Can Antiviral Drug Treatment be Successful for Equine Herpesvirus?
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Can antiviral drugs be used to successfully treat horses with equine herpesvirus? Recent research into the drug Valacyclovir (trade name Valtrex) seems to indicate it has a place in treating horses exposed to--and diagnosed with--equine herpesvirus.
Numerous outbreaks of neurological disease due to a variant strain of equine herpesvirus-1 (EHV-1) in the past few years has prompted an increase in related research in equine herpesvirus (EHV). Unfortunately, the outbreaks have also led to increased misinformation regarding the findings and conclusions that have been reached. Some of this research has entailed new approaches to the management and treatment of disease caused by EHV.
Veterinarians discussed acyclovir as a possible treatment option, however the therapy was unsubstantiated for use in horses. Two abstracts presented at the 2005 Forum for the American College of Veterinary Internal Medicine, and subsequently published in veterinary journals, have sought to evaluate the utility of the use of acyclovir for equine herpesvirus by defining the drug's behavior in the horse through pharmacokinetic analysis. Both of these papers concluded that horses could not absorb enough of the drug to be effective against EHV,
Researchers then turned their attention to valacyclovir (Valtrex®), a prodrug (altered to be absorbed intestinally, where it is acted upon by enzymes to produce the active drug, acyclovir).
The initial investigations of valacyclovir in the horse are strongly supportive of much better absorption, and therefore, the ability to attain high enough concentrations in the body to be effective against EHV.
Valtrex has now been utilized successfully and appears to have been helpful in containing and treating many of the recent outbreaks of EHV-1 encephalomyelitis. According to reports, the drug has successfully been used to reduce fever and keep exposed horses from developing neurologic signs, as well as treating neurologic horses, which subsequently improved significantly. Some of these horses had been down and were able to stand again after treatment.
The same investigators are in the planning phases of a challenge study in which the clinical changes in response to various antiviral drugs are compared in horses that have been challenged with herpes virus. More specific information regarding dosages, dosage intervals, herpesvirus sensitivity to the drug, and other antiviral approaches are on the horizon.
by: Bradford G. Bentz, VMD, MS, Dipl. ACVIM, ABVP (equine), Hagyard Equine Medical Institute
Related EHV1 Articles:
Jan 9, 2007 - EHV-1, Daily Status Table and Definitions. Of the 13 infected horses 7 have neurological signs. Read more>
Jan. 7th & 8th, 2007 - No new clinical cases reported. No new quarantines issued. Quarantine at Payson Park modified on 01/06/07 Read more>
Jan. 4, 5, & 6, 2007 No new clinical cases reported. No new quarantines issued. Read more>
Jan. 1, 2 & 3, 2007, & Dec. 31st, 2006- No new clinical cases reported for the past 4 days. No new quarantines issued. Read more>
Dec. 30, 2006 8pm, One new death, one new clinical case at Palm Beach Equine Sports Complex already under state quarantine. AM: One new presumed infected case located at a facility already under state quarantine.
Dec. 30, 2006 8pm, Current Situation: One new death, one new clinical case at Palm Beach Equine Sports Complex already under state quarantine. No new quarantines issued today. AM: One new presumed infected case located at a facility already under state quarantine.
Dec. 29, 2006 Current Situation: One new confirmed case of equine herpesvirus located at a facility already under state quarantine. No new quarantines issued as of Dec. 28th
Dec. 28, 2006 No new confirmed cases or quarantines at this time. Three strike teams collected temperature check charts, stall inventories, and trainer contacts from all facilities under mandatory state quarantine. Dr. Diane Kitchen is tracing movements of the exposed and infected horses. Dr. Mike Short is corresponding with area veterinarians on health and testing issues. Public Information Officer Mark Fagan is preparing Spanish language information sheets for distribution. (FLSART)
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