Q fever is an infectious disease caused by the bacterium Coxiella burnetii. This bacterium is a zoonotic pathogen, meaning it can naturally transfer from animals to humans.
Modes of Transmission
The most frequent method of Q fever transmission is through airborne particles. Humans can inhale dust or aerosols contaminated with Coxiella burnetii, particularly in environments where infected animals are present. The bacterium can remain viable in dust for extended periods and can be carried by wind over significant distances, sometimes up to 18 kilometers.
Other, less common transmission routes include direct contact with infected animals or their bodily fluids. Consuming unpasteurized dairy products, such as milk or cheese, can also lead to infection. Tick bites are a rare mode of transmission, as is human-to-human spread, which is associated with contact with birth products or, in infrequent instances, blood transfusions.
Common Sources of Infection
Livestock, particularly sheep, goats, and cattle, serve as the primary animal reservoirs for Coxiella burnetii. These animals can carry the bacterium without showing symptoms of illness. The bacteria are shed in high concentrations in birth products, such as the placenta and amniotic fluid.
The bacterium is also excreted in the feces, urine, and milk of infected animals. These contaminated bodily fluids and birth products can then contaminate soil and dust in the environment. The small-cell variant form of Coxiella burnetii is highly resistant to heat and drying, enabling it to persist in the environment for weeks.
Populations at Higher Risk
Those with occupational exposure, such as farmers, veterinarians, and abattoir workers, are susceptible due to their close contact with livestock. Laboratory personnel who handle the bacterium or potentially infected animal samples also face increased risk.
Individuals residing near livestock farms or in areas experiencing known outbreaks are also at higher risk of exposure through contaminated air and dust. Pregnant women, people with pre-existing heart valve conditions, or those with weakened immune systems are at a greater risk of developing more severe or chronic forms of the disease if infected.
Steps to Prevent Transmission
To reduce the risk of Q fever transmission, avoid contact with birthing animals, as they shed high concentrations of the bacterium. Practicing thorough handwashing with soap and water after handling any animals or their products is also a preventive measure.
Wearing personal protective equipment, such as P2/N95 masks and gloves, is recommended when working with animals or potentially contaminated materials. Proper disposal of animal waste and birthing products can help minimize environmental contamination. Consuming only pasteurized dairy products can prevent infection through this route. In some countries, like Australia, a vaccine is available and recommended for high-risk occupational groups to prevent Q fever.