Ticks on the rise due to climate change

The climate crisis is making it warmer in many ecosystems – and that opens up more habitats for ticks. More ticks mean more infections. In addition, the tick season has been extended, in which the tiny bloodsuckers can transmit bacteria and viruses.

The multiplication of ticks increases the number of Lyme disease: In the last five years, the number of people infected with Borrelia has doubled, says Claudia Traidl-Hoffmann, director of environmental medicine at the University Hospital Augsburg and the Institute for Environmental Medicine in Helmholtz Munich.

Tick ​​season starts earlier

At four to seven degrees, the “Gemeine Holzbock”, as the type of tick especially prevalent in Bavaria is called, becomes lively and hungry. With increasingly mild winters, his “hunting season” is extended, and the first ticks appear as early as February.

The “ordinary wood goat” is almost indistinguishable from its ancestors in the distant past. It likes to be moist and warm, and when it is dry, it retreats into loose leaves and bushes if necessary. It can survive there for years without a blood meal.

Transmission of bacteria and other pathogens

A tick in itself is not a health problem. It is only an intermediate host for pathogens: in addition to Borrelia (the bacteria that cause Lyme disease), this is also the TBE virus, the causative agent of tick-borne encephalitis.

Biology and medicine call such an organism a vector: it transfers pathogens from one host organism to another – in greater numbers due to the climate crisis. When a tick bites to get blood from humans or animals, the borrelia that the tick carries in its gut is released from the gut and becomes active. Heating also affects bacteria: the Borrelia themselves change, that is, they become more active.

The Robert Koch Institute names ticks as currently the most important vectors for the transmission of pathogens to humans and animals. Only the fight against the climate crisis will stop its spread. It is also said that non-native tick species can pave the way for new diseases.

New species of ticks arrive in Germany

The Hyalomma tick has recently been added to the native tick species – a type of tick that is actually native to warmer regions such as the Balkans and the Mediterranean and has been introduced. It is five times larger than the “Common Woodbuck”. Traidl-Hoffmann hypothesizes that it can therefore carry more Borrelia. Exact numbers are not yet available.

However, hyaloma ticks can open the way for diseases that are not yet widespread in Germany: they can transmit tick fever or the so-called Crimean-Congo virus. However, the disease still occurs only in the remote steppe regions of Central Asia and Africa.

Other disease vectors such as malaria mosquitoes also migrate

In the climate crisis, ticks are in the “best company” with other animals: Claudia Traidl-Hoffmann names the malaria mosquito that already exists in Europe. Fortunately, the causative agent of malaria that can transmit it has not yet settled here.

The Asian tiger mosquito is just making its home in the Rhine Valley, and it could also transmit new viruses: dengue fever is its “specialty”. One case of West Nile virus transmission has also been reported in Germany; a disease previously classified as a tropical disease.

The climate crisis is a health crisis

Environmental doctor Traidl-Hoffmann advises thinking more about tropical pathogens in the future for infections of unclear cause. However, this still requires some education and information about planetary health. Both in the training of medical students and in any other field of healthcare.

Finally, it must be understood that “all areas of our society, our public life, and especially our health are affected by the climate crisis”.

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