Q fever, known as coxiellosis in animals, is a disease that can be transmitted from animals to humans (zoonosis). It is widespread throughout the world and is detected in different animal species, such as domestic and wild mammals (sheep, goats, cattle, cats, dogs, deer and rodents). The pathogen causing the disease is the Coxiella burnetii bacterium. Q fever is a particularly contagious zoonosis because only a few bacteria are needed to infect a human.
The first description of the disease can be traced back to Brisbane in Australia in 1935. An unexplained fever in slaughterhouse employees prompted scientists to name the syndrome “query fever” (unexplained fever). Simultaneously, a team from Montana (USA) isolated the agent responsible for a similar pathology (Rocky Mountain Fever). Scientists went on to demonstrate that the pathogen involved in these two pathologies were the same, and called it Coxiella burnetii after the scientists responsible for its discovery, Dr Herald Cox (United States) and Dr Frank Macfarlane Burnet (Australia).
Transmission of the infection is mainly by airborne inhalation of airborne particulate matter. Farrowing products, mainly relating to sheep and goats, are the source of human contamination because these products contain many bacteria. If left in the environment and if they dry up, they can become a source of infectious aerosols.
The main clinical sign of Q fever in livestock is abortion. In small ruminants (sheep, goats), in farms that have never been in contact with the disease, this abortion rate can be extremely high (up to 80% of animals in gestation). In cattle, there are fewer abortions but fertility problems and metritis are observed.
Infection with Coxiella burnetii is also described in pets (cats and dogs) where it causes abortion, and in wild mammals (cervids, foxes, rodents, marine mammals) where the clinical manifestation is less defined.
The extent of Q fever in humans has been recently highlighted due to an epidemic in the Netherlands. About forty-four thousand human cases were diagnosed between 2007 and 2010. This human contamination was caused by contaminated goat farms.
In humans, the signs of Q fever in its acute form are usually isolated febrile episodes, pneumonia, hepatitis, which respond well to antibiotic treatment and heal most often without sequelae.
In some subjects with aggravating factors (valvulopathy, compromised immune patient, pregnant woman) the infection can be poorly controlled; it becomes chronic and requires significant medical care.
Q fever is a disease that requires mandatory notification whether the infection is human or animal.
In humans | mandatory declaration in Flanders and in Wallonia.
Some professional categories (veterinarians, slaughterhouse staff, farmers, … ) may be at higher risk of exposure. It may be useful to know if an infection is present on the farm. The C. burnetii species is classified as a potential agent for bioterrorism.
