Viruses detected for the first time in Swedish horses

Viral infections are a major threat to animal welfare and can also cause significant economic losses in the horse industry. One of the first signs of a viral infection is fever, but often the underlying cause of the fever is not identified at this early stage.

In this study, viral metagenomics, i.e. large-scale sequencing and bioinformatics analysis, was used to identify viruses in serum and nasal swabs from horses with and without fever. The advantage of this method, compared to more traditional diagnostic methods, is that all viruses in a sample are detected simultaneously without having to decide in advance which virus to look for.

In the nasal swabs, mainly different types of herpes viruses were found, which was expected as these viruses are known to circulate in Sweden. But interestingly, equine torque tenovirus and equine copiparvovirus were also detected in the nasal swabs. These viruses were also found in the blood samples, along with equine circovirus and equine pegivirus, among others.

The majority of the different viruses discovered have never been reported before in Sweden - or even in Europe, but have only been previously described in the USA and in some cases in China and their potential impact on equine health is still unknown. Since these viruses are new to Sweden, and Europe, in most cases the entire viral genome was characterized.

In conclusion, the study provides important new knowledge about the viral flora of Swedish horses and enables further studies on the spread of these viruses and their possible links to disease - something that can ultimately contribute to better equine health and infection control.

Link to the article

Blomström, AL., Källse, A. & Riihimäki, M. Detection and genetic characterization of equine viruses in Sweden using viral metagenomics. BMC Vet Res 21, 119 (2025)