Three new equine parvoviruses appear unlinked to respiratory disease – study

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More work is required to learn about the clinical relevance of recently discovered equine parvoviruses, according to scientists.
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Three recently discovered equine parvoviruses do not appear to contribute to respiratory disease in horses, researchers report.

Equine parvovirus hepatitis (EqPV-H), equine parvovirus CSF (EqPV-CSF) and equine copivirus (Eqcopivirus) were first identified in horses with respiratory signs, although their clinical relevance has largely remained elusive.

Equine parvovirus hepatitis is the most investigated to date, having been linked to clinical and subclinical hepatitis. However, reports on the other two have been sparse.

Equine parvovirus CSF was initially found in the cerebrospinal fluid of a horse with neurological signs and has since then been reported in serum and nasal secretions of both clinically healthy horses and horses with fever and respiratory signs.

To the researchers’ knowledge, only one report has documented the genomic presence of Eqcopivirus in blood or nasal secretions of healthy horses, and those with respiratory signs.

Nicola Pusterla and his fellow researchers set out to investigate whether the three parvoviruses were present in the blood and nasal fluid samples of both clinically healthy horses and those with acute onset of respiratory disease.

The study team, writing in the journal Animals, said the detection of any of the three newly identified parvoviruses in nasal fluid samples is relevant, as viral shedding can contribute to environmental contamination, with direct or indirect transmission to other susceptible horses.

The researchers used molecular-based methods to test blood and nasal secretions from 667 equids with acute onset of fever and respiratory signs, as well as from 87 clinically healthy horses.

They reported that 117 of the sick horses returned a positive test for at least one of the three parvoviruses. Ten of the clinically healthy horses also tested positive for one of the equine parvoviruses.

The frequency of detection of the three parvoviruses was similar between the sick and clinically healthy horses, suggesting that these newly characterized viruses do not appear to contribute to the clinical picture of equids with respiratory disease.

The study team also tested for the presence of common equine respiratory pathogens. Co-infections with these respiratory pathogens and parvoviruses were seen in 39 of the sick animals.

Blood was the predominant sample positive for EqPV-H and equine parvovirus EqPV-CSF, while blood and nasal fluid samples tested positive for Eqcopivirus with similar frequencies.

It appears that the three viruses may have a species affinity, as all 15 donkeys and mules tested negative for the three parvoviruses.

The authors noted that, since the initial characterization of the three viruses, two additional equine parvoviruses and a previously unknown picornavirus have been described in the tissues of horses with interstitial pneumonia.

In order to prove the clinical relevance of any of these new equine parvoviruses, experimental challenge studies will be required, they said.

The study team comprised Pusterla and Samantha Barnum, with the School of Veterinary Medicine at the University of California, Davis; Kaitlyn James, with Massachusetts General Hospital in Boston; and Eric Delwart, with the Vitalant Research Institute in San Francisco.

Pusterla, N.; James, K.; Barnum, S.; Delwart, E. Investigation of Three Newly Identified Equine Parvoviruses in Blood and Nasal Fluid Samples of Clinically Healthy Horses and Horses with Acute Onset of Respiratory Disease. Animals 2021, 11, 3006. https://doi.org/10.3390/ani11103006

The study, published under a Creative Commons License, can be read here

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