Horse news, research and information
Researchers report that the equine herpesvirus 1 (EHV-1) outbreak in the Pennsylvania stables in March was caused by a new variant of the H752 genotype.
The H752 genotype may cause neurological diseases. The research team reported that this new variant has a specific mutation in the ORF 30 gene, similar to the recent outbreak in France.
The mutation is located at a key nucleotide position, which has previously been shown to distinguish between neuropathic (D752) and non-neuropathic (N752) forms.
Nicola Pusterla and his researchers wrote in Pathogens that EHV-1 is described as an important and widely spread viral pathogen that can cause respiratory diseases in young horses, miscarriage of mares, and early foals. Death can occasionally cause neurological diseases.
Although nervous system problems are a relatively uncommon consequence, they can cause devastating losses and severely affect the horse industry.
On March 9, two authors, Julia Miller and Sarah Varnell, visited 31 horse show barns in rural Pennsylvania for routine dental care and vaccinations.
As part of the health assessment, 10 horses unexpectedly showed an increase in rectal temperature, although they all appeared bright and alert.
Collect blood and nasal secretions from feverish horses to check for common respiratory viruses, including EHV-1.
8 out of 10 horses tested positive for EHV-1. For the next 35 days, the abnormal physiological parameters of each of the 31 horses were monitored daily. Blood and nasal secretions are collected weekly for EHV-1 molecular testing, and blood is collected every 35 days to check for EHV-1 antibodies.
These horses include 14 gelding horses and 17 mares, ranging in age from 1 to 27 years old. Represents a variety of breeds, including 24 warm-blooded horses, four Welsh ponies, two thoroughbred horses, and a thoroughbred/purebred hybrid.
The virus causes poor health in 84% of animals, and 26 clinically infected horses have fever, loss of appetite, and swelling of the lower legs. Four horses showed mild short-term neurological problems.
The five horses did not show any abnormal clinical signs during the entire observation period.
The EHV-1 viral load is high in the blood and/or nasal secretions of diseased horses, while EHV-1 is mainly detected in the nasal secretions of horses with subclinical infections.
All 31 horses received valacyclovir treatment, and the clinically infected horses received further flunixin meglumine and heparin sodium.
When discussing their findings, the authors stated that one of the characteristics of this EHV-1 outbreak was that most horses did not show obvious clinical symptoms at the beginning of the investigation.
"One might argue that without early detection of EHV-1 and medical intervention, considering the neuropathic potential of the H752 genotype strain, more horses may develop spinal encephalopathy (brain inflammation)," they said.
They added that early medical intervention with valacyclovir in all performance horses may have prevented serious neurological consequences.
The fact that the attending veterinarian noticed an increase in rectal temperature without other clinical symptoms emphasizes the importance of regularly assessing the rectal temperature of at-risk horses.
They said that the horses in the study did not show respiratory symptoms, which may be because the horses were recently vaccinated against the respiratory form of EHV-1 as part of their vaccination plan.
Both H752 EHV-1 strains from France and Pennsylvania have shown the ability to cause neurological problems.
The authors say that the discovery of the new H752 genotype adds to the already complex pathophysiology and diagnostic challenges of EHV-1.
"Although the EHV-1 strains in France and Pennsylvania mainly cause a self-limiting disease characterized by fever, lethargy, anorexia, respiratory symptoms, and distal limb edema, they also show neuropathic potential.
"The distribution of the new H752 genotype in the horse herd is unclear," they added. The study also showed the highly infectious nature of the new H752 variant.
“Although it is almost impossible to prevent the transmission of equine alpha herpes virus in large horse operations, daily monitoring of horses at risk and the use of appropriate biosafety protocols around transporting horses may reduce the risk of EHV-1 transmission,” they said.
The research team consisted of Pusterla and Samantha Barnum of the University of California, Davis School of Veterinary Medicine; Miller and Varnell, working with Alliance Equine Health Care in Glenmore, Pennsylvania; Barbara Dallap-Schaer and Helen Aceto, New Bolton Center, University of Pennsylvania; and Aliza Simeone of the Pennsylvania Department of Agriculture.
Pustra, N.; Barnum, S. Miller, J. Varnell, S.; Dallap-Schaer, B.; Aceto, H.; Simeone, A. Investigation of the US EHV-1 outbreak caused by the new H752 genotype. Pathogens 2021, 10, 747. https://doi.org/10.3390/pathogens10060747
The research is released under a Creative Commons license and can be read here.
The latest research and information from the horse industry.
Your email address will not be published. Required places have been marked *
Save my name, email, and website in this browser for the next time you comment.
Notify me of followup comments via e-mail.
Notify me of new posts via email.
Aurora Pure Crabets Gerzanne Arabians Vollrath Hanoverians
Organization NZ Connemara Soc. NZ Farriers Assn. New Zealand Hanover Society Irish Draft Horse Association.
HomeWebsiteBryant Farrier Ltd The Pole Man Naturally Equine Advertising options