The Crimean‐Congo haemorrhagic fever tick vector Hyalomma marginatum in the south of France: Modelling its distribution and determination of factors influencing its establishment in a newly invaded area

Abstract

We developed a correlative model at high resolution for predicting the distribution of one of the main vectors of Crimean-Congo haemorrhagic fever virus (CCHFV), Hyalomma marginatum, in a recently colonised area, namely southern France. About 931 H. marginatum adult ticks were sampled on horses from 2016 to 2019 and 2021 in 14 southern French departments, which resulted in the first H. marginatum detection map on a large portion of the national territory. Such updated presence/absence data, as well as the mean number of H. marginatum per examined animal (mean parasitic load) as a proxy of tick abundance, were correlated to multiple parameters describing the climate and habitats characterising each collection site, as well as movements of horses as possible factors influencing tick exposure. In southern France, H. marginatum was likely detected in areas characterised by year-long warm temperatures and low precipitation, especially in summer and mostly concentrated in autumn, as well as moderate annual humidity, compared to other sampled areas. It confirms that even in newly invaded areas this tick remains exclusively Mediterranean and cannot expand outside this climatic range. Regarding the environment, a predominance of open natural habitats, such as sclerophyllous vegetated and sparsely vegetated areas, were also identified as a favourable factor, in opposition to urban or peri-urban and humid habitats, such as continuous urban areas and inland marshes, respectively, which were revealed to be unsuitable. Based on this model, we predicted the areas currently suitable for the establishment of the tick H. marginatum in the South of France, with relatively good accuracy using internal (AUC = 0.66) and external validation methods (AUC = 0.76This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Ornithological and molecular evidence of a reproducing Hyalomma rufipes population under continental climate in Europe

“…Recently, the emergence of Hyalomma marginatum was reported in a previously non-endemic region of the Mediterranean Basin in southern France, but it was stated that even in such newly invaded areas this tick species probably remains exclusively Mediterranean and cannot expand outside this climatic range ( 11 ). On the other hand, north of the Mediterranean region, in the Carpathian Basin [geographically including both Hungary and the Transylvanian Basin: ( 12 )], adult ticks from the genus Hyalomma are long-known for their autochthonous occurrence under continental climate.…”

Systematic Review on Crimean–Congo Hemorrhagic Fever Enzootic Cycle and Factors Favoring Virus Transmission: Special Focus on France, an Apparently Free-Disease Area in Europe

“…In the South of France, extensive farming systems where animals are highly exposed to ticks do exist, as observed for cattle rearing in Camargue. However, these areas are of wet habitats and have been demonstrated as unsuitable for the establishment of the H. marginatum tick vector ( 103 ). Extensive farming can also be temporary as mostly reported in Corsica where most cattle are free-ranging in suitable scrubs during spring and summer, corresponding to the activity period of the adult stages of H. marginatum .…”

“…In relation to global warming, habitats can also change and become more or less suitable for both the survival of CCHFV tick vectors and the increased abundance of some wild mammal species, such as wild boars ( 113 ). In southern Europe, including the South of France, specific categories of xerophilous land covers such as shrubs, grasslands, and herbaceous vegetation may expand under climate change and favor the establishment of H. marginatum ( 103 ) among locally abundant small vertebrates population such as hares and rabbits ( 74 ). In addition, modifications in land use and husbandry practices, as a consequence of either climate or global changes (e.g., land conversion to pastures through deforestation), can contribute to an increase of open areas.…”

Ornithological and molecular evidence of a reproducingHyalomma rufipespopulation under continental climate in Europe

“…Recently, the emergence of Hyalomma marginatum was reported in a previously non-endemic region of the Mediterranean Basin in southern France, but it was stated that even in such newly invaded areas this tick species probably remains exclusively Mediterranean and cannot expand outside this climatic range [10]. On the other hand, north of the Mediterranean region, in the Carpathian Basin (geographically including both Hungary and the Transylvanian Basin: [11]), adult ticks from the genus Hyalomma are long-known for their autochthonous occurrence under continental climate.…”