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An antiviral drug developed for the treatment of herpes simplex virus infections in humans performed no better than a placebo in tackling equine sarcoids, researchers report.
Maarten Haspeslagh and his colleagues from Ghent University in Belgium noted that previous studies had mentioned the use of topical acyclovir for the treatment of equine sarcoids.
Acyclovir (acycloguanosine) is an antiviral drug developed for the treatment of herpes simplex virus cases in humans. It has also been found to inhibit viral replication for some other viruses.
In one reported study, topical treatment with acyclovir resulted in complete regression in 68% of occult, verrucous, nodular or mixed equine sarcoids.
Success rates with it were reported to vary, they noted, and, since the bovine papillomavirus lacked the presence of a particular enzyme necessary to activate acyclovir, there was no proof of its activity against equine sarcoids.
Many treatments had been reported for equine sarcoids, they added, but no universal treatment has been found to cure all sarcoids on all body locations.
The study team, writing in the journal BMC Veterinary Research, described an experiment in which owners treated 24 equine sarcoids by applying acyclovir cream and 25 with a placebo. The placebo was the same cream formulation but without the acyclovir.
Both creams were applied twice daily for six months.
Before the start of treatment, and each month, photographs and swabs were obtained of the sarcoids. Each sarcoid’s diameter and surface area was measured, and their appearance was visually assessed on a visual analog scale. The swabs were analysed for the presence of bovine papillomavirus DNA.
Success rates were not significantly different between the acyclovir and placebo groups, the researchers reported. There was also no significant effect of treatment on sarcoid diameter, surface area, or their visual appearance.
For the swabs, a significantly higher bovine papillomavirus positivity rate was found for acyclovir-treated tumours compared to placebo-treated sarcoids only after one month of treatment, but not at other time points.
In the placebo group, a clear and significant decrease in the positivity rate could be seen over time, which was not the case for acyclovir-treated tumours. “No plausible explanation could be given for this observation,” they said.
“None of the results indicate that treatment with acyclovir yields any better results compared to placebo treatment,” the researchers concluded.
The study team comprised Haspeslagh, Mireia Jordana Garcia, Lieven Vlaminck and Ann Martens.
Topical use of 5% acyclovir cream for the treatment of occult and verrucous equine sarcoids: a double-blinded placebo-controlled study
Maarten Haspeslagh, Mireia Jordana Garcia, Lieven E. M. Vlaminck and Ann M. Martens
BMC Veterinary Research 2017 13:296 https://doi.org/10.1186/s12917-017-1215-0