Recent years have seen a higher number of tick-borne encephalitis (TBE) cases than usual. In 2021, Estonia recorded 82 cases of TBE; by 2023, that number had more than doubled to 209. However, last year, this growth trend stalled, and the number of cases declined again.

While the number of ticks used to vary by region, these days, the difference is no longer as pronounced.

"The taiga tick (Ixodes persulcatus) is more prevalent in Southern and Eastern Estonia, but the castor bean tick (Ixodes ricinus) is everywhere," noted Kaarel Sammet, a zoologist at the Estonian University of Life Sciences (EMÜ).

"Typically, they're active by around mid-April," Sammet said. "When ground temperatures reach over 5 or 6 degrees Celsius (C) and the snow has melted, that's when they start to become active."

Ticks are increasingly being found in urban environments and backyard gardens as well, particularly castor bean ticks. Sammet says this can be credited to the fact that recent winters in Estonia have gotten milder.

If winters should continue to warm, Estonia may expect to see new tick species in the future — in addition to the six already present in the country.

"But the ones that attack humans are taiga and castor bean ticks," the zoologist explained. "Generally, depending on their development stage, they'll inhabit different environments — nymphs and larvae are on the ground, but adults will usually climb up grass stalks."

Ticks actually spread Lyme disease more than TBE, but a vaccine currently only exists for TBE. Lyme disease can be treated with antibiotics, but for TBE prevention, doctors recommend vaccination.

The majority of Lyme disease cases occur between May and October. Since the incubation period for TBE is a couple of weeks long, however, people usually seek medical help for cases of encephalitis as soon as ticks are active again in the spring, and April and May are the busiest months for doctors in terms of vaccinations.

"Interest in vaccination against TBE has clearly increased in recent years," noted Anne Kallaste, director of the Department of Infectious Diseases at Tartu University Hospital (TÜK).

"Around 60,000 doses of the TBE vaccine were administered in 2023, but last year, that number had risen to more than 100,000 doses already," she confirmed. "This is clearly a growing trend."

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