Kennel cough (canine infectious tracheobronchitis) is a highly contagious respiratory illness primarily observed in dogs. While this illness mainly affects canines, the causative bacteria is zoonotic, meaning it can transfer from animals to people. The primary agent of concern for human health is a specific bacterium. Human infection remains a rare event, particularly for individuals who are otherwise healthy.
Zoonotic Nature of the Kennel Cough Pathogen
The potential for kennel cough to cross the species barrier centers on the bacterium Bordetella bronchiseptica. This gram-negative organism is a close relative of Bordetella pertussis, which causes whooping cough in humans. Bordetella bronchiseptica is commonly found in the respiratory tract of various mammals, including dogs and cats, where it acts as a pathogen causing respiratory disease.
Transmission from an infected animal to a human typically occurs through the inhalation of aerosolized respiratory droplets. This happens when an infected dog coughs or sneezes, releasing the bacteria into the air. Direct contact with an animal’s contaminated secretions or fomites can also facilitate transfer. The bacterium is considered an opportunistic pathogen in humans, meaning it rarely causes illness in people with robust immune systems.
The likelihood of contracting the infection is low, but transmission is generally associated with close, prolonged contact with an animal actively shedding the bacteria. Understanding the pathogen’s ability to jump hosts is separate from describing the resulting human illness, which presents differently than the disease in dogs.
Human Presentation: Identifying Symptoms
When Bordetella bronchiseptica causes illness in humans, the symptoms are generally respiratory and often milder than the severe, distinctive “honking” cough seen in canine cases. The clinical presentation frequently resembles a common upper respiratory tract infection or mild tracheobronchitis. A persistent, dry hacking cough is a common sign of infection in humans.
Other symptoms reported include a mild fever, sore throat, rhonchi, and difficulty breathing in severe cases. The resulting condition can sometimes be confused with whooping cough, caused by the related B. pertussis, as it may present with a whooping-cough-like syndrome in otherwise healthy individuals. The illness often resolves on its own in healthy individuals, and the incubation period is typically short.
Risk Factors and Medical Management
Infection with Bordetella bronchiseptica is predominantly a concern for people with compromised immune systems. High-risk groups include those undergoing chemotherapy, organ transplant recipients, individuals with HIV, and those with chronic lung diseases like cystic fibrosis. Infants and the elderly are also more susceptible due to their less-developed or waning immune defenses.
If a person with known risk factors develops respiratory symptoms after contact with a sick animal, a doctor should be consulted. Diagnosis often involves culturing the bacteria from a respiratory sample, such as sputum or a bronchial wash. Treatment for a confirmed infection often includes supportive care, though antibiotics may be necessary, especially in vulnerable populations.
While macrolides, such as azithromycin, are often used for community-acquired pneumonia, Bordetella bronchiseptica can show resistance to this class of drug. Effective antibiotic options often include trimethoprim-sulfamethoxazole or a fluoroquinolone, but the appropriate course must be determined by a healthcare professional. Prevention for people at higher risk should include diligent hand hygiene and avoiding direct contact with pets showing signs of respiratory illness.