Phylogenetic characterisation of the G(L) sequences of equine arteritis virus isolated from semen of asymptomatic stallions and fatal cases of equine viral arteritis in Denmark.

This research investigates the genetic relationships between strains of equine arteritis virus (EAV) found in healthy horses and those causing fatal disease in Denmark. The team found a wide range of EAV genetic variants in the local horse population, highlighting a potential source of severe equine viral arteritis (EVA) infections in the future.

Research Context

• This study was conducted to understand the genetic relationship between strains of EAV isolated from healthy, virus-shedding stallions and those resulting in fatal cases of EVA in Denmark.
• EAV is an infectious virus that can cause a variety of symptoms in horses, ranging from mild fever and respiratory issues to potentially fatal cases of EVA.
• The infection can become persistent in stallions, who then become asymptomatic carriers, shedding the virus in their semen and potentially passing it on to mares during natural or artificial breeding.

Methodology

• The researchers isolated EAV from three deceased foals and an aborted fetus during three separate EVA outbreaks.
• Using a technique called reverse transcription-polymerase chain reaction (RT-PCR), the researchers were able to amplify and sequence the part of EAV genome responsible for encoding the EAV G(L) protein, a component of the virus critical to its infectivity.
• The team also obtained DNA sequences from virus samples collected from semen of seven asymptomatic, virus-shedding stallions.

Results and Findings

• Upon analyzing and comparing these DNA sequences, the researchers found variations of 0-14% at the nucleotide level (the basic structural units of DNA) and 0-10% at the protein level.
• Their phylogenetic analysis, which looks at the evolutionary relationships between different strains of the virus, revealed that both European and North American “types” of EAV were present in Denmark.
• This applied to both asymptomatic carrier stallions and fatal cases of EVA, highlighting the potential for a variety of EAV types to cause severe disease in horses.

Conclusion

• This study reveals that the asymptomatic carrier stallions shedding EAV in their semen in Denmark are a potential source of severe EVA in the local horse population.
• This information can help in devising effective surveillance and control strategies for preventing EVA outbreaks in Denmark and other countries with similar circumstances.