Description of the first recorded major occurrence of equine viral arteritis in France.

This research paper describes the first significant outbreak of Equine Viral Arteritis (EVA) in France in 2007 and the use of molecular tools for its detection and management.

About Equine Viral Arteritis (EVA) and the Outbreak

Equine Viral Arteritis (EVA) is a disease generally prevalent in horses, and most instances of EVA infections are undetectable or mild. However, occasionally, the virus can cause severe outbreaks, as was the case in France in 2007. This particular outbreak was significant, causing not only mortality but also economic disruption. Over five counties in western France were impacted, with EVA detected in 18 distinct premises, including the original source (index) and 18 subsequent sites.

• The virus spread primarily through artificial insemination in draught horses.
• Eight fatalities were recorded, involving young foals, mature horses, and a fetus.
• 43 individuals tested positive through real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR).

Detection and Characterisation of EAV Strains

The research team used real-time RT-PCR to detect the presence of the EAV in various samples – blood, nasal swabs, semen, or organ samples.

• The cycle threshold (Ct) values, or the number of cycles needed in PCR to amplify the viral RNA to a detectable level, ranged from 19.8 to 40.4, depending on the samples.
• This was the first time that real-time RT-PCR was used to monitor an epidemic in horses, showcasing its effectiveness.
• The isolated strains were then characterised by sequencing the ORF5 fragment, providing insight into the specific type of EAV responsible for the outbreak.

Analysis of the EAV Strains

The analysis of the isolated strains showed that all 33 strains belonged to the EU-2 subgroup, indicating a common source. The high mortality rate associated with the outbreak signifies the virulence of this specific strain.

• Early detection of 3 signals with high Ct values illustrated the need to consider low signals in field conditions to prevent or manage future outbreaks effectively.

Conclusion

This research underscores the importance of molecular tools like RT-PCR for the early detection and management of viral outbreaks such as EVA. Also, continuous monitoring and analysis of such outbreaks can provide a better understanding of various viral strains, their virulence, spread mechanisms, and more, ultimately contributing to effective disease management strategies.