An infection caused by Coxiella burnettii, a micro-organism that is widespread in nature, infesting cattle and sheep. It is contracted by humans in rural areas from direct contact with infected animals or inhalation of dust from contaminated premises. There is a flu-like illness, which may be complicated by pneumonia or endocarditis (infection of the lining of the heart and heart valves). It can be treated with the antibiotic tetracycline.
| ICD-9 | 083.0 | |
|---|---|---|
| eMedicine | med/1982 ped/1973 | |
| MeSH | C01.252.400.755 | |
Q fever is a zoonosis caused by the strictly intracellular, gram negative bacterium Coxiella burnetii which proceeds asymptomatic and self-limiting in 60% of the cases.
History
It was first described by Edward Holbroock Derrick in abattoir workers in Brisbane, Queensland, Australia.
In 1937 the bacterium was isolated by Frank Macfarlane Burnet and Freeman from one of Derrick’s patients for the first time and identified as Rickettsia-species.
Manifestations
The most common manifestation is flu-like symptoms with abrupt onset of fever, malaise, severe headache, myalgia (muscle pain), loss of appetite, dry cough, pleuritic pain, chills, confusion and gastro-intestinal symptoms such as nausea, vomiting and diarrhoea.
During the course, the disease can progress to an atypical pneumonia, which often results in a life threatening acute respiratory distress syndrome (ARDS), whereby such symptoms usually occur during the first 4-5 days of infection.
Less often the Q fever causes (granulomatous) hepatitis which becomes symptomatic with malaise, fever, liver enlargement (hepatomegaly), pain in the right upper quadrant of the abdomen and jaundice (icterus).
The chronic form of the Q fever is virtually identical with the inflammation of the inner lining of the heart (endocarditis), which can occur after months or decades following the infection.
Appearance and incidence
The pathogenic agent is to be found everywhere except Antarctica and New Zealand.
Men are slightly more often affected than women, which most likely is attributed to different employment rates in typical professions.
"At risk" occupations include:
veterinary personnel stockyard workers farmers shearers animal transporters laboratory workers handling potentially infected veterinary samples or visiting abattoirs people who cull and process kangaroos hide (tannery) workers.Diagnosis
Diagnosis is usually based on serology (looking for an antibody response) rather than looking for the organism itself.
Q-fever can cause endocarditis (infection of the heart valves) which may require transoesophageal echocardiography to diagnose.
Treatment
Treatment of the acute Q fever with antibiotics is very effective and should take place in consultation with the infectiologist.
Prevention
Q fever is effectively prevented by intradermal vaccination using a vaccine composed of killed Coxiella burnetii organisms.
In 2001, Australia introduced a national Q fever vaccination program for people working in "at risk" occupations.
Other
Because of its route of infection it can be used as biological warfare agent.
Literature
Q Fever, "Clinical Microbiology Reviews", Oct. 1999, 518 - 583
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