Query Fever
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Q Fever.pdf)
‘Query Fever’ was so named by E.H. Derrick who described an outbreak of a febrile illness that occurred among abattoir workers in 1935. Sir MacFarlane-Burnet and Dr R Freeman isolated a microorganism from guinea pigs that had been injected with blood or urine from Derrick’s patients, an organism now called Coxiella burnetii.
Q Fever has remained a significant occupational hazard amongst farm and abattoir workers. The agent is carried widely in Australia, found in cattle, sheep, goats, dogs, cats, native animals including kangaroos and bandicoots and ticks. Animals are asymptomatic carriers. Transmission to humans may occur by inhalation of contaminated aerosols or dust derived from infected ruminants (the commonest route), by contact with infected animals and contaminated articles such as straw, wool, hair and hides. Products of conception are the most potent source of C. burnetii; and to a lesser degree, faeces and milk. The range of occupations that may expose people to Q fever is therefore much wider than the abattoir industry. Some cases of tick-bite transmission are recorded.
Q Fever Disease in Humans
Q fever has an incubation period of 2-5 weeks. The illness is often asymptomatic or may manifest with acute onset of high fever with muscle pain and severe headache. The acute illness usually lasts 1-2 weeks, however, recovery may be significantly delayed in those with Q fever hepatitis or pneumonia. Complete recovery with immunity is the rule. A small number of patients may relapse years later with chronic endocarditis or granulomatous hepatitis. These complications are usually diagnosed serologically. Between 5-15% of patients develop a post-Q fever chronic fatigue syndrome that may last many months and is not associated with serological activation, in contrast to chronic Q fever. Antibiotic therapy is indicated for acute and chronic disease due to Q fever. Unfortunately, most patients with post-Q fever chronic fatigue do not respond to such therapy.
Prevention of Q Fever
Complete avoidance of the Q fever agent through hygienic measures is not practicable. The availability of an effective Q fever vaccine since 1989, made from killed C. burnetii, has refocussed preventive efforts. Candidates for vaccination are tested for previous Q fever exposure by serological and skin tests. Vaccination is not indicated in people who have a positive result because of a risk of side-effect from the vaccine. Due to lack of information on safety in children, vaccination has been avoided in children under 16 years.
Q Fever Vaccination in the Hunter
The Hunter Area Pathology Service has provided a vaccination service since October 1995. For information regarding this service refer to the Q fever Vaccination Clinic information.
Written by: Dr John Ferguson, Microbiology, HAPS
Written: February 1997
Last Reviewed: January 2005