Ticks can't climb mountains or cross seas on their own even with warmer weather: being parasites, they travel longer distances on host animals. In Scandinavia and the Alps, climate warming allows roe deer and other hosts to move further north and to higher altitudes, carrying ticks to places where they can now survive.
Across much of the rest of Europe, non-climate factors may be just as relevant. Growing deer populations, expanding forests, and abandoned farmland have created more connected, tick-friendly habitats.
The South is not any safer. Although some ticks, like the common sheep tick (Ixodes ricinus), need moisture and become less active during very hot, dry weather, the Mediterranean has its own mix of ticks, like the heat-tolerant, sun-seeking Hyalomma marginatum or Dermacentor marginatus. As conditions change, the risk may shift from one species to another rather than disappear altogether.
On the move
The changes are easier to see at the edges of the ticks' typical ranges. The common sheep tick already ranges from North Africa to Scandinavia, but new sightings sit far behind the Arctic Circle and higher up Alpine valleys that were once too cold for it to survive.
Then there is Hyalomma marginatum: a large, fast-moving Mediterranean tick. It can be carried north by migratory birds, although the occasional find doesn't mean it has permanently settled.
The issue is, both Ixodes ricinus and Ixodes persulcatus can carry both Lyme disease and tick-borne encephalitis (TBE), and the ECDC has namedHyalomma marginatum as the main carrier of Crimean-Congo hemorrhagic fever.
A changing tick map, however, is not the same thing as a changing disease map.
“The presence of ticks alone does not mean that they are infected or able to transmit pathogens,” said Céline Gossner, head of the ECDC's section for food-, water-, vector-borne and zoonotic diseases. Rising tick-borne disease case numbers can also have several causes: more exposure, but also better surveillance, diagnosis, and awareness, meaning more cases are being caught.
The tick on your leg
Still, caution is advised. All these moving ticks can seem rather abstract, until you find a parasite under your shirt that is already attached to your skin.
Jānis Graudiņš, an entomologist at Latvia's scientific research centre BIOR, explains that after hatching, ticks pass through three active life stages: larva, nymph, and adult.
“They all look the same, only in different sizes,” he told us. A larva finds a host, feeds, drops off, and becomes a nymph. After another blood meal, the nymph becomes an adult – “the one we usually see.”
Nymphs cause most Lyme disease cases – mainly because they're easy to miss. “They are much smaller than adults, so they are harder to find,” Graudiņš said. With Lyme disease, he explains, the risk rises when an infected tick remains attached for longer.
There are also plenty of myths surrounding ticks. For one, ticks don't jump off trees. Most ticks don't chase their hosts; they use an ambush method called questing, where they wait on plants and grab a passing animal or human, Graudiņš explained.
Their eyes are very basic, while some species don't have eyes at all. Instead, they sense movement, vibrations, and the potential host's breath. Some may move along the ground towards what they've sensed, like the Mediterranean one, which actively moves towards its next meal.
Another persistent myth concerns removal: that leaving the tick's head in the skin increases the risk of infection with the disease the tick is carrying. Graudiņš says the head is simply more like a splinter and may cause local irritation.
“The main thing is to get the tick out as quickly as possible,” he explained. “Better leave the head in than keep the tick attached to your skin.”
How to anti-tick
The best method is to use a plastic tick removal card or sharp tweezers. Do not squeeze the tick's belly (it can release even more poison into the wound) – instead, aim for the head.
Tick bites can be prevented, Gossner says: use repellent, wear long sleeves and trousers in tick habitats, and do tick checks afterward. In areas where TBE is present, vaccination is the most effective protection against the disease. But there is currently no human vaccine for Lyme disease.
So why do ticks exist?
Though they're hard to love, ticks are part of our ecosystem. They feed on wild animals, become food for some birds, amphibians, and other small animals, and form a part of wider host-parasite systems.
“We humans are fixated on what value an animal brings,” Graudiņš said. But ticks “are trying to survive, adapt, and pass their genes to the next generation.”
They don't put us in danger deliberately, he added, “but it still works out badly for us.”