Lithuania recorded a surprising 15,254 cases of Lyme disease in 2023 – a fivefold increase from the 2,896 reported infections caused by Borrelia bacteria the previous year. The dramatic spike has prompted questions about the cause, with the National Public Health Centre (NVSC) offering several explanations.
Milda Žygutienė, an entomologist at the NVSC, told LRT.lt that the sharp rise in cases shocked even health officials. However, she noted the jump is more likely tied to changes in reporting methods and diagnostic practices than to an increase in infected ticks.
“First of all, the data collection system changed. Since last year, we’ve been receiving disease registration data directly from an electronic system,” Žygutienė said. “Previously, not all Lyme disease cases were reported to us by health care providers.”
Another factor is the ease – and in some cases, carelessness – with which Lyme disease is diagnosed, she added. People often get tested in private labs and, after receiving a positive result, call their doctor, who may prescribe antibiotics and log the case into the system. However, she cautioned that positive antibody tests can persist for up to a year after infection and do not necessarily mean someone is currently ill.
“Antibodies mean that Borrelia bacteria entered your bloodstream, but it doesn’t always mean you are sick or will become sick,” she said.
Žygutienė emphasised that NVSC’s recent research shows no increase in the tick population carrying the Lyme-causing bacteria.
“There have always been a lot of them – about one-third of ticks are infected. But that figure varies by region and forest,” she explained.
Tick season now year-round
The entomologist also noted a rise in tick-borne encephalitis cases, which increased to 807 in 2023 from 589 the year before. Eleven people died from the disease last year. So far this year, 10 cases have already been recorded – an unusual development for the winter months.
“This is the first season where ticks were active all year,” Žygutienė said.
It’s possible to be bitten in the winter. “Most people don’t even consider the risk when heading into the forest to pick a Christmas tree.”
Climate conditions in Lithuania are becoming increasingly favourable for tick activity, she said, adding that people need to adapt accordingly.
No vaccine for Lyme disease, but early removal of ticks is key
Unlike tick-borne encephalitis, there is no vaccine for Lyme disease, and previous infection does not confer immunity. A person can be reinfected multiple times.
The good news is that no Lyme-related deaths were reported last year. According to Žygutienė, early detection and removal of ticks can prevent infection.
“With encephalitis, the virus enters the body almost immediately after the tick bites and releases its saliva into the wound,” she said. “But with Lyme disease, you can still avoid infection if the tick is removed within 24 hours – sometimes even later – because Borrelia bacteria reside in the tick’s midgut and take time to migrate into the bloodstream.”
She also warned that all stages of ticks – larvae, nymphs, and adults – can transmit Lyme disease. The smallest, about the size of a poppy seed, are especially difficult to spot and remove.
Preventive measures still the best defence
Žygutienė debunked the common belief that Lyme disease always causes a red rash or “bull’s-eye” pattern around the bite.
“Not necessarily,” she said. “There are different Borrelia strains, and some don’t cause any skin symptoms at all.”
To reduce the risk of tick bites, she recommended using repellents and wearing protective clothing: long sleeves, pants tucked into socks or boots, and a tightly fitted hat or scarf.
Those with symptomatic Lyme disease are typically treated effectively with antibiotics, except in cases of late-stage illness.
Newsletter
Every Friday morning.
