Possible emergence of Crimean-Congo haemorrhagic fever in France
Ticks of the genus Hyalomma, which have been observed in the south of France for several years, could potentially spread throughout metropolitan France as a result of climate change. These ticks can transmit Crimean-Congo haemorrhagic fever (CCHF), among other diseases. No indigenous cases have been detected in humans in France, but cases are recorded every year in Spain. In its scientific expert appraisal, ANSES confirms the risk of emergence and calls for the nationwide surveillance of these ticks.
Ticks that carry the Crimean-Congo haemorrhagic fever virus
Native to Africa and Asia and introduced mainly by migratory birds from Africa, Hyalomma ticks have been present in Corsica for several decades and along the Mediterranean coast since 2015. Three species of ticks in the genus Hyalomma have been found in France.
These ticks act as vectors for numerous pathogens. In particular, they transmit the parasite responsible for equine piroplasmosis and the Crimean-Congo haemorrhagic fever (CCHF) virus. In humans, Crimean-Congo fever is generally limited to a flu-like illness with digestive problems. In some cases, however, it can worsen and lead to a haemorrhagic syndrome, with a mortality rate of up to 30% in some countries.
Climate change is causing these ticks to spread
Although Hyalomma ticks are present in certain regions of metropolitan France, no human cases of contamination by the CCHF virus have been observed in the country to date. However, around 10 indigenous human cases of CCHF have been reported in Spain since 2013, some of which resulted in the death of the patient. Moreover, in France, antibodies specific to the CCHF virus have been found in domestic and wild animals, suggesting that these animals were exposed on French soil.
Although no human cases have yet been detected, there is a possible risk of CCHF emerging in France. This emergence is made all the more likely by the fact that the geographical area in which these ticks are established is expected to expand due to the ongoing climate change. This is because Hyalomma ticks like dry climates and warm periods. That is why, in France, they are more likely to be found in the maquis and garrigue scrublands around the Mediterranean basin, unlike other ticks, which tend to be found in forests.
Organising the nationwide surveillance of these ticks
ANSES is calling for the implementation of a nationwide surveillance scheme for ticks of the genus Hyalomma as part of vector control measures. This scheme should prioritise the following:
- the geographical areas identified as being the most at risk,
- the development of tools to detect early on the presence of Hyalomma ticks and the circulation of the pathogens they transmit, in particular the CCHF virus and parasites such as Theileria.
The aim of this surveillance is to be able to adopt risk prevention and management measures as the situation evolves, including awareness-raising for healthcare professionals who may be required to identify indigenous human cases.
“Unlike for mosquitoes, there is no national surveillance scheme for ticks, even though they transmit serious diseases such as CCHF, Lyme disease, and tick-borne encephalitis. To best prepare for the potential emergence of the CCHF virus on French soil, it is essential to step up the surveillance of the ticks already in France and those arriving from countries where the virus is currently circulating. These introductions can occur when a Hyalomma tick is attached to a migratory bird, or to an imported horse or cow, for example” adds Elsa Quillery.
Such surveillance should be based on participatory science initiatives such as the CiTIQUE programme, which was created as part of the plan to control tick-borne diseases and could be extended to include Hyalomma ticks.
Developing research into Hyalomma ticks and the CCHF virus
The Agency also stresses the need to launch research programmes to better understand the factors that influence the epidemiology and spatio-temporal dynamics of Hyalomma ticks and the CCHF virus. New knowledge is also needed in order to identify new antiviral compounds for this virus and develop a vaccine.
How can tick bites be prevented?
Hyalomma and Ixodes ricinus (the vector of Lyme disease) tick bites and the diseases they transmit can be prevented by taking the following steps:
- when walking in the countryside, wear closed shoes, avoid exposed skin and wear light-coloured clothing (to more easily spot ticks on the surface of the fabric),
- avoid walking through long grass, bushes and low branches and keep to signposted paths,
- if necessary, use skin repellents with marketing authorisation (MA), but make sure you follow the recommendations for use,
- when you return from a walk in woodlands, macquis or garrigue scrubland or even from your own garden, check your skin – especially the folds – and your scalp for ticks,
- if you are bitten, remove the attached ticks immediately using a tick remover, fine tweezers or, failing that, your nails, and then disinfect the wound,
- monitor the bite area for several days and see your doctor if symptoms (redness, fever, etc.) develop.