The historical ecological background of West Nile virus in Portugal provides One Health opportunities into the future

Abstract

West Nile (WNV) is a zoonotic arbovirus with an expanding geographical range and epidemic activity in Europe. Not having yet experienced a human-associated epidemic, Portugal remains an outlier in the Mediterranean basin. In this study, we apply ecological niche modelling informed by WNV historical evidence (1969-2022) and a multitude of environmental variables from across Portugal. We identify that ecological backgrounds compatible with WNV historical circulation are mostly restricted to the south, characterized by a warmer and drier climate, high avian diversity, specific avian species and land types. We estimate WNV ecological suitability across the country, identifying overlaps with the distributions of the three relevant hosts (humans, birds, equines) for public and animal health. From this, we propose a category-based spatial framework providing first of a kind valuable insights for future WNV surveillance under the One Health nexus. We also forecast that climate trends alone will contribute to pushing adequate WNV ecological suitability northwards, toward regions with higher human density. This unique perspective on the past, present and future ecology of WNV addresses existing national knowledge gaps, enhances our understanding of the evolving emergence of WNV, and offers opportunities to prepare and respond to the first human-associated epidemic in Portugal.

Serological Evidence of Antibodies to West Nile Virus in Wild Birds in Portugal

“…A previous article reports the results of a serological and virologic survey of birds (and horses) [15] and, more recently, another study reports a serological surveillance study [16] but despite being a notifiable disease in Portugal, WNV surveillance remains passive. Despite evidence of WNV circulation in Portugal since 1969 [17] there has not yet been a WNV human epidemic in the country [18]. It is still not clear whether WNV is endemic in Portugal, but the climate conditions are now definitely suitable for the transmission of the virus.…”