New Treatment for Equine Herpesvirus Tested in Horses

A novel experimental treatment for equine herpesvirus type-1 (EHV-1) called RNA interference shows promise, but more research is needed before this technology becomes commercially available.

EHV-1 evades the horse's immune system during infection and can lie dormant in the horse's body. For these reasons, making an effective vaccine against EHV-1 has, and continues to be, a challenge.

While EHV-1 usually causes mild disease, reproductive losses, lost training and competition days, and death secondary to neurologic disease can also occur. To date, treatment remains largely supportive.

"The failure of conventional drugs and vaccines to produce the desired level of protection has led to the investigation of alternative technologies for preventing and treatment of EHV-1-associated clinical disease," reported a group of researchers led by Nikolaus Osterrieder, DVM, DVM Habilitation (equivalent to PhD), from the Institute of Virology at the Freie Universitat Berlin in Germany and the Department of Clinical Sciences at Cornell University's College of Veterinary Medicine.

RNA interference, which has shown promise in other species, involves the use of small RNA molecules to degrade important target genes such as those that the virus needs to enter and infect host cells, thereby halting progression of disease.

Osterrieder and colleagues evaluated the use of RNA interference for protecting in-contact horses during EHV-1 outbreaks. Fourteen horses were randomly divided into treatment and control groups. All horses were infected with neurologic EHV-1 virus intranasally. Horses in the treatment group also received interfering RNA 12 hours before and after exposure to EHV-1.

The researchers reported that significantly fewer treated horses required humane euthanasia due to intractable neurologic signs, as compared to control horses.

No significant difference in viral shedding or viremia (spread of the virus in the blood stream) was noted between the two groups. Nonetheless, the researchers believe that modification of the technique and/or dosing regimen will result in improved outcomes on these parameters. Research is ongoing.

The study, "The Effect of siRNA Treatment on Experimental Equine Herpesvirus Type 1 (EHV-1) Infection in Horses," is scheduled to be published in an upcoming edition of the journal Virus Research. The abstract is available on PubMed.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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