Sarcoids are believed to be associated with bovine papillomavirus type 1 (BPV1). The virus is implicated in the transformation of equine skin cells, resulting in tumour development. Although the exact transmission route is not fully understood, BPV1 DNA has been detected in many equine sarcoid lesions, strengthening the link between the virus and the disease.
Currently there is no universally effective treatment, and if treatment fails the sarcoids will often come back worse than they were in the first place. Although the disease is rarely life-threatening, many horses with sarcoids are euthanased because the condition is untreatable or because the horse is unsellable.
Various treatment options are available for equine sarcoids, including: surgical removal, laser excision, cryotherapy (freezing the tumour), topical and intralesional chemotherapy and immunotherapy.
However, treating sarcoids is challenging due to their high recurrence rates, especially following surgical removal. Residual tumour cells left behind during surgery often lead to regrowth, making long-term management difficult.
Currently, there is no approved vaccine available to prevent or treat equine sarcoids. However, given the association with BPV1, the development of a vaccine could potentially offer protection against the disease.
Researchers at the Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, have made a significant step toward developing a sarcoid vaccine.
A team led by Olivia Jacob and colleagues has developed an experimental vaccine using a recombinant baculovirus vector. This vaccine expresses the L1 protein of BPV1.
(The L1 protein is a major structural component of the BPV1 viral capsid. It plays a key role in triggering the immune system to recognize and neutralize the virus, making it a prime target for vaccine development.)
The researchers conducted a trial involving 15 horses. Ten healthy, sarcoid-free horses received two doses of the experimental vaccine, administered three weeks apart. Five control horses were injected with a placebo vaccine containing only the culture medium.
Blood samples were collected before and after vaccination to assess the immune response.
Vaccinated horses produced strong neutralising antibody responses, with antibody titres ranging from 40 to over 1280. In contrast, the control horses showed no detectable immune response.
The researchers concluded that since neutralising antibodies are recognised as an indicator of protection against BPV1, this experimental vaccine has the potential to protect horses from developing sarcoids.
The study offers promising evidence that a BPV1-based vaccine could provide immunity against equine sarcoids. Although still in the experimental stage, the vaccine demonstrated a good safety profile and the ability to elicit a strong immune response in horses. If further trials confirm its effectiveness, this vaccine could provide a novel tool in preventing and managing equine sarcoids, significantly improving equine health and welfare.
For more details, see:
O. Jacob, B. Hause, K. Peters-Smith, E.N. Adam, A.E. Page, C. Floyd, C. Tucker, L.G. Eertink, D. Wang, F. Li,
Safety and immunogenicity of a sarcoid vaccine in horses,
Journal of Equine Veterinary Science,(2025) 146, 105381,
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