Which diseases can be caused by a tick bite in Switzerland and how dangerous are they?
In our latitudes, ticks can transmit various pathogens to humans. The most common are Lyme disease, caused by the bacterium B. burgdorferi, and tick-borne encephalitis, caused by the TBE virus. Likewise, tularemia (rabbit fever) can be transmitted by ticks. Other diseases such as ehrlichiosis or rickettsiosis are rarities.
Lyme disease
According to estimates by the Federal Office of Public Health (FOPH), about 5-30 percent of ticks throughout Switzerland are infected with Borrelia, and 8,000-15,000 people contract Lyme borreliosis each year. The disease manifests itself in very different ways (see below) and can be treated with antibiotic therapy and – if diagnosed and treated in time – also completely cured.
Tick-borne encephalitis
Approximately 0.5 percent of all ticks in Switzerland are carriers of TBE viruses. The risk areas have expanded in recent years. Currently, all regions in Switzerland are affected except for Ticino and Geneva. In Switzerland, about 200-400 people per year contract TBE. There is no effective therapy against TBE. Symptoms can only be alleviated.
Tularemia or rabbit fever
Rabbit fever is caused by the bacterium Francisella tularensis. Rabbit fever is very rare, but in recent years the number of cases in Switzerland has been increasing. Antibiotic therapy can be initiated if the diagnosis is appropriate.
Earlier this year, an emerging virus transmitted by ticks was reported. What is known about it so far?
The Alongshan virus (ALSV) could be detected in ticks in Switzerland in 2021/2022. However, the effects of this virus on humans have not yet been conclusively clarified. It was first detected in China in 2017 in patients with a history of tick bites and symptoms of TBE virus. It has never been isolated in a patient in Switzerland. Specific tests are not yet available, but in suspected cases, viral metagenomic sequencing can be used to clarify whether ALSV is present.
What are the symptoms to look out for after a tick bite and what should you do if they occur?
Lyme disease symptoms
After a tick bite with transmission of Borrelia, a migratory redness (erythema migrans) may occur a few days later. This is an inflammation of the skin in the area of the sting, which expands in a ring shape in the course and fades again centrally, similar to the image of a target. This skin manifestation must be distinguished from the local and harmless skin reaction, which typically occurs only just around the sting site and does not extend beyond 5 cm.
In case of a skin reaction typical for Borrelia, a physician should be consulted in order to initiate antibiotic therapy. In rare cases, different symptoms may appear several weeks to years after transmission of Borrelia. Joint inflammation may occur, in this case the knee joint is usually affected. Further, cardiac arrhythmias or inflammation of the nervous system may occur. In these cases, a physician should be consulted to diagnose or rule out Lyme disease. If confirmed, the physician will recommend antibiotic therapy.
Symptoms of early summer meningo encephalitis
TBE typically occurs in two phases: The first phase lasts seven to fourteen days after the tick bite. During this time, flu-like symptoms such as headache, fever, fatigue or joint pain may occur, but they disappear completely after a few days. For a small proportion of patients, after a symptom-free interval, a second phase occurs in which the nervous system is affected: Meningitis or cerebral inflammation, paralysis of the facial nerves, arms or legs. Severe courses can lead to permanent damage or even death.
Rabbit fever symptoms
In hare fever, ulcers occur in the area of the bite site within about ten days after the tick bite, with concomitant enlarged lymph nodes in the region of the bite site. If these symptoms are present, a physician should be consulted to initiate antibiotic therapy.
