Coxiella (bacterium)
Coxiella is a genus of Gram-negative bacteria belonging to the order Legionellales and the family Coxiellaceae. The genus contains a single recognized species, Coxiella burnetii, which is the causative agent of Q fever, a zoonotic disease that can affect humans and a variety of domestic and wild animals.
Coxiella burnetii is an obligate intracellular parasite, meaning it can only replicate within the cells of a host organism. It exhibits a unique biphasic developmental cycle, alternating between a small cell variant (SCV), which is highly resistant to environmental stress and responsible for transmission, and a large cell variant (LCV), which is metabolically active and replicates within a parasitophorous vacuole inside the host cell.
The SCV's resilience is attributed to its spore-like properties, allowing it to survive for extended periods in harsh conditions such as drought, heat, and exposure to disinfectants. This characteristic contributes significantly to the persistence of Coxiella burnetii in the environment and facilitates its spread through various routes, including inhalation of contaminated aerosols, ingestion of contaminated materials, and direct contact with infected animals or their products.
Q fever in humans can manifest as an acute or chronic illness. Acute Q fever often presents with flu-like symptoms such as fever, headache, muscle aches, and fatigue. In some cases, it can also cause pneumonia or hepatitis. Chronic Q fever is less common but can lead to serious complications such as endocarditis (inflammation of the heart lining) or granulomatous hepatitis.
Diagnosis of Coxiella burnetii infection typically involves serological testing to detect antibodies against the bacterium. Treatment usually consists of antibiotic therapy, with doxycycline being the most commonly used drug.
The control and prevention of Q fever rely on measures such as vaccinating susceptible livestock, implementing proper hygiene practices, and controlling dust and aerosols in areas where infected animals may be present.