Stopping TBE: tick research

2018 was a record year for ticks - and the viral diseases they carry. Scientists are studying the possible consequences

If Gerhard Dobler, senior medical officer and virologist at the Bundeswehr Institute for Microbiology in Munich, wants to explain his research object in more detail, he sometimes needs a good microscope. When magnified two hundred times, a tick looks pretty impressive.

Dobler points to the mouthparts and the proboscis on the screen. "Do you see them? Ticks can't bite, they bite." And another misunderstanding quickly clears up: namely, that you should twist ticks out of your skin when they have sucked on for a meal of blood. "Ticks have no threads."

Rather low risk of infection with a single bite

The common wooden goat and its relatives are of particular interest to Dobler for medical reasons. The microbiologist is researching the early summer meningoencephalitis virus, or TBE for short. A tick bite does not automatically mean infection for humans. Only about every hundredth tick carries the virus - and can pass the pathogen on to its human host.

In around a third of those infected, this leads to symptoms such as flu with fever, headache and body aches. What is primarily feared, however, is the so-called meningoencephalitis, in which the meninges and brain become inflamed. Dobler: "TBE has a different medical meaning than other tick-borne diseases such as Lyme disease."

The infections of the past two years therefore caused a stir. In 2017 the Robert Koch Institute (RKI) registered 485 TBE cases, in 2018 there were even 584. Now a project called "Tick-borne encephalitis in Germany" is to find out more about the virus disease. In addition to the RKI, universities and health authorities, among others, are involved, funded by the Federal Ministry of Research. "Our hope is that we will sensitize people to TBE and have significantly fewer cases of illness," says Dobler, who heads the project.

Low vaccination rates even in risk areas

The fact that education is important can be seen, among other things, from the low vaccination rates. Even in high-risk areas, not even every third student is protected, and it is even less among adults.

Today, TBE is mostly transmitted directly from ticks to humans. The research project aims to provide new insights into what exactly the infection means for those affected. "Although we have figures on the infections discovered, we know relatively little about the course of the disease or the long-term consequences," says Teresa Kreusch from the Department of Infection Epidemiology at the RKI.

Tick ​​hunting in Bavaria

To change that, one wants to interview people suffering from TBE. Perhaps this also shows where infectious ticks strike particularly often. After all, the bloodsuckers are not only lurking in the undergrowth. "You can also get stung in the garden. Perhaps we have so far underestimated such risks," said Kreusch.

For their work, however, the researchers urgently need data: tick data. Dobler started one of the most extensive collections himself ten years ago. He hunts once a month in a small area in eastern Bavaria. Dressed in a full-body protective suit, he pulls a light-colored cloth behind him through the tall grass. "The hungry ticks are stripped off and cling to the fabric," explains veterinarian Dr. Lidia Chitimia-Dobler, who goes looking for ticks with her husband.

The parasites are then examined in the laboratory, viruses are isolated and genetically compared with the more than 150 TBE strains. One of the most species-rich collections of ticks in the world is now stored there. Specimens from Africa, South America, Asia and Europe are sent to Munich by post if other researchers are not entirely sure how to identify them.

Mild weather favors the survival of ticks from the tropics

In addition to the wood tick, 18 other tick species are native to Germany. In recent years, however, Chitimia-Dobler has also discovered species that are rather new in this country, for example Ixodes inopinatus, previously only known from Spain, Portugal or Southeastern Europe. "We neither know how widespread this species is in Germany, nor whether it can also transmit new diseases," explains the tick expert.

The tropical ticks Hyalomma marginatum and Hyalomma rufipes come from even more distant regions. Attentive animal owners on horses and a sheep discovered 18 of them and sent them to the institute for identification in 2018. These large ticks were imported by migratory birds before, but did not survive. Now there are increasing indications that the stowaways could settle down thanks to favorable weather conditions. Another development that needs to be kept in mind, says Dobler.

Researchers knew very early on that 2018 would be a tick record year. Together with scientists from the University of Veterinary Medicine, Vienna, a special forecast model was developed. Data that is important for the tick population was incorporated here: temperature data, for example, but also figures on the amount of beechnuts in recent years. "More beechnuts lead to more rodents - and they are the preferred host animals for young ticks," explains meteorologist Dr. Katharina Brugger.

Meaningful forecasts

The model's predictions were pretty accurate straight away. For 2018, it predicted 443 ticks per 100 square meters. The number was almost exactly the same as what the researchers found in their collections. In the future, the model will also estimate the probability of a TBE infection for different regions - similar to a weather forecast. "But we still lack smaller-scale data for this," says Brugger.

It is quite possible that the prognoses have already made some people think. As figures from pharmacies on vaccines showed, almost 20 percent more people in Germany were vaccinated against TBE in 2018 than in the previous year.