West Nile virus in Portugal: insights from equine serology.
4 affiliations
- 1National Institute for Agrarian and Veterinary Research (INIAV, I.P.), Av. da República, Quinta do Marquês, Oeiras, 2780-157, Portugal.
- 2Centre for Interdisciplinary Research in Animal Health (CIISA), Lisbon, Portugal.
- 3National Institute for Agrarian and Veterinary Research (INIAV, I.P.), Av. da República, Quinta do Marquês, Oeiras, 2780-157, Portugal. [email protected].
- 4Department of Life Sciences, NOVA School of Science and Technology, Caparica, Portugal. [email protected].
Abstract
Background
West Nile virus (WNV) is a zoonotic mosquito-borne flavivirus belonging to the family Flaviviridae and the genus Orthoflavivirus. It is primarily transmitted by Culex spp. mosquitoes and maintained in an enzootic cycle involving avian hosts. Humans and horses are considered incidental or dead-end hosts, as they do not sustain onward transmission due to their low viremia levels, although infections may progress to severe neurological disease and death. In Portugal, WNV has circulated in horses almost annually since its first detection in 2004, suggesting endemic establishment.Results
This study provides updated data on the geographical distribution and annual occurrence of WNV infection in clinically affected horses in mainland Portugal between 2022 and 2025, thereby contributing to a broader understanding of WNV dynamics in southern Europe. As viremia is typically low and short-lived in horses, diagnosis relies primarily on serological methods, particularly the detection of IgM antibodies. IgM analyses identified WNV-seropositive horses in all four years, with 3/9 cases (33.3%) testing positive in 2022, 15/30 (50.0%) in 2023, 32/52 (61.5%) in 2024, and 13/38 (34.2%) in 2025. No WNV RNA was detected in serum samples. Based on clinical signs together with serological results, WNV was diagnosed in 63 of the 129 horses presenting neurological signs.Conclusions
These findings reinforce the continued circulation of WNV in Portugal and highlight the importance of sustained surveillance in equine populations.
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BibTeX
@article{maroco2026west,
title = {{West Nile virus in Portugal: insights from equine serology.}},
author = {D Maroco and F Ramos and F Abade Dos Santos and A M Henriques and A Duarte and M Duarte and S C Barros},
journal = {BMC veterinary research},
year = {2026},
month = jul,
doi = {10.1186/s12917-026-05756-6},
url = {https://europepmc.org/article/MED/42958220},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - West Nile virus in Portugal: insights from equine serology.
AU - D Maroco
AU - F Ramos
AU - F Abade Dos Santos
AU - A M Henriques
AU - A Duarte
AU - M Duarte
AU - S C Barros
PY - 2026
DA - 2026/07/30
JO - BMC veterinary research
DO - 10.1186/s12917-026-05756-6
UR - https://europepmc.org/article/MED/42958220
AB - Background West Nile virus (WNV) is a zoonotic mosquito-borne flavivirus belonging to the family Flaviviridae and the genus Orthoflavivirus. It is primarily transmitted by Culex spp. mosquitoes and maintained in an enzootic cycle involving avian hosts. Humans and horses are considered incidental or dead-end hosts, as they do not sustain onward transmission due to their low viremia levels, although infections may progress to severe neurological disease and death. In Portugal, WNV has circulated in horses almost annually since its first detection in 2004, suggesting endemic establishment.Results This study provides updated data on the geographical distribution and annual occurrence of WNV infection in clinically affected horses in mainland Portugal between 2022 and 2025, thereby contributing to a broader understanding of WNV dynamics in southern Europe. As viremia is typically low and short-lived in horses, diagnosis relies primarily on serological methods, particularly the detection of IgM antibodies. IgM analyses identified WNV-seropositive horses in all four years, with 3/9 cases (33.3%) testing positive in 2022, 15/30 (50.0%) in 2023, 32/52 (61.5%) in 2024, and 13/38 (34.2%) in 2025. No WNV RNA was detected in serum samples. Based on clinical signs together with serological results, WNV was diagnosed in 63 of the 129 horses presenting neurological signs.Conclusions These findings reinforce the continued circulation of WNV in Portugal and highlight the importance of sustained surveillance in equine populations.
SN - 1746-6148
ER -