs-parasitic bronchitis, irritant tracheobronchitis, tracheal foreign body, airway collapse.
• In a dog with systemic signs-fungal pneumonia, primary or metastatic neoplasia, congestive heart failure, migrating foreign body.
• Provisional diagnosis of infectious tracheobronchitis is made in a dog with compelling clinical signs and a history of exposure to the implicated organisms.
• See chapter, Cough.

CBC/Biochemistry/Urinalysis

• Early, mild leukopenia (5,000–6,000 cells/dL)-can be detected; suggests viral cause.
• Neutrophilic leukocytosis with a toxic left shift-frequently found with severe pneumonia.

Other Laboratory Tests

Pulse oximetry and arterial blood gas analysis-can reveal hypoxemia in pneumonia.

Imaging

• Uncomplicated disease: radiographs-unremarkable; most useful for ruling out other differential diagnoses.
• Complicated disease: radiographs-interstitial and alveolar lung pattern with a cranioventral distribution typical of bacterial pneumonia; can see diffuse interstitial lung pattern typical of viral pneumonia; mixed lung pattern can be present.

Diagnostic Procedures

• In cases with severe disease-ideally perform bronchoalveolar lavage via bronchoscopy for cytology and microbial culture; tracheal wash sample acceptable but increased likelihood for upper airway contamination.
• Antimicrobial sensitivity pattern of cultured bacteria-identification aids markedly in providing an effective treatment plan.
• PCR can be used to detect virus in BAL fluid, though there are limited reports of sensitivity and specificity.

Pathologic Findings

• CPI-causes few to no clinical signs; lungs of infected dogs 6–10 days after exposure may contain petechial hemorrhages that are evenly distributed over the surfaces; detected by immunofluorescence in columnar epithelial cells of the bronchi and bronchioles 6–10 days after aerosol exposure.
• CAV-2-lesions confined to the respiratory system; large intranuclear inclusion bodies found in bronchial epithelial cells and alveolar septal cells; clinical signs tend to be mild and short-lasting; lesions persist for at least a month after infection.
• Canine influenza virus (H3N8)-fulminant disease characterized by secondary Mycoplasma infection and pulmonary hemorrhage.
• Canine respiratory coronavirus-characterized by marked inflammation of the trachea and nares with cilia loss in the former; detected by immunohistochemistry of the trachea or bronchioles.
• Streptococcus equi subsp zooepidemicus infection-acute, fibrinosuppurative pneumonia with large numbers of cocci found within the pulmonary parenchyma and, often, septic thomboemboli.
• Bordetellosis and severe bacterial infection-evidence of purulent bronchitis, tracheitis, and rhinitis with hyperemia and enlargement of the bronchial, mediastinal, and retropharyngeal lymph nodes; may see large numbers of Gram-positive or -negative organisms in the mucus of the tracheal and bronchial epithelium.

Appropriate Health Care

• Outpatient-strongly recommended for uncomplicated disease.
• Inpatient-strongly recommended for complicated disease and/or pneumonia.

Nursing Care

Fluid administration-indicated for complicated disease and/or pneumonia.

Activity

Enforced rest-14–21 days with uncomplicated disease; for at least the duration of radiographic evidence of pneumonia in severely affected dogs.

Diet

Good-quality commercial food

Client Education

• Isolate patient from other animals; infected dogs can transmit the agent(s) before onset of clinical signs and afterward until immunity develops.
• Dogs with uncomplicated disease should respond to treatment in 10–14 days.
• Once infection spreads in a kennel, it can be controlled by evacuation for 1–2 weeks and disinfection with commonly used chemicals, such as sodium hypochlorite (1:30 dilution), chlorhexidine, and benzalkonium.

Drug(s) Of Choice

• Amoxicillin/clavulanic acid (12.5–25 mg/kg PO q12h) or doxycycline (5 mg/kg PO q12h)-initial treatment of uncomplicated disease.
• Penicillin (ampicillin 10–20 mg/kg IV q6–8h or ticarcillin 40–50 mg/kg IV q6–8h) with aminoglycoside (gentamicin 2–4 mg/kg IV, IM, SC q6–8h or amikacin 6.5 mg/kg IV, IM, SC q8h) or fluoroquinolone (enrofloxacin 5–10 mg/kg PO, IM, IV q24h)-usually effective for severe disease.
• Antimicrobial therapy-continue for at least 10 days beyond radiographic resolution.
• B. bronchiseptica and other resistant species-some antimicrobials may not reach adequate therapeutic concentrations in the lumen of the lower respiratory tract, so oral or parenteral administration may have limited effectiveness; nebulization with gentamicin (3–5 mg/kg)can decrease bacterial numbers when administered daily for 3–5 days. Use in conjunction with systemic antibiotics in dogs with parenchymal disease.
• Butorphanol (0.55 mg/kg PO q8–12h) or hydrocodone bitartrate (0.22 mg/kg PO q6–8h)-effective suppression of dry, non-productive cough not associated with bacterial infection.
• Bronchodilators (e.g., terbutaline 0.625–5 mg/dog q8–12h)-may use to control bronchospasm and wheeze.

Contraindications

• Do not use cough suppressants in patients with pneumonia.
• Employ glucocorticoids only in cases with significant inflammatory disease refractory to conventional supportive care.

Precautions

None

Possible Interactions

Fluoroquinolones and theophylline derivatives-concurrent use causes high and possibly toxic plasma theophylline concentration. Dose reduce theophylline while concurrently administering fluoroquinolones.

Alternative Drug(s)

None

Patient Monitoring

• Uncomplicated disease-should respond to treatment in 10–14 days; if patient continues to cough 14 days or more after establishment of an adequate treatment plan, question the diagnosis of uncomplicated disease.
• Complicated disease-repeat thoracic radiography until at least 7 days beyond resolution of all clinical signs.

Prevention/Avoidance

Shedding of the causative agent(s) of infectious respiratory disease in airway secretions of dogs undoubtedly accounts for the persistence of this problem in kennels, animal shelters, boarding facilities, and veterinary hospitals.

Possible Complications

N/A

Expected Course and Prognosis

• Natural course of uncomplicated disease, if untreated-10–14 days; simple restriction of exercise and prevention of excitement shortens the course.
• Typical course of severe disease-2–6 weeks; patients that die often developed severe pneumonia that affected multiple lung lobes and multiple organ dysfunction due to sepsis.

Associated Conditions

May accompany other respiratory tract anomalies

Age-Related Factors

Most severe in puppies 6 weeks–6 months old and in puppies from commercial pet shops and humane society shelters.

Zoonotic Potential

Potential zoonotic risk of Streptococcus equi subsp zooepidemicus reported in a single case report.

Pregnancy/Fertility/Breeding

High risk in dogs on extensive medical treatment; especially risky for dogs in overcrowded breeding facilities.

Synonyms

Kennel cough, infectious tracheobronchitis-uncomplicated disease

Abbreviations

• CAV = canine adenovirus
• CDV = canine distemper virus
• CHV = canine herpes virus
• CPiV = canine parainfluenza

Internet Resources

www.cdc.gov/flu/canine/

Client Education Handout Available Online