Study: Most city ticks in Estonia carry dangerous pathogens

Castor bean tick
Castor bean tick Source: Erik Karits / Pixabay

A recent ticks study by the Estonian Institute for Health Development (TAI) concludes that the little arachnids can be found in almost every city in Estonia and that 70 percent carry the tick-born encephalitis virus, bacteria that cause Lyme disease or other dangerous human pathogens.

TAI investigators visited parks, disc golf courses and other green areas in 47 Estonian cities this spring and summer. "The criteria included human activity, that the area was within city limits /.../ and that ticks could survive there," said Maria Vikentjeva, research fellow at the communicable diseases department of TAI. This means that well-tended central parks were usually left out of the study.

The results were that the little bloodsuckers can be found everywhere, with green areas in Kilingi-Nõmme and the parks of Haapsalu Castle the only exceptions. "We found the most ticks on the Priimetsa walking paths in Valga. We counted 27 ticks per 100 square meters there," Vikentjeva remarked. In most places, fewer than five ticks per 100 square meters were found.

Vikentjeva said that tick numbers can vary greatly from one city to the next and from one area within the same city to the next. For example, while the Tallinn average came to a little over four ticks per 100 square meters, their abundance in the Open Air Museum was comparable to the walking paths of Valga County.

Ticks love shady and damp places the most. "It came as news to us that they can thrive even in open areas if the grass is tall enough and in the conditions of solid biodiversity," the expert said. This begs the conclusion that refraining from cutting the grass in green areas might help boost tick populations. It would be especially wise to avoid rummaging through bushes.

"But seeing as Tallinn is a green capital of Europe, we cannot really combat biodiversity. Ticks are a part of that diversity. We need to learn to live with them and take care in our actions," the research fellow said.

After their outing to the fields, the researchers looked at how often the ticks they collected carried various pathogens. They examined 1,931 ticks, looking for tick-born encephalitis, Lyme disease, human anaplasmosis, ehrlichiosis, relapsing fevers Borrelia species and rickettsioses pathogens. Based on the results, the prevalence of pathogens in ticks has grown considerably over the last five years.

On average, 69.4 percent of ticks collected tested positive for at least one pathogen, with 39 percent of ticks carrying rickettsioses pathogens and a third bacteria that causes Lyme disease.

The relative importance of so-called toxic ticks was greatest at the Tammiku hiking trail in Rakvere at 84 percent of all specimens collected. Ticks in Pärnu carried pathogens the most seldom at 52 percent.


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Editor: Jaan-Juhan Oidermaa, Marcus Turovski

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