The Crimean-Congo haemorrhagic fever tick vector Hyalomma marginatum in
south of France: Modelling its distribution and determination of factors
influencing its establishment in a newly invaded area
Abstract
For the first time we built a correlative model for predicting the
distribution of H. marginatum, one of the main vector of Crimean-Congo
Haemorrhagic fever virus (CCHFV), at high resolution in a recently
colonized area, namely south of France. Field tick collections were
conducted on horses from 2016 to 2021 in 14 French southern departments,
which resulted in a first map of H. marginatum on 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 the tick abundance, were correlated to multiple parameters that
described the climate and habitats characterizing each collection site,
as well as movements of horses as a possible source of tick diffusion
and new establishment. Our model highlighted the importance of warm
temperatures all along the year, as well as dry conditions during summer
and moderate annual humidity for the establishment of H. marginatum. A
predominance of open natural habitats in the environment was also
identified as a supporting factor, in opposition to artificial and humid
habitats that were determined as unsuitable. Based on this model, we
predicted the current suitable areas for the establishment of the tick
H. marginatum in South of France, with a relatively good accuracy using
internal and external validation methods. Concerning tick abundance,
some correlative relationships were similar than in the occurrence model
but the type of horse movements were also pointed out as an important
factor explaining the mean parasitic load, leading to differential
exposure to ticks. The limitations of estimating and modelling H.
marginatum abundance in a correlative model are discussed.