Almost ten years after the first report in Occitania, Hyalomma Marginatum, the “striped” tick, also called the “giant tick,” has established itself in the region. Scientists from CIRAD and IRAE tracked it on farms for several weeks to measure the phenomenon. Following reports of parasites carrying the Crimean-Congo hemorrhagic fever virus in the Eastern Pyrenees last year, the disease, which is endemic in Africa, Asia and the Middle East, may appear in France, according to new data.
It is large (8 mm), armed with a spur, a “rostrum” for the scientists studying it, has two-colored legs decorated with whitish rings on the joints, and lives in bushes on the Mediterranean coast. Montpellier researchers are on her trail. Last October, for the first time in France, the Crimean-Congo hemorrhagic fever (CCHF) virus was detected in specimens of Hyalomma Marginatum, the “striped tick.” Ticks were collected from cows and horses in the Eastern Pyrenees.
Although there have been no documented cases of transmission of the virus to humans, this Ebola-like disease is potentially serious.
Within a few weeks, scientists from Cirad and Inrae and the University of Montpellier have returned to the area: they are looking for Hyalomma marginatum, as well as Ixodes ricinus, another tick species quite common in the north and west of the region, which transmits Lyme disease. , “we find it neither in Hérault, nor in Gard, nor in Aude, nor in the Eastern Pyrenees”– elaborates Thierry Pollet, an epidemiologist researcher attached to Inrae, associated with Cirad and the mixed research unit ASTRE of the University of Montpellier in the collective “Vectors”, from his laboratory at the Bayarguet campus, north of Montpellier.
On the other hand, teams are tracking Dermacentor marginatus, a carrier of animal diseases, particularly equine piroplasmosis, which debilitates and sometimes kills infected animals.
“Ticks collected from horse and cattle breeders are being analyzed”, the scientist points out. Spring is the most favorable time of year for observations: “This is where the ticks become active, with missions continuing into July and August.”
“We talk a lot about mosquitoes, but ticks are also a public health problem.”
Will the samples confirm CCHF virus circulation in France? The evolution of the tick population observed since 2015 by the CIRAD team in Montpellier is alarming: “This poses a serious threat to the health of both people and animals.“, the research institute points out.
In addition to Lyme borreliosis, the most famous tick-borne disease, reported by 8 out of 10 French people, which affected 47,000 people in France in 2021, according to Public Health France.
“Hunting” tick
Ticks develop in three phases: from larvae to nymphs and adults. After feeding on blood, a tick can increase its weight up to 100, regardless of the species: Ixodes ricinus, Hyalomma Marginatum, Dermacentor Marginatus… and the classic dog tick Rhipicephalus sanguineus.
To find a host, the parasite uses several strategies. Ixodes ricinus, explains Thierry Pollet, “is on alert, on a branch of grass. A hunter, he is sensitive to changes in CO2 and earth vibration. He is always ready and runs to attach himself to his owner.”
To remain undetected, the tick spits out, pumping blood, saliva filled with anesthetics and anticoagulants. It is in this saliva that pathogens are present that are transmitted to the host.
On the scale of Occitania, and even more so in the future with climate change, the risk of CCHF cases among people in France is especially alarming. The “striped-legged” tick, unlike Ixodes ricinus, is found mainly in forests, where it finds favorable humidity, “loves the dry Mediterranean climate and bushland.”
“We talk a lot about mosquitoes, but on a European scale ticks are also a medium-term public health problem.”, points out Thierry Pollet. In Spain, the first reports of human transmission of the virus were recorded in 2016. “two or three cases a year.”
In France it is “a whole network of actors” which is mobilized, on the front line are breeders, as well as environmental associations, tourists…
“We shouldn’t panic”
Harmless to animals (the horses and cattle it infests do not show symptoms), Ixodes ricinus can cause more or less serious cases of infection: “We shouldn’t panic”Thierry Pollet’s nuance.
“In the vast majority of cases, nothing happens. Lyme borreliosis is present in only 10–15% of Ixodes ricinus.”. AND “Even if a tick carries the bacteria, the risk of transmitting it is only 10%. If we remove it within 24 hours, most likely nothing will happen.”
What if a giant tick transmits the CCHF virus?“it could be nothing at all.” But the most vulnerable people, especially those with weakened immune systems, are at risk.
After a walk “you should always examine yourself”, before “it’s wiser to protect yourself”
How to avoid a tick bite or limit the risk of infection if necessary?
“If you are bitten by Hyalomma marginatum, you have an immediate risk of infection, but in the case of Ixodes ricinus, which transmits Lyme disease, this can be avoided within 24 hours,” the scientist says.
To play it safe, “you should always check yourself” after a walk, mainly “behind the ears, at the base of the neck, between the toes, in the crook of the knees, in the groin, under the arms.” And the examination must be repeated “within 48 hours.”
When you go for a walk, even in summer, “you can’t wear shorts and flip-flops”: “You should wear trousers, high-top shoes and socks that don’t expose your skin or cover your arms.”
It is better to wear “light clothing”, which will also allow you to detect the tick.
The presence of a tick should not cause panic, and Thierry Pollet would not want people to “discourage going into the forest”: “If you notice a tick, you should remove it with a tick remover if you have one, or turn the tick with a gesture unscrewing so that its harpoon does not remain in the body. Only after this the bite site should be disinfected. Then “observe yourself for two to three weeks.” Suspicion of Lyme disease is manifested by erythema migrans, a red spot. CCHF infection causes “flu-like symptoms.” Then you should consult a doctor.
Finally, what to do with the beast? “Instead of crushing it and throwing it away, you should report it to the CITique app,” a collaborative research program to which it can be submitted. This consultation between professionals and citizens also formed the basis of the board game GoTicks, published by the Montpellier company Bioviva.
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