Isolation and Identification of Emerging Equine Encephalosis Virus Serotype 6 in Israel, 2023.

Overview

• Researchers isolated and identified Equine Encephalosis Virus (EEV) serotype 6 in Israel for the first time in 2023.
• This discovery suggests the virus may have a wider geographical presence than previously understood and has implications for equine health monitoring.

Background and Significance

• Equine encephalosis (EE) is a viral disease transmitted by arthropods, primarily affecting equid species such as horses and donkeys.
• The disease is similar but generally milder than African horse sickness (AHS), a more severe viral disease of horses.
• Before this study, Israel had only reported cases of EE caused by serotype 4 of the virus (EEV-4), with sporadic outbreaks documented.
• The emergence of a different serotype indicates potential changes in the virus’s distribution or introduction of new viral strains.

Methods

• Clinically diagnosed EE cases in horses and donkeys during summer 2023 prompted laboratory investigation.
• Whole blood samples were collected from affected animals to isolate the virus.
• Researchers inoculated tissue cultures with these blood samples in order to grow and isolate the virus.
• Successful virus isolation was confirmed using:
  • Conventional reverse transcription PCR (RT-PCR) to detect viral genetic material.
  • Sanger sequencing of multiple viral genes to identify the genetic characteristics of the virus.
• BLAST (Basic Local Alignment Search Tool) analysis was used on genome segment 2 to determine the serotype of the isolated virus strains.
• One representative virus strain underwent full-genome sequencing to provide a comprehensive genetic profile.
• Phylogenetic analysis compared this genome to known EEV sequences globally to understand its evolutionary and epidemiological relationship.

Key Findings

• Five EEV isolates were recovered from sick animals’ blood samples.
• All isolates were identified as serotype 6 (EEV-6), marking the first identification of this serotype in Israel.
• Full-genome sequencing and analysis showed a close genetic relationship between the Israeli EEV-6 strains and strains previously found in South Africa and India.
• This genetic relatedness implies potential epidemiological connections, such as virus spread or introduction from other geographic regions.

Implications and Conclusions

• The detection of EEV-6, alongside previous reports of EEV-4, suggests that multiple serotypes circulate in Israel.
• The discovery expands the understanding of EEV’s geographic distribution, indicating the virus might be more widely spread than previously assumed.
• These findings call for enhanced surveillance and molecular epidemiology studies to monitor EEV circulation and assess potential risks to equid populations.
• Understanding the virus’s movement and genetic diversity is critical for disease control, prevention strategies, and guiding veterinary public health measures.
• Further investigation is warranted to explore the modes of virus introduction and transmission pathways linking Israel, South Africa, India, and possibly other regions.