Q Fever in humans, domestic animals and wildlife

Q Fever is a zoonotic disease caused by Coxiella burnetii, which can infect a wide range of host species, including humans, domestic animals and wild animals. Domestic livestock are the primary reservoir for human infections and humans are usually considered incidental hosts, with human-to-human infection being exceedingly rare. Because livestock are reservoirs, at-risk groups for Q fever have been considered to be abattoir workers, veterinary personnel, farm workers, livestock handlers and wool shearers. However, there has been an increasing prevalence of human cases that have a history of direct or indirect exposure to wildlife, pointing towards likely wildlife reservoirs. Coxiellosis can be diagnosed using indirect and direct methods. Specific antibodies against C. burnetii are usually detectable within 1–3 weeks of infection in humans and experimental animal models. Anti-phase 2 immunoglobin M (IgM) and immunoglobin G (IgG) antibodies appear first in the early stages of acute infections, followed by a delayed and less pronounced phase 1 IgM and IgG antibody response. Interpretation of polymerase chain reaction (PCR) and serology test results are useful for estimating the date of onset of symptoms or clinical signs and the date of exposure. This allows a time window of exposure to be determined and may assist with identification of likely sources of infection.