Abstract
Crimean-Congo haemorrhagic fever (CCHF) is an emerging tick-borne human
disease in Spain. Understanding the spatiotemporal dynamics and exposure
risk determinants of CCHF virus (CCHFV) in animal models is essential to
predict the time and areas of highest transmission risk. With this goal,
we designed a longitudinal survey in two wild ungulate species, the red
deer ( Cervus elaphus) and the Eurasian wild boar ( Sus
scrofa), in Doñana National Park, a protected Mediterranean
biodiversity hotspot with high ungulate and CCHFV vector abundance, and
which is also one of the main stopover sites for migratory birds between
Africa and western Europe. Both ungulates are hosts to the main CCHFV
vector in Spain, Hyalomma lusitanicum. We sampled wild ungulates
annually from 2005 to 2020 and analysed the frequency of exposure to
CCHFV by a double-antigen ELISA. The annual exposure risk was modelled
as a function of environmental traits in an approach to understand
exposure risk determinants that allow us to predict the most likely
places and years for CCHFV transmission. The main findings show that
H. lusitanicum abundance is a major driver of the fine-scale
spatial CCHFV transmission risk, while inter-annual variations in the
risk are conditioned by virus/vector hosts, by host community structure
and by weather variations. The most relevant conclusion of the study is
that the emergence of CCHF in Spain might have been associated with
recent wild ungulate population changes promoting higher vector
abundance. Decreasing wild ungulate population densities could reduce
vector abundance and thus virus prevalence and the risk of CCHFV
transmission to humans.