Coxiella burnetii

Question 1

What are the bacteriological features of Coxiella burnetii?

Answer 1

• In a former life was classified with the rickettsia but no more!
• Short pleomorphic gram negative bacillus, obligate intracellular (macrophage)
– Need cell culture to grow in lab
• Highly infectious at very low doses
• Can form spores which can survive for prolonged periods outside of host
• Causes Q fever

Question 2

What is Q fever?

Answer 2

• Worldwide zoonosis. Reservoir: Cattle, sheep, goats
SPREAD: Humans = incidental hosts
• Usually acquired from occupational exposure to infected animals
– Farmers, abattoir workers, vets
– Inhalation of contaminated aerosols arising from the placenta or parturient fluids of infected livestock
• Unpasteurised dairy products (less common)
• Laboratory exposure
• No human to human transmission (only very rare reports)

Question 3

What is the clinical presentation of Coxiella burnetii?

Answer 3

Infection
Very variable

1. Asymptomatic / mild symptoms

2. Acute infection
•	Flu-like illness (headache / fever)
•	Pneumonia (50%) 
•	Hepatitis
•	Pericarditis
•	Meningoencephalitis
•	Usually, there is no rash

3. Chronic infection
   • 1-5% infected people
   • Commonest manifestation – culture negative endocarditis
   • Hepatitis, osteomyelitis, vascular graft infection
   • More likely if
   – pregnant, immunocompromised, underlying valvular or vascular disease

Question 4

What is the diagnosis of Coxiella burnetii?

Answer 4

– Serology
– Nucleic acid amplification testing (NAAT) (not commonly available)
– Culture: biosafety level 3 containment due to extreme infectivity

Question 5

What is the treatment of Coxiella burnetii?

Answer 5

• Acute: Doxycycline

* Chronic: Combination therapy (e.g. doxycycline + rifampicin) for a prolonged period (year? Lifelong?)

Question 6

What’s you diagnosis? 52 year old farmer presents with 6 week history of fever, weight loss and night sweats.
On examination by his GP – new mitral valve murmur heard

Answer 6

Q fever