Description
In Europe, ticks are the main arthropod vectors of pathogens for humans and domestic animals, and represent an increasingly important problem for public and animal health. Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly important virus transmitted to humans mainly by the bite of infected ticks, and which causes disease in humans with a case-fatality rate up to 30%. It is widespread in many countries of Southeast Asia, Middle East, Eastern and Western Europe. The disease is asymptomatic in the animal reservoir and can therefore expose people in contact with animals or ticks to a higher risk of infection. Human interaction with ecosystems and animals, as well as the sensitivity of ticks and wildlife to environmental and socio-economic changes, can lead to an increase in the disease burden associated with tick-borne diseases. In Corsica, several factors are present, such as climatic change, the presence of the main tick vector Hyalomma, and the interaction between livestock, wild animals and humans encouraged by mass tourism and extensive agriculture. A One health approach studying the virus in its 3 different compartments is essential to strengthen preparedness for the emergence of CCHFV in Corsica. The aim of our study is to determine the risk of CCHFV infection by investigating the presence of CCHFV in ticks and its seroprevalence in blood samples from the human and animal population.
Firstly, a total of 5,165 ticks were collected from 465 cattle in Corsica’s main slaughterhouses during 2022-2023. Ticks were pooled and screened for the presence of CCHF virus genome based on L segment using RT-qPCR method. 24 CCHFV-positive pools (119 ticks) from 3 regions (southern Corsica) were identified. After sequencing and phylogenetic analyses, partial sequences for S, M and L have been obtained. Two genetic lineages were identified: Africa 1 for S and M segments and Africa 3 for L segment. Additional sequencing is currently ongoing to obtain the complete S fragment, which will enable us to determine a hypothesis about the origin of the Corsican virus in relation to that of Spain.
Secondly, a human seroprevalence study was set up, involving 201 at-risk participants (livestock farmers, slaughterhouse workers, veterinarians and field staff) and 2472 participants from the general population. In the at-risk population, a questionnaire was carried out along with the blood collection in order to investigate risk factors associated with these populations. After blood analysis using enzyme-linked immunosorbent assay (ELISA), the results highlighted the detection of anti-CCHFV in a slaughterhouse worker who had already been bitten by ticks in Corsica and had developed symptoms following tick bite. In addition, serum samples from 211 cattle slaughtered in Cuttoli (Southern region) were tested by ELISA and 4 (1.9%) were found to be positive for CCHFV.
Results showed the possible well- established circulation of CCHFV in Corsica. Further research is needed to better define risk of CCHF disease. Prevention programs and livestock monitoring to reduce the dispersion of ticks are recommended before this virus became endemic in Corsica and further spread to Western Europe.
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