Topical use of 5% acyclovir cream for the treatment of occult and verrucous equine sarcoids: a double-blinded placebo-controlled study.
Authors: Haspeslagh Maarten, Jordana Garcia Mireia, Vlaminck Lieven E M, Martens Ann M
Journal: BMC veterinary research
Summary
# Editorial Summary: Topical Acyclovir for Equine Sarcoids Despite anecdotal reports of clinical benefit, a rigorous double-blinded, placebo-controlled trial has found no evidence that 5% acyclovir cream offers any advantage over placebo for treating occult and verrucous equine sarcoids. Forty-nine sarcoids across 24 horses received either topical acyclovir or placebo applied twice daily for six months, with lesions assessed monthly via photographic measurement of diameter and surface area, visual scoring of verrucosity, and PCR analysis of swabs for bovine papillomavirus (BPV) DNA. Critically, success rates, sarcoid size, surface area, and tissue changes showed no significant differences between treatment groups, with only a transient elevation in BPV DNA detection on acyclovir-treated lesions at the one-month mark—a finding that actually contradicts any therapeutic mechanism. These results align with the pharmacological rationale that acyclovir requires viral kinase activation to become effective, an enzymatic capacity BPV lacks, making this study a valuable cautionary example of why anecdotal improvement cannot substitute for controlled evidence when selecting sarcoid treatments. Practitioners should direct resources toward interventions with demonstrated efficacy rather than relying on topical antivirals for these notoriously challenging tumours.
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Practical Takeaways
- •Topical acyclovir cream is not an effective treatment for equine sarcoids and should not be relied upon as a primary or adjunctive therapy
- •The lack of the viral kinase necessary for acyclovir activation in BPV explains the absence of efficacy despite historical use claims
- •Alternative evidence-based sarcoid treatments should be pursued instead of investing time and resources in acyclovir applications
Key Findings
- •Topical 5% acyclovir cream showed no significant difference in success rates compared to placebo over 6 months of twice-daily treatment
- •No significant effect of acyclovir on sarcoid diameter, surface area, or verrucosity score versus placebo
- •BPV DNA positivity rates were significantly higher in acyclovir-treated tumours only at 1 month, with no difference at other timepoints
- •Results do not support the use of topical acyclovir for treatment of equine sarcoids despite previous anecdotal reports