Increasing Seroprevalence In Horses Evidences Widespread Circulation Of West Nile Virus In Albania.

Overview

• This study investigated the prevalence of West Nile virus (WNV) antibodies in horses across Albania, showing significant and widespread exposure to the virus from 2017 to 2020.

Introduction to West Nile Virus and Its Monitoring

• West Nile virus (WNV) is a mosquito-transmitted flavivirus causing West Nile disease, which affects both humans and animals, including horses.
• It is considered an emerging and re-emerging infectious disease with significant global health implications.
• Horses serve as important sentinel species because they can indicate active WNV circulation in a region.
• Due to short periods of virus presence (viraemia) and low viral loads in horses’ blood, the infection is primarily monitored by detecting antibodies rather than by direct viral detection.

Aim and Methodology

• The main objective was to estimate how many horses in Albania had been exposed to WNV by measuring their antibody levels.
• Sample Collection: 509 serum samples were taken from apparently healthy and unvaccinated horses between 2017 and 2020 across various regions of Albania.
• Testing Methods: Two commercial enzyme-linked immunosorbent assay (ELISA) kits were used: one detecting total WNV-specific antibodies, and another detecting WNV-specific IgM antibodies (which indicate recent infection).
• A subset of ELISA-positive samples (37) was further tested with the virus neutralisation test (VNT), which is considered the gold standard confirmatory test for WNV antibodies.

Results

• From the 509 tested samples:
  • 143 samples (28.1%) tested positive for total WNV antibodies, showing previous exposure.
  • 12 samples (2.35%) tested positive for IgM antibodies, indicating recent infection.
• No horses tested positive for both total antibodies and IgM simultaneously, so the combined seroprevalence was 30.5% (155/509).
• The virus neutralisation test confirmed WNV-neutralising antibodies in 35 out of 37 tested ELISA-positive samples (94.6%), with varying antibody levels (titres from 1:10 to 1:640), supporting the ELISA findings.

Interpretation and Significance

• The high seroprevalence indicates widespread circulation of WNV in horses throughout Albania during the study period.
• The detection of IgM-positive horses suggests active or recent transmission cycles within the regions sampled.
• Compared to earlier surveillance data (from 2010-2011), there was an increase in seropositivity and expansion of WNV exposure into areas previously unaffected.
• This trend highlights a growing public and animal health concern and the dynamic nature of WNV transmission in Albania.

Conclusions and Recommendations

• This study underscores the importance of ongoing surveillance for WNV in horses as sentinels, to monitor disease activity and potential spillover into humans.
• Given the increasing seroprevalence and geographic spread, integrated veterinary and public health efforts are needed to track and control WNV circulation.
• Monitoring should include serological surveillance, vector control (targeting mosquitoes), and awareness campaigns for horse owners and health officials.
• Further research may be required to understand ecological and climatic factors driving the spread, and to evaluate risks to other species including humans.