As part of a study aimed at detecting its presence in France, CIRAD (Center for International Cooperation in Agricultural Research for Development) has detected the Crimean-Congo Hemorrhagic Fever (CCHF) virus in ticks of the species Hyalomma marginatum collected from cattle in the Pyrénées-Orientales. These initial analyses were confirmed by the CNR (National Reference Center for Viral Hemorrhagic Fevers) at the Pasteur Institute, thereby establishing for the first time the presence of the virus in France. Santé publique France provides an update on the risks to the public and reiterates recommendations for preventing tick bites intended for livestock farmers, farmers, hikers, and anyone likely to frequent areas (such as pastures and scrubland) where these ticks are found along the Mediterranean coast.

What are the potential risks to the public?

Santé publique France has analyzed the situation in collaboration with its partners at ANSES, CIRAD, and the CNR des FHV using a One Health approach.

In humans, infection with the FHCC virus is most often asymptomatic or paucisymptomatic. However, the virus can cause hemorrhagic fever, which can be severe with a case fatality rate of 5 to 30%.

The virus is generally transmitted through the bite of an infected adult tick of the genus Hyalomma. Transmission to humans is also possible through direct contact with the blood or bodily fluids of an infected animal or human (during the short period when the virus is circulating in the blood).

To date, no indigenous cases (infections acquired within France) have been detected in humans in France.

A more in-depth multidisciplinary assessment of the risk of human cases will be conducted for the next tick season in spring 2024 and in subsequent years.

Where is the Hyalomma marginatum tick found in France?

Native to Africa and Asia and introduced mainly by migratory birds from Africa, the Hyalomma marginatum tick has been present in Corsica for several decades and was detected starting in 2015 by CIRAD along the Mediterranean coast. Currently, there is no active tick surveillance program in France at the national level, regardless of the species. Such surveillance was recommended by ANSES in its May 2023 advisory. Several studies have been or are being conducted to assess the presence in France of these ticks and certain infectious agents they may carry. CIRAD has thus been able to demonstrate that the Hyalomma marginatum tick is present throughout the Mediterranean region and is likely to spread further north in the future due to climate change.

As part of the scientific studies conducted by this research institute, analyses conducted in 2022 and 2023 on Hyalomma marginatum ticks collected from cattle in the Pyrénées-Orientales revealed, for the first time, the presence of genetic material from the FHCC virus, whereas until now it had only been detected indirectly through the presence of antibodies in domestic and wild ungulates. Future investigations will seek to determine whether the virus is circulating more widely across southern France.

The CNR-FHV (National Reference Center for Viral Hemorrhagic Fevers) at the Pasteur Institute has confirmed these results and is currently conducting viral sequencing analyses to understand the origin of the strains found.

What is Crimean-Congo hemorrhagic fever, and what are its symptoms?

CCHF is a disease caused by a virus of the Nairovirus family, whose primary vectors are ticks of the genus Hyalomma. In humans, it is generally limited to flu-like symptoms with digestive issues. In some cases, however, it can worsen and lead to a hemorrhagic syndrome (potentially severe bleeding), with a mortality rate of up to 30% in some countries. Management of CCHF relies primarily on symptomatic treatment in a hospital setting.

Symptoms of Crimean-Congo hemorrhagic fever

Generally, symptoms appear suddenly and mainly include fever, myalgia (muscle pain), digestive issues, dizziness, neck stiffness and pain, back pain, headaches, eye sensitivity, and photophobia (discomfort caused by light). In severe cases, these symptoms may be followed by bleeding, shock, and multi-organ failure.

What should you do if you are bitten by a tick?

If bitten, monitor your overall condition and consult a doctor promptly if symptoms appear within one month of exposure.

How is Crimean-Congo hemorrhagic fever transmitted?

In humans, infection with the CCHF virus occurs through bites from adult ticks of the genus Hyalomma. The Hyalomma marginatum tick is a relatively large hard tick (5 mm), recognizable by its long rostrum and two-toned legs (whitish rings at the joints).

The frequency of bites on humans is believed to be low, as these ticks do not have a particular preference for humans. Furthermore, they are generally more visible than other tick species because they are slightly larger, making it easier to spot them before they bite.

The FHCC virus can also be transmitted through contact with bodily fluids from infected humans or animals that are viremic, noting that these animals remain viremic for only about ten days. There is no airborne transmission. The FHCC virus is an RNA virus that does not survive in the environment. The virus is not transmitted through the consumption of raw milk dairy products, and transmission through the consumption of meat from infected animals has never been reported. In France, the Hyalomma marginatum tick, in its adult form, bites domestic and wild ungulates (cattle, horses, small ruminants, deer) and occasionally humans. It is capable of transmitting the virus through its bite but is active only in the spring between April and July. The risk of transmission through bites from these ticks present in the environment and through the bodily fluids of these animals is therefore seasonal.

Ticks attached to livestock do not pose a bite risk to humans, as they are unable to re-bite after biting the animal^1,2. Furthermore, the immature forms of these ticks (nymphs) feed on small mammals, such as hares, until October and can infect these animals. Therefore, caution is advised when hunters skin these animals (risk associated with contact with bodily fluids).

How can you protect yourself from tick bites?

Since there is no vaccine against TBE, the best way to reduce the risk of infection in humans is to protect yourself against tick bites:

• when walking in nature, wear closed-toe shoes and light-colored, long-sleeved clothing to better spot ticks on the fabric, and tuck your pants into your socks;

• avoid walking through tall grass, bushes, and low-hanging branches, and stick to marked trails;

• if necessary, use skin repellents with marketing authorization (MA), strictly following the usage instructions (2023 recommendations for travelers regarding repellents);

• Check yourself after returning from walks in the forest, scrubland, or garden, paying particular attention to skin folds and the scalp;

• If bitten, immediately remove attached ticks using a tick remover, fine-tipped tweezers, or, if unavailable, your fingernails, and disinfect the area;

• monitor your overall health and consult a doctor promptly if symptoms appear within a month of exposure.