Tiger mosquitoes, including larvae and pupae, have been found in several places in recent weeks. The dangerous mosquito, which spreads tropical fevers, is gradually establishing itself in our country.
At the beginning of August, someone in his garden in Lebbeke, East Flanders, found a mosquito that looked suspiciously like a tiger mosquito: quite small and dark with white stripes on body and limbs. He posted a photo of the animal on the website www.muggensurveillance.be. This is a ‘citizens platform for monitoring and reporting on the tiger mosquito in Belgium’, which was set up by the Institute of Tropical Medicine (ITM) and the federal public health institute Sciensano. After evaluation it turned out to be a tiger mosquito.
On August 18, researchers from the ITM went on site and investigated the situation within a radius of 500 meters around the site. They found ‘large numbers’ of the mosquito, both larvae and pupae and adult males and females. It is the first time that there is talk of a possible ‘establishment’ of the species in our country. The animals at the base of the population were probably brought in a wagon from Italy in July, where the tiger mosquito is already well established.
Over the past few weeks, confirmed observations have also been made from the Antwerp area via the same site: from Antwerp City, from a tire company in Kallo and from Wilrijk – larvae and pupae were also found at the last location at the beginning of September. Reports came from Grimbergen in the Brussels periphery, Wondelgem near Ghent and Kotem in the Meuse valley. More sightings of the mosquito are already being made in Wallonia, mainly through active monitoring with mosquito traps on car parks along the motorways from the south.
Analysts find it disturbing that so many Flemish observations are made by citizens. ITM’s ‘active’ surveillance picks up fewer mosquitoes. She mainly focuses on places with a higher risk of the introduction of tiger mosquitoes, such as tire centers and garden centers. Tiger mosquitoes are easily spread via eggs in small amounts of water, which remain in car tires and flower pots, mainly containing ornamental bamboo plants.
Embargo for press and public
It is striking that there is little commotion about the recent finds. After each find, involved experts receive a message with the message ‘CONFIDENTIAL: embargo for the press & the general public’. However, it is advisable to map the occurrence of the Asian tiger mosquito as completely as possible, because it spreads tropical viruses that cause fevers such as dengue, west nile, zika and chikungunya. New insights suggest she also transmits yellow fever. Like our local mosquitoes, female tiger mosquitoes need blood to develop their eggs. This allows them to suck in viruses and transfer them to other victims.
Dengue fever has already been observed in Croatia, France, Italy and Spain – it is said to have caused six deaths in Europe so far this year. As of the end of August, 442 cases of West Nile virus have been identified in Eastern and Southern Europe, resulting in at least 20 deaths, mainly in Italy and Greece. Chikungunya and Zika also arrived in Europe and were picked up in the south of France, among other places. So it is no longer just the mosquitoes, but also the viruses that are heading our way.
Mosquitoes are benefiting from globalization, which moves people and goods around the world, and from global warming, which makes conditions more suitable for their survival. Their ideal life temperature is between 20 and 25 degrees Celsius, and if it doesn’t get colder than 3 degrees in winter, they stay alive.
Employees of the Flemish Institute for Technological Research (VITO) mapped out the expected distribution of the tiger mosquito in Europe, in circumstances that were described as ‘business as usual’: no substantial changes in the fight against both global warming and the mosquito. The results were sobering, especially for our region: by the end of the century large parts of Belgium, the Netherlands and northern France will be ideal for tiger mosquito survival. Currently, the populations closest to us are located in the vicinity of the French cities of Paris and Strasbourg.
Flemish experts express great concern about the situation, especially as the seriousness of it does not seem to reach the authorities. Ten years ago, an inter-cabinet working group was urged on monitoring and control, under the motto: every year that we can stop the tiger mosquito means a gain for public health. A monitoring program has been started, which is being carried out by ITM.
The intention was that the monitoring would be taken over after about four years by a new institute that had to step up the fight against the dangerous mosquitoes, following the model of the Dutch Center for Active Monitoring of Vectors. But that never happened. The monitoring by the ITM has been extended each time, but it is too limited to be able to follow up all tiger mosquito populations. The laxity is partly a result of the complexity of our state structures, with competences divided between the federal and regional levels. Nobody really pulls the cart.
Read more below the illustration.
Empty bottle caps
Dutch mosquito fighters express their dissatisfaction with the Belgian approach indoors, because if the mosquito gains a foothold in our home, the chance of a spillover to them increases. Whenever a tiger mosquito is found in the Netherlands, major resources are rolled out to comb the entire neighborhood around the find and inform residents about what they can do to liquidate mosquitoes. This mainly concerns keeping out water puddles in the house and garden, such as in gutters and flower pots. Even empty bottle caps can hold enough water for the mosquito to reproduce.
With us, the available resources are too limited to perform such actions consistently for all finds. There are even too few resources to carry out active monitoring intensively enough. However, the cost of efficient monitoring is minimal compared to what it will cost public health if the tiger mosquito definitively establishes itself in our region.
In addition, the mosquitoes are monitored, but it is not checked whether they are carriers of disease-causing viruses. The chance of that is small, but not zero. For example, in the last two years, four people have been affected by malaria near Zaventem airport, caused by a single-celled parasite that is also transmitted by mosquitoes. Two victims did not survive. It concerned people who had not traveled and were therefore probably infected by a mosquito that had hitch a ride on an airplane.
A recent report in the journal Nature Climate Change came to the conclusion that no less than 58 percent of infectious diseases worldwide are increasing as a result of climate change. The number of cases of dengue fever has increased threefold in half a century. So warnings about tiger mosquito expansion are not counterproductive panic messages. They show the harsh reality.