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Home / Equine Research Bank / Front Vet Sci / Reoccurrence of West Nile virus lineage 1 after 2-year decli...
Frontiers in veterinary science2023; 10; 1314738; doi: 10.3389/fvets.2023.1314738

Reoccurrence of West Nile virus lineage 1 after 2-year decline: first equine outbreak in Campania region.

Abstract: West Nile virus (WNV) is the most widespread arbovirus worldwide, responsible for severe neurological symptoms in humans as well as in horses and birds. The main reservoir and amplifier of the virus are birds, and migratory birds seem to have a key role in the introduction and spread of WNV during their migratory routes. WNV lineage 1 (L1) has been missing in Italy for almost 10 years, only to reappear in 2020 in two dead raptor birds in southern Italy. The present study reports the first equine outbreak in the Campania region. A 7-year-old horse died because of worsening neurological signs and underwent necropsy and biomolecular analyses. WNV-L1 was detected by real-time RT-PCR in the heart, brain, gut, liver, and spleen. Next Generation Sequence and phylogenetic analysis revealed that the strain responsible for the outbreak showed a nucleotide identity of over 98% with the strain found in 2 years earlier in the same area, belonging to the WNV-L1 Western-Mediterranean sub-cluster. These results underline that WNV-L1, after reintroduction in 2020, has probably silently circulated during a 2-year eclipse, with no positive sample revealed by both serological and biomolecular examinations in horses, birds, and mosquitoes. The climate changes that have occurred in the last decades are evolving the epidemiology of WNV, with introductions or re-introductions of the virus in areas that were previously considered low risk. Thereby, the virus may easily amplify and establish itself to reappear with sporadic evident cases in susceptible hosts after several months or even years.
Copyright © 2023 de Martinis, Cardillo, Pesce, Viscardi, Cozzolino, Paradiso, Cavallo, De Ascentis, Goffredo, Monaco, Savini, D’Orilia, Pinto and Fusco.
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Publication Date: 2023-11-30 PubMed ID: 38098986PubMed Central: PMC10720362DOI: 10.3389/fvets.2023.1314738Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study documents the reemergence of West Nile Virus lineage 1 (WNV-L1) in the Campania region of Italy, highlighting the first recorded equine outbreak there after nearly a decade of absence of this viral lineage.

Background on West Nile Virus (WNV)

  • WNV is the most widespread arbovirus worldwide, causing severe neurological disease in humans, horses, and birds.
  • Birds, especially migratory species, serve as the main reservoir and amplification hosts, facilitating virus introduction and spread along migration routes.
  • WNV has multiple genetic lineages; lineage 1 (L1) was absent in Italy for about 10 years before reappearing in 2020.

Purpose of the Study

  • To investigate and document the first equine outbreak caused by WNV-L1 in the Campania region, Southern Italy.
  • To analyze the viral strain involved via molecular methods and understand its relationship to previously detected strains.

Case Description and Diagnostic Findings

  • A 7-year-old horse presented neurological symptoms that worsened until death.
  • The horse underwent necropsy along with biomolecular testing (real-time RT-PCR) on multiple organs—the heart, brain, gut, liver, and spleen.
  • WNV-L1 was detected in all these tissues, confirming systemic infection.

Genetic Analysis and Viral Origin

  • Sequencing using Next Generation Sequencing (NGS) technology was performed on the viral genome isolated from the horse.
  • Phylogenetic analysis showed the viral strain had over 98% nucleotide identity to a WNV-L1 strain detected two years earlier in the same region.
  • The strain belongs to the Western-Mediterranean sub-cluster of WNV-L1, suggesting local persistence or reintroduction.

Implications of Silent Circulation

  • The virus likely circulated silently for about two years without detection by serology or molecular tests in horses, birds, or mosquitoes.
  • This silent, or eclipse, period means the virus was present but had not caused recognizable clinical or epidemiological signals in susceptible hosts.

Influence of Climate Change on WNV Epidemiology

  • Climate changes in recent decades may alter the epidemiology of WNV by expanding the range or frequency of virus introductions and reintroductions in areas previously considered low risk.
  • Environmental changes could promote conditions enabling the virus to establish reservoirs and amplifiers more readily.
  • As a result, WNV can reemerge sporadically with evident clinical cases after months or years of low activity, complicating disease surveillance and control.

Conclusions

  • This study documents a significant event in the epidemiology of WNV in Italy: the reoccurrence of lineage 1 associated with equine disease after a 2-year silent period.
  • The findings emphasize the need for ongoing surveillance in wildlife, vectors, and domestic animals to detect silent circulation and prevent outbreaks.
  • Climate and ecological changes must be considered in predicting and managing future WNV risks across Europe and similar regions.

Cite This Article

APA
de Martinis C, Cardillo L, Pesce F, Viscardi M, Cozzolino L, Paradiso R, Cavallo S, De Ascentis M, Goffredo M, Monaco F, Savini G, D'Orilia F, Pinto R, Fusco G. (2023). Reoccurrence of West Nile virus lineage 1 after 2-year decline: first equine outbreak in Campania region. Front Vet Sci, 10, 1314738. https://doi.org/10.3389/fvets.2023.1314738

Publication

Frontiers in veterinary science
ISSN: 2297-1769
NlmUniqueID: 101666658
Country: Switzerland
Language: English
Volume: 10
Pages: 1314738
PII: 1314738

Researcher Affiliations

de Martinis, Claudio
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Cardillo, Lorena
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Pesce, Federica
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Viscardi, Maurizio
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Cozzolino, Loredana
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Paradiso, Rubina
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
Cavallo, Stefania
  • Department of Epidemiologic and Biostatistics Regional Observatory (OREB), Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.
De Ascentis, Matteo
  • Istituto Zooprofilattico Sperimentale di Abruzzo e Molise, Teramo, Italy.
Goffredo, Maria
  • Istituto Zooprofilattico Sperimentale di Abruzzo e Molise, Teramo, Italy.
Monaco, Federica
  • Istituto Zooprofilattico Sperimentale di Abruzzo e Molise, Teramo, Italy.
Savini, Giovanni
  • Istituto Zooprofilattico Sperimentale di Abruzzo e Molise, Teramo, Italy.
D'Orilia, Francescantonio
  • Centro di riferimento regionale Sanità Animale (C.Re.San.), Nocera, Italy.
Pinto, Renato
  • U.O.D. Prevenzione e sanità pubblica veterinaria, Regione Campania, Napoli, Italy.
Fusco, Giovanna
  • Department of Animal Health, Istituto Zooprofilattico Sperimentale del Mezzogiorno, Portici, Italy.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Citations

This article has been cited 1 times.
  1. Golender N, Hoffmann B, Kenigswald G, Scheinin S, Kedmi M, Gleser D, Klement E. Bovine Ephemeral Fever Viruses in Israel 2014-2023: Genetic Characterization of Local and Emerging Strains.. Pathogens 2024 Jul 29;13(8).
    doi: 10.3390/pathogens13080636pubmed: 39204237google scholar: lookup
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