Ticks in Switzerland – Infected with the Alongshan virus: How bad is it?

Ticks transmit more diseases than previously thought. What we currently know about it.

Have the number of bacteria and viruses that can be transmitted by ticks increased compared to before? There is no conclusive answer to this: For the first time ever, a study from Switzerland systematically examined ticks for pathogens. The researchers sequenced the entire genetic material of over 10,000 animals from ten cantons and compared the sequences with large biodatabases. In this way, they discovered the genomes of at least seven virus families.

Using targeted PCR tests, they also found bacteria in almost every tick examined. But that doesn’t have to mean that the frequency of the pathogens has increased, says virologist Cornel Fraefel, who was involved in the study: There is no information from the past with which one could compare the values.

How dangerous is the new Alongshan virus ALSV for humans? The new Alongshan virus is associated with symptoms typical of colds such as fever, headache, muscle or joint pain. A Chinese study also reported more severe symptoms such as fatigue or depression. However, doctors are still very cautious about drawing conclusions here. They say the virus appears to be “associated” with these symptoms. It is not yet clear whether this is also the cause.

ALSV is twice as common as the TBE virus, against which you can be vaccinated. What about vaccination for ALSV? This is a long way away – especially since it is not clear how relevant the Alongshan virus actually is to health. The researchers in Zurich are currently in the process of developing serological tests to identify antibodies against the Alongshan virus in patients’ blood. Then you know more.

Are animals affected by ALSV in addition to humans? In China, the virus has also been found in sheep and cattle, but they tolerate it well. It is conceivable that ALSV also has a natural reservoir in Europe. But according to Cornel Fraefel, that is a hypothesis.

Does the emergence of the Alongshan virus have something to do with climate change, or was it simply not known before? The Algonshan virus was first discovered in China in 2017. According to researchers at the University of Zurich, it has probably been circulating for a long time, not only in China but also in Europe. That means you simply didn’t know it.

At the same time, however, the conditions for disease-transmitting animals such as mosquitoes or ticks – in science they are called “vectors” – have improved due to climate change. This means that these animals transmit more diseases and do so more efficiently, and thanks to the mild winters they are increasingly able to gain a foothold in northern countries. This also applies to ticks: in 2023, the African Hyalomma tick, which can transmit tropical fever diseases, was detected in Switzerland for the first time.

How is it that ticks in urban environments carry many more pathogens than others? The study demonstrated this urban-rural divide exclusively for Borrelia – the bacteria that leads to Lyme disease. Ticks in urban areas are four times more likely to carry Borrelia than in rural areas. However, the researchers cannot explain why this is the case.