inflammation of the inner lining of the heart), which can occur months or decades following the infection. It is usually fatal if untreated. However, with appropriate treatment, the mortality falls to around 10%. Diagnosis
Diagnosis is usually based on serology (looking for an antibody response) rather than looking for the organism itself. Serology allows the detection of chronic infection by the appearance of high levels of the antibody against the virulent form of the bacterium. Molecular detection of bacterial DNA is increasingly used. Contrary to most obligate intracellular parasites, Coxiella burnetii can be grown in an axenic culture, but its culture is technically difficult and not routinely available in most microbiology laboratories.Q fever can cause endocarditis (infection of the heart valves) which may require transoesophageal echocardiography to diagnose. Q fever hepatitis manifests as an elevation of alanine transaminase and aspartate transaminase, but a definitive diagnosis is only possible on liver biopsy, which shows the characteristic fibrin ring granulomas. Prevention
Research done in the 1960s–1970s by French Canadian-American microbiologist and virologist Paul Fiset was instrumental in the development of the first successful Q fever vaccine.Protection is offered by Q-Vax, a whole-cell, inactivated vaccine developed by an Australian vaccine manufacturing company, CSL Limited. The intradermal vaccination is composed of killed C. burnetii organisms. Skin and blood tests should be done before vaccination to identify pre-existing immunity, because vaccinating people who already have  immunity can result in a severe local reaction. After a single dose of vaccine, protective immunity lasts for many years. Revaccination is not generally required.
It is considered a good agent in part because its ID50 (number of bacilli needed to infect 50% of individuals) is considered to be one, making it the lowest known. In animals
Q fever can affect many species of domestic and wild animals, including ruminants (cattle, sheep, goats, bison, deers...), carnivores (dogs, cats, seals...), rodents, reptiles and birds. However, ruminants (cattle, goats and sheep) are the most frequently affected animals, and can serve as a reservoir for the bacteria. Clinical signs
In contrast to humans, even though a respiratory and cardiac infection could be experimentally reproduced in cattle, the clinical signs mainly affect the reproductive system. Q fever in ruminants is therefore mainly responsible for abortions, metritis, retained placenta and infertility. The clinical signs vary between species. In small ruminants (sheep and goats), it is dominated by abortions, premature births, stillbirths and the birth of weak lambs or kids. One of the characteristics of abortions in goats is that they are very frequent and clustered in the first year or two after contamination of the farm. This is known as an abortion storm.In cattle, although abortions also occur, they are less frequent and more sporadic. The clinical picture is rather dominated by non-specific signs such as placental retentions, metritis and, consequently, fertility disorders. Epidemiology
With the exception of New Zealand, which is currently free of Q fever, the disease is present throughout the world. Numerous epidemiological surveys have been carried out.