2024-04-28 18:01:00
Almost ten years after a first report in Occitania, Hyalomma marginatum has established itself in the region. Scientists from CIRAD and INRAE have tracked it on farms for several weeks to measure the phenomenon. With new data: Since the report of parasites carrying the Crimean-Congo hemorrhagic fever virus last year in the Pyrénées-Orientales, the disease, endemic in Africa, Asia and the Middle East, may appear in France.
It is large (8 mm), is armed with a spur, a “lectern” for the scientists who study it, is carried by two-colored legs decorated with whitish rings in the joints, lives in scrub on the Mediterranean coast. Montpellier researchers are following her trail. Last October, for the first time in France, the Crimean-Congo hemorrhagic fever (CCHF) virus was detected in samples of Hyalomma marginatum, the “striped-legged tick”. The mites were collected from cows and horses in the Pyrénées-Orientales.
Although no cases of transmission to humans have been documented, the condition, similar to Ebola, is potentially serious.
Hyalomma marginatum, “striped tick”, on the front line. Behind, Ixodes ricinus. MICHAEL ESDOURRUBAILH – MICHAEL ESDOURRUBAILH
For several weeks, researchers from Cirad and Inrae and the University of Montpellier have been back in the field: looking for Hyalomma marginatum, but also Ixodes ricinus, another tick species that is quite present in the north and west of the region, and which transmits Lyme disease. , “we do not find it in the Hérault, nor the Gard, nor the Aude nor the Pyrénées-Orientales”specifies Thierry Pollet, epidemiologist researcher associated with Inrae, associated with Cirad and ASTRE mixed research unit of the University of Montpellier in the “Vectors” collective, from his laboratory at the Baillarguet campus, north of Montpellier.
Ticks are always seen in the same place on the animal: mane, udder, etc. DR MAXIMILIAN BARBIER
On the other hand, the teams track Dermacentor marginatus, a vector of animal diseases, especially piroplasmosis in horses, which exhausts and sometimes kills the infected animal.
“Ticks collected from horse and cattle breeders are analyzed”, the researcher indicates. Spring is the most favorable season for observations: “This is where the tick comes into action, the missions continue until July and August.”
“We talk a lot about mosquitoes, but ticks are also a public health problem”
Will the samples confirm the circulation of the CCHF virus in France? Monitored since 2015 by a CIRAD team in Montpellier, the development of the tick population is worrying: “It poses a serious risk to both human and animal health.“, states the research institute.
Ticks full of blood on a farm inspected in West Occitanie, 22 April. DR MAXIMILIAN BARBIER
Beyond Lyme borreliosis, the most famous tick-borne disease cited by 8 out of 10 French people, which affected 47,000 people in France in 2021 according to Public Health France.
A “hunting” tick
Ticks develop in three stages, from larva to nymph to adult. When the tick is full of blood, it can multiply its weight up to 100, whatever the species: Ixodes ricinus, Hyalomma marginatum, Dermacentor marginatus… and the classic dog tick, Rhipicephalus sanguineus.
To find a host, the parasite has several strategies. Ixodes ricinus, explains Thierry Pollet, “is on the lookout, on a blade of grass. A hunter, it is sensitive to variations in CO2 and vibrations in the ground. It stays ready and runs to attach itself to the host”.
To go unnoticed, the tick spits out, as it pumps blood, saliva filled with anesthetics and anticoagulants. It is in this saliva that the pathogens that are transmitted to the host are present.
On the scale of Occitania, and even more so in the future with climate change, it is above all the risk of human cases of CCHF emerging in France that is worrying. The “striped” tick, unlike Ixodes ricinus, is mainly found in forests where it finds favorable moisture, “likes the dry Mediterranean climate and scrubland”.
Mediterranean vegetation and the increasingly dry climate contribute to the spread of parasitic mites. DR MAXIMILIAN BARBIER
“We talk a lot about mosquitoes, but on a European scale, ticks are also a public health problem in the medium term”, indicates Thierry Pollet. In Spain, the first reports of transmission to humans were documented in 2016. Since then, the country has registered “two or three cases per year”.
In France it is “a whole network of actors” which is mobilized, with breeders in the front line, but also environmental associations, hikers…
“We must not panic”
Harmless to animals (the horses and cattle it colonizes do not show symptoms), Ixodes ricinus can cause more or less severe cases of infection: “We must not panic”shades Thierry Pollet.
Thomas Pollet is co-responsible for the Cirad/Inrae “Vectors” collective. Midi Libre – MICHAEL ESDOURRUBAILH
“In the vast majority of cases, nothing happens from Lyme disease in 10 to 15% of Ixodes ricinus.”. One “Even if the tick carries the bacteria, there is only a 10% chance that it will transmit it. If we remove it within 24 hours, most likely nothing will happen.”
What if the giant tick transmits the CCHF virus?“it may be nothing at all”. But the most vulnerable, and especially the immunocompromised, are at risk.
After a trip, “you always have to inspect yourself”, before “it makes more sense to protect yourself”
How to avoid being bitten by a tick, or limit the risk of infection if necessary?
“If Hyalomma marginatum bites you, you have an immediate risk of infection, but for Ixodes ricinus, which transmits Lyme disease, it is possible to avoid it for 24 hours,” says the researcher.
To avoid taking any risks, “you must always inspect yourself” after an outing, mainly “behind the ears, at the base of the neck, between the toes, by the knees, in the groin, under the armpits”. And the examination must be repeated “for 48 hours”.
When you go for a walk, even in summer, “you must not go in shorts and flip-flops”: “You must wear trousers, high shoes and socks that avoid leaving the skin exposed and cover the arms.”
Instead, wear “light clothes” that allow you to see a tick as well.
The presence of a tick should not cause panic, and Thierry Pollet does not want people to “prevent themselves from entering the forest”: “If you spot one, you should remove it with a tick remover if you have one, or turn the tick off with the gesture of screwing off, to prevent the harpoon from remaining in the body. Then “observe yourself for two to three weeks” is manifested by erythema migrans. infection will cause “flu-like symptoms.” Then you should see a doctor.
Finally, what should I do with the beast? “Instead of crushing it and throwing it away, you should report it on the application CITic“, a participatory research program towards which it can be directed. This consultation between professionals and citizens is also the origin of a board game, “GoTicks” published by the Montpellier company Bioviva.
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