The West Nile virus, an enveloped, single-stranded RNA virus transmitted to humans and animals via mosquitoes and birds, has become a growing public health concern globally.
In a recent study published in the journal PLOS Pathogens, scientists delve into the transmission dynamics of the West Nile virus (WNV) in Europe, identifying agricultural land use and bird movements as the primary factors responsible for outbreaks of this mosquito-borne virus.
The study, titled “West Nile Virus Spread in Europe: Phylogeographic Pattern Analysis and Key Drivers,” sheds light on the evolving patterns of WNV and underscores the importance of addressing the impact of human activities on viral transmission.
The West Nile virus, an enveloped, single-stranded RNA virus transmitted to humans and animals via mosquitoes and birds, has become a growing public health concern globally.
Since its first detection in Europe in 1960, the virus has seen an uptick in outbreaks, particularly in Southeast and Central Europe since 1996. The study focuses on understanding the transmission dynamics of different WNV lineages, with a particular emphasis on the prevalent WNV-2a sub-lineage, which accounts for 73% of publicly available viral sequences in Europe.
The scientists employed a comprehensive approach, incorporating WNV genome sequences, ecological data, and epidemiological information into phylodynamic models to map the evolution and transmission history of WNV in Europe.
Spatially explicit phylogeographic models were developed to assess the impact of various factors on viral dispersal direction and velocity. Additionally, a skygrid-generalized linear model (GLM) was used to examine how changes in environmental temperature and biodiversity correlated with variations in viral genetic diversity over the past two decades.
The study’s findings revealed distinct evolutionary pathways for different WNV lineages, with WNV-2a identified as the predominant sub-lineage in Europe. It had evolved into two major co-circulating clusters (clusters A and B) over the past two decades, spreading to the west and south from its origin in Central Europe. The dispersal velocity of WNV-2a, estimated at 88 to 215 kilometers per year, was found to correlate with bird movements.
Agricultural land use emerged as a significant factor influencing the spread of WNV, with factors related to crops and livestock production showing positive associations with dispersal velocity and transmission direction.
The study identified coverage of agricultural land, pasture, cultivated and managed vegetation, and livestock density as key contributors to the transmission dynamics of WNV. Additionally, wetland coverage and migratory bird flyways were positively associated with transmission direction.
The scientists hypothesized that WNV-2a was likely introduced to Europe via long-distance migratory birds. As the virus circulated in local bird populations and other hosts, it evolved and diversified, transmitting throughout the European continent. The high dispersal velocity of WNV-2a, influenced by bird movements and agricultural land use, raised concerns about the increased transmission of the virus to new territories.
The study emphasizes the need for strengthened virological surveillance in Central Europe, where WNV outbreaks are more likely to occur. Regions with high farming density also warrant increased surveillance due to their association with agricultural land use, which impacts mosquito and bird diversity, as well as aquatic habitats.
The loss of natural ecosystems and alterations in birds’ migration routes, attributed to high-level agricultural activities, were identified as contributors to the increased transmission of WNV in urban locations.
In conclusion, the study underscores the complex interplay between agricultural practices, bird movements, and the transmission dynamics of the West Nile virus in Europe. As the world grapples with emerging infectious diseases, understanding these factors becomes crucial in devising effective strategies for surveillance, prevention, and control to safeguard both human and animal health.