Pathogen and transmission
Q fever is an acute disease that is caused by the Coxiella burnetii bacterium. The natural reservoirs for these bacteria are cattle, sheep, goats, dogs, cats, a few wild animals and ticks. Infected animals often show no symptoms of disease, but will excrete the pathogen in their faeces, urine and milk. The birth products (such as the placenta) of farm animals can be particularly highly infectious.
Most cases of Q fever infection in humans occur through inhaling dust containing the pathogen or through direct contact with an infected animal. The bacteria can also be transmitted through contact with contaminated products or foods from such animals (such as unpasteurised milk) or – in very rare cases – through the bite of an infected tick.
Pathology
In many people Q fever will cause only mild flu-like symptoms or no symptoms at all. Any such symptoms will also generally disappear of their own accord after one or two weeks. In about 50 per cent of cases, however, the disease will develop two or three weeks after infection – usually with the sudden onset of fever, chills, sweats, fatigue and headaches. These symptoms are often also accompanied by a dry cough and chest pains. Some cases may also see the development of complications such as carditis, pneumonia or hepatitis – inflammations of the heart, the lungs or the liver respectively.
Q fever is generally treated with a two-week course of antibiotics. This treatment is important, to prevent the disease becoming a chronic condition.
Distribution and frequency of occurrence
The bacterium which causes Q fever is found almost worldwide. In Switzerland, the reporting of cases of Q fever has been mandatory (again) since November 2012. Some 40 to 100 such cases are reported every year. In addition to isolated cases, outbreaks of Q fever can also occur.
Prevention
Most of the actions to prevent Q fever infection are in the veterinary medicine field. One of the key issues here is to identify any infections in farm animals as promptly as possible. This is also why the owners of such animals must report any abortion of any cattle, sheep or goats to their veterinary surgeon.
In some countries in which the disease is well established, a vaccine is available, though this is not currently approved in Switzerland. Such vaccination is recommended for persons employed in laboratories that work with the bacterium and for those who may come into contact with infected animals (such as veterinary surgeons or abattoir personnel).