You may have heard about the book Spillover by David Quammen. In a nutshell, this fascinating book describes how diseases can emerge from animals and spread to humans. An entire chapter is dedicated to the story of Lyme disease, a disease caused by a bacterium. Lyme disease affects approximately 65,000 people in Europe and can give rise to long term consequences including fatigue, pain and memory problems. The name comes from the city of Lyme in the US where the disease was first characterized.
There may be no apparent reason to talk about Lyme disease on a website dedicated to flaviviruses. Except that there is one: ticks. Borrelia burgdorferi, the bacterium causing Lyme disease, infects humans trough ticks. A tick may bite a human in search of a fresh meal of blood but if it is infected, while feeding it leaves the bacterium to pass into human blood, where it stays giving rise to the first symptom: a red rash at the site of infection.
Unfortunately, Lyme disease is not the only tick-borne disease. Like Borrelia burgdorferi a number of other bacteria and viruses can be carried by ticks and some are severe human pathogens. One of these is tick-borne encephalitis virus, TBEV, that causes the tick-borne encephalitis. It belongs to flaviviruses a family of viruses that takes its name from its most notorious member: the virus that causes yellow fever. However, many flaviviruses find their vector in ticks between hosts and thereby they also reach humans. These viruses are the research subject of the TBFVnet project.
TBFVnet stands for Tick-borne flavivirus network. Researchers from six different institutes across as many countries in Europe work together to study and survey flaviviruses carried by ticks. Beside TBEV, the project focuses its efforts on three other tick-borne flaviviruses that affect the human population: the Powassan virus (POWV), the Louping-ill virus (LIV) and the Omsk hemorrhagic fever virus (OHFV). In 2019 in Europe there were 3246 confirmed cases of TBE alone (with an incidence of seven per million of habitants) marking an increase over the past years as reported by the European Centre for Disease Prevention and Control (ECDC) dedicated page. At the moment a vaccine is available only for TBE, while for other tick flaviviruses there is no vaccine or specific treatment. The TBFV network aims to fill this gap sharing expertise to understand their biology, develop treatments and diagnostic tools.
The problem with tick-borne diseases is the tick itself. They are quite difficult to see, and they can bite anyone engaged in outdoor activities such as hiking or farming. Unfortunately, it is difficult to sense a tick bite, most of the time you could notice the tick on your skin just when you are back home. However, and here comes the first good news, even if ticks can be anywhere outdoors, the pathogens are not. Viruses carried by ticks have their own geographical distribution that is monitored and visible through local authorities and on the ECDC website. Surveillance data are important to understand the distribution of a pathogen and to establish risk areas and implement countermeasures. However, monitoring capacity is unevenly distributed in different countries and TBFVnet aim at filling this gap.
More good news follows at the end of this story. First, in a given area just a small fraction of ticks carry the pathogen. So, the probability of being infected is low. The second is even more important because it is something each of us can do: protect ourselves. This is very easy, because the moment we are aware of this threat we can do something. On the EDCD website there is a section listing personal actions to protect ourselves. For example, we can check whether there are any known tick-borne diseases in the area we are planning our outdoors activities. Even more easily, we can wear suitable clothing: long trousers and long-sleeved shirts can easily protect our skin from ticks. For those who want to feel even safer, there are also insect repellants that can be applied on boots or clothes to raise the level of protection.
In Norway they say, “There is no bad weather, only inappropriate clothing”. At the end of this story, we can borrow this saying and remember that there will be no detrimental tick bites if we prepare.
