Use of antiviral medications against equine herpes virus associated disorders

Abstract

Summary Numerous types of equine herpesviruses (EHV) continue to afflict horses resulting in a variety of clinical manifestations. While many of the clinical manifestations of EHV are self‐limiting or require only supportive care, some clinical expressions of EHV infections cause severe risk to the horse's overall health and can result in abortion, long‐term deficits or death. Antiviral medications are infrequently utilised therapeutics in equine medicine and their exact efficacy is largely unknown. However, the use of antiviral medications may potentially decrease convalescent time and improve outcome in horses with EHV‐related diseases. Thus, equine practitioners should consider the potential use of antiviral medications in the future. The purpose of this article is to familiarise the equine practitioner with current information in regard to antiviral medications and their potential uses in equine medicine.

Successful outcome in a case of equine multinodular pulmonary fibrosis (EMPF) treated with valacyclovir

“…acyclovir per os q. 8 h. Acyclovir has a low bioavailability (3-8%), hence this reported dose rate does not lead to an Treatment of EMPF with valacyclovir effective plasma concentration (Wilkins et al 2005;Bentz et al 2006;Garré et al 2007;Wong et al 2010).…”

“…2007, 2009). Other authors have suggested a different dosing regime with a loading dose followed by a maintenance dose (Wong et al . 2010).…”

“…8 h which appeared to have a good bioavailability with sufficient plasma concentrations of acyclovir according to earlier studies (Garré et al 2007(Garré et al , 2009). Other authors have suggested a different dosing regime with a loading dose followed by a maintenance dose (Wong et al 2010). Wong et al (2008) suggested a treatment period of a few weeks for antiviral therapy of EMPF.…”

Effect of valacyclovir on EHV‐5 viral kinetics in horses with equine multinodular pulmonary fibrosis

“…Tetracycline antimicrobial drugs are often employed for their antifibrotic and anticollagenase effects . Use of the antiviral prodrug valacyclovir has been described in 1 horse with EMPF that was reported to be clinically healthy 2 years after treatment . Valacyclovir is produced by ester linking of acyclovir with the amino acid l ‐valine, increasing the drug's oral bioavailability.…”

Equine multinodular pulmonary fibrosis: Diagnosis and treatment

“…The use of acyclovir or valacyclovir (an acyclovir prodrug with greater bioavailability when administered orally) is speculative, based on studies evaluating efficacy against EHV-1 in clinical studies ongoing at the time the initial reported cases of EMPF were being studied, although a targeted antiviral approach would seem to be beneficial (Wilkins et al 2003;Wilkins 2004;Henninger et al 2007;Wong et al 2010). Although the pathogenic role of EHV-5 remains to be fully proven -and the susceptibility of equine g-herpes viruses to acyclovir is unknown -the Epstein-Barr virus, a human g-herpes virus, is reportedly susceptible (Billaud et al 2009).…”