VIII.114 - Q Fever

Summary

The “Q” in Q fever stands for “query,” the designation applied by E. H. Derrick to an acute illness with fever and severe headache of unknown cause occurring in abattoir workers and dairy farmers in Queensland, Australia, in 1935. Despite the discovery of the causative agent, a rickettsia-like organism, this unenlightening name has remained current, although an alternative is abattoir fever. Q fever, occurring in epidemics in military personnel stationed in the Balkans and Italy during World War II, was known as Balkan influenza or Balkan grippe.

Q fever is caused by infection with Coxiella burnetii, previously known as Rickettsia burnetii, and is the sole member of the genus Coxiella, family Rickettsiaceae. It was initially confused with viruses, but though C. burnetii is an obligate intracellular parasite, it has a true bacterial cell wall.

Q fever is a zoonosis of worldwide distribution, and many species of animals, birds, ticks, and other biting insects are natural hosts. In animals, naturally acquired infection appears to be asymptomatic so that Q fever is not of any economic significance to farmers. Transmission to humans occurs via inhalation of contaminated dust while infected animals, carcasses, or animal products are being handled; via laboratory accidents; and sometimes via tick bite and the consumption of unpasteurized milk. Asymptomatic infection is common. Illness may take two forms. Acute Q fever is usually a self-limiting febrile flulike illness or atypical pneumonia lasting up to 4 weeks. Untreated, the fatality rate is less than 1 percent. Chronic Q fever may develop months to years later, presenting as endocarditis and/or hepatitis. Endocarditis usually occurs in those with preexisting heart valve disease; untreated, it is usually fatal.