Throughout history, human migration has facilitated the spread of pathogens. In the 1970s when long-distance air travel became more affordable, for the first time in human history, the average person could travel across the world in just a few hours, and just as quickly return home. This new and sudden increase in human migration directly led to the emergence of a new field of medicine - Travel Medicine. Classic travel medicine revolves around preparation before departure, which for someone living in Europe mostly includes prevention of tropical diseases (such as malaria prophylaxis or the yellow fever vaccination depending on the destination) and ensuring you are up to date on the basic vaccinations (e.g. the measles vaccination). But what if tropical diseases are no longer isolated to the tropics? Just like humans are on the move more than ever, so are other carriers (vectors) of disease, such as mosquitos or ticks. And climate change directly benefits these vectors - let’s look at a local example.
A battle already lost
If you get bitten by a tick in Switzerland, you may then be at risk for a tick-borne disease. One such disease, Tick-borne encephalitis (TBE), is caused by a virus that is carried by ticks and affects the central nervous system (the brain and spinal cord). TBE in Switzerland is a much bigger deal than most people are aware. While the disease was first reported in the 1970s in just the northeastern part of the country, it has spread widely since and now Switzerland is one of the most highly endemic countries in Europe. It is even on the higher side of what is observed in the world and every canton (except for Ticino) is considered a risk area. Unfortunately, because it’s still a relatively new issue in Switzerland, awareness is low – a recent study found that, among TBE endemic countries in Europe, TBE awareness was lowest in Switzerland1.
Lyme disease or the newly discovered Alongshan virus (ALSV) are also diseases spread by ticks and are all are a much bigger deal than most people are aware. Because of the risk of tick-borne diseases, if you feel sick after spending time outside or after being bitten by a tick, it is best to visit a doctor. Many of these diseases initially present with flu-like symptoms (one in three people with Lyme disease will additionally develop a bullseye rash). Treatment is key: Lyme disease has antibiotic treatment options, and while TBE or ALSV do not have a specific antiviral therapy, supportive care is available.
What is causing this huge increase of tick-borne diseases in Switzerland?
As always, there are many factors contributing to this increase in tick-borne diseases in Switzerland, but one cannot overstate the impact of climate change. The winters are not quite as cold, which increases tick egg production2. Additionally, warmer weather can lead to more active ticks3. And since there is a longer warm season, more people are outside longer (not just July and August), thus increasing the time they can be exposed to ticks. It is important to remember that ticks are no longer just found in wooded areas but also in bushes and parks in cities - "outdoors" includes outdoors in cities too.
At this point there is not much we can do to prevent the spread of infected ticks in Switzerland. If Switzerland gets too hot in the summers, ticks may move further north, but more modelling is required to see how this may play out4. In the meantime, if we can’t control the spread/movement of infected ticks in the environment, then we really need to protect ourselves.
The best ways to do this are
1) to get the TBE vaccine,
2) use tick spray and
3) cover up your skin as much as you can while outside in the Spring/Summer (March-November).
It is recommended that everyone who lives in a tick risk region be vaccinated against TBE (currently every canton except Ticino)5. For one year of protection, two vaccinations are required, with an interval of at least one month. For long-term protection, a third dose is needed after about a year. After that, if the risk remains, a booster vaccination is recommended every 10 years.
To help prevent tick-borne illnesses, always check your skin and clothing for ticks after spending time in wooded or forested areas. Light-colored clothing makes it easier to spot ticks. Don't forget to check pets, like dogs, cats, and horses, as they can also carry ticks. If you find one, remove it immediately using tweezers, grasping the tick as close to your skin as possible and pulling it out gently and steadily. After removal, disinfect the bite area. If you experience a fever or any other symptoms after a tick bite, be sure to consult a doctor.
References
- "TBE in Switzerland is a much bigger deal than most people are aware of" Interview with Dr. Kyra Zens https://reisemedizin.uzh.ch/en/blog/interview_dr_kyra_zens_part_1
- https://climate-adapt.eea.europa.eu/en/observatory/evidence/health-effects/vector-borne-diseases/TBE-factsheet
- Lukan, M. et al., 2010, Climate Warming and Tick-borne Encephalitis, Slovakia, Emerging Infectious Diseases 16(3), 524–526. https://doi.org/10.3201/eid1603.081364
- https://www.mdpi.com/2673-4931/26/1/18
- https://www.bag.admin.ch/bag/en/home/krankheiten/krankheiten-im-ueberblick/fsme.html