Crimean-Congo Hemorrhagic Fever virus detected in ticks in the South of France
In France, scientists from CIRAD (Centre for international cooperation in agricultural research for development) reported the detection of the Crimean-Congo Hemorrhagic Fever (CCHF) virus in ticks of the Hyalomma marginatum species collected in the Eastern Pyrenees (Occitanie). This is the first detection of this virus in France.
No human cases have been detected there.
Since 2015, CIRAD, as part of an agreement with the DGAL, has been studying and monitoring the Hyalomma marginatum tick, one of the proven vectors of the CCHF virus. The studies focus in particular on its distribution area, its history of invasion in France, its seasonal dynamics, its hosts, its carriage of infectious agents. The objective is to assess the risks associated with this vector and the diseases it is likely to transmit.
Every year, in the spring, tick collections are carried out in equestrian structures and cattle farms. This year for the first time, around a hundred ticks out of more than 2000, collected in 2022 and especially 2023 in the spring, tested positive for the presence of the FHCC virus. These results were confirmed in October by the CNR of Viral Hemorrhagic Fevers (VHF) of the Pasteur Institute.
The Hyalomma marginatum tick is a relatively large hard tick (8 mm), recognizable by its long rostrum and its two-colored legs (whitish rings at the joints). It is found in the scrubland or certain pastures of the Mediterranean coast, from the Spanish border to the Var, to Ardèche and the Drôme. Its adult form bites domestic and wild ungulates (cattle, horses, wild boars, and to a lesser extent small ruminants or deer) without danger for them since, even infected with the CCHF virus, the latter do not develop symptoms. In addition, this adult form can occasionally bite humans. It is only active in spring, between April and July.
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“Our collections showed that the tick was distributed throughout the Mediterranean, in rather dry open natural habitats such as scrubland or maquis. According to future climate models, the Mediterranean climate is likely to expand, particularly in the Rhône valley, and on the Atlantic coast to the west, it is likely that the range of this species will expand”, estimates Laurence Vial, veterinary acarologist at CIRAD, and specialist in ticks.
Crimean-Congo hemorrhagic fever is a widespread disease caused by a tick-borne virus (Nairovirus) of the Bunyaviridae family. The CCHF virus causes severe viral hemorrhagic fever outbreaks, with a case fatality rate of 10–40%.
Animals become infected by the bite of infected ticks and the virus remains in their bloodstream for about one week after infection, allowing the tick-animal-tick cycle to continue when another tick bites. Although a number of tick genera are capable of becoming infected with CCHF virus, ticks of the genus Hyalomma are the principal vector.
The CCHF virus is transmitted to people either by tick bites or through contact with infected animal blood or tissues during and immediately after slaughter. The majority of cases have occurred in people involved in the livestock industry, such as agricultural workers, slaughterhouse workers and veterinarians. Human-to-human transmission is possible.
The virus is widespread in some countries of Africa and Asia, in the Balkans, the Middle East and in the south of the European part of Russia.