Contributor: Arjumand B. Syed
Q fever (Australian fever, query fever, Derrick-Burnet disease, Queensland fever, Queensland tick fever,  Queensland tick typhus, Coxiella burnetii infection) is a febrile rickettsial infection caused by Coxiella burnetii. This infection was first described in abattoir workers in Australia. Q fever is endemic world wide with the exception of New Zealand and Antarctica. Q fever is a zoonosis. The primary sources of human infection are infected cattle, sheep, and goats. However, infected cats, rabbits, and dogs have also been shown to transmit Coxiella burnetii to humans. The extensive wildlife reservoir for Coxiella burnetii include mammals, birds, and ticks. In the infected female mammal, Coxiella burnetii localize to the uterus and the mammary glands; infection is reactivated during pregnancy, and high concentrations of Coxiella burnetii are found in the placenta. At parturition, Coxiella burnetii is dispersed as an aerosol, and infection follows inhalation of these organisms by a susceptible host. Infected female animals shed the organism in milk for weeks or months after parturition. In rare instances, human-to-human transmission has followed childbirth by an infected woman or autopsy on an infected patient.Coxiella burnetii has been transmitted via blood transfusion. The persons at risk are abattoir worker, veterinarians, and those who vocationally and avocationally come into contact with infected animals. Exposure to infected new born animals or to infected products of conception poses greatest risk. The ingestion of contaminated milk in some areas is probably a major route of infection. Pneumonia is a manifestation of acute Q fever. Sometimes optic neuritis develops.