First national map of risk of infection with Crimean-Congo hemorrhagic fever virus

    An epidemiological model based on deer makes it possible to draw up the first risk map of exposure to the Crimean-Congo hemorrhagic fever virus in Spain and will be key to preventing the disease in people


    Crimean-Congo hemorrhagic fever virus (CCVF) is a orthonairovirus of African origin transmitted by ticks that is endemic in Africa, the Middle East, Asia and southeastern Europe, but also in the Iberian Peninsula. The virus only causes illness in people, and although only 1-2 people out of 10 who become infected may present any symptoms, the occurrence of severe and fatal cases is rare, the World Health Organization (WHO) includes FHCC on its list of top emerging infectious diseases and considers it a priority disease with pandemic potential due to the severe hemorrhagic picture that it can cause (similar to Ebola) and because it is transmissible between people.

    Although this virus only causes illness in people, It is maintained by animals and ticks, so some wildlife species, such as deer (Cervus elaphus), act as reservoirs of the virus. In 2010 the virus was detected in Spanish ticks of the species Hyalomma lusitanicum, and in 2016 the first fatal case from a tick bite was reported in the south of Ávila, as well as the contagion, through this patient, of a nurse who recovered from the disease. Up to 2021, 10 human cases have been reported in Spain, several of them fatal, so Crimean-Congo hemorrhagic fever is currently considered an emerging human disease in Spain.

     

    Although this virus only causes disease in people, it is maintained by animals and ticks, so some wildlife species, such as deer (Cervus elaphus) act as reservoirs of the virus.

    Because there is no treatment or vaccine that protects people against this disease, prevention is the main tool to fight against its spread, so it is essential to know where there is the greatest risk of becoming infected with the VFHCC. However, until now, there was no risk map for Crimean-Congo hemorrhagic fever virus infection in Spain.

    Scientists from the Research Group in Health and Biotechnology (SaBio) of the Institute for Research in Hunting Resources (IREC – CSIC, UCLM, JCCM), in collaboration with a multidisciplinary team of international researchers, have analyzed the degree of exposure of Iberian deer populations to VFHCC. This wild ungulate is the main host for ticks of the genus hyaloma in Spain, so the scientists considered assessing whether it could be a good model to identify risk determinants and capture them on a map that would serve to inform public health authorities and the public.

     

    Spatial location of the deer populations sampled (red dots) and size of the local sample in relation to the distribution of deer (blue shaded squares) in the Iberian Peninsula.

    The results of this work, recently published in the journal Transboundary and Emerging Diseases, show that 61% of deer populations and 88% of sampled animals were positive for the virus. The greatest exposure to VFHCC was observed in the southwest of the Iberian Peninsula, precisely where Hyalomma lusitanicum It is more abundant in Spain due to the climate and the abundance of wild ungulates. In fact, eight of the nine primary cases of VFHCC registered in Spain occurred in or near these areas of greatest risk, that is, where the highest prevalence of infection by the virus in ticks is observed, which demonstrates that the deer-based model accurately anticipates risk to the human population.

     

    Predictive map of the risk of exposure to the Crimean-Congo hemorrhagic fever virus (CCVF) in Spain obtained from the results in deer. On the map, the strongest color indicates the highest risk. The nine primary human cases of FHCC reported in Spain, up to June 2021, are shown on the map as stars.

    This study will make it possible to deepen the analysis of the spatiotemporal risk of the transmission of HCCV to animals and people, allowing predict the evolution of this zoonotic disease and the occurrence of severe cases in people.

    The scientific publication of this research is available at:

    • Cuadrado-Matías, R., Cardoso, B., Sas, MA, García-Bocanegra, I., Schuster, I., González-Barrio, D., Reiche, S., Mertens, M., Cano-Terriza, D. ., Casades-Martí, L., Jiménez-Ruiz, S., Martínez-Guijosa, J., Fierro, Y., Gómez-Guillamón, F., Gortázar, C., Acevedo, P., Groschup MH, Ruiz- Fons, F. 2021. Red deer reveal spatial risks of Crimean-Congo haemorrhagic fever virus infection. Transboundary and Emerging Diseases