Q: I have heard that equine sarcoids are linked to the bovine pap virus. Can sarcoids be passed from cattle to horses?
Sarcoids are tumours that occur in the horse, only affecting the skin. Some types of the bovine papillomavirus (BPV) are associated with development of sarcoids. However, experts are still looking into the modes of transmission, for example being passed by flies to equine wound sites, or via contaminated pasture.
Researchers at the University of Glasgow’s Institute of Comparative Medicine recently stated that BPV is the only pap virus that jumps species, as it infects equids (ref 1). A further study this year by researchers at Belgium’s Ghent University (ref 2) found that BPV can be detected in normal (non-cancerous) equine skin, suggesting that some horses are simply carriers.
We asked vet Deborah Pett, of Cinder Hill Equine Clinic in Sussex, for her take on the situation.
“This is a very good question and sarcoids have certainly previously been considered to be non-infectious,” she said. “However, while there is much evidence to support the involvement of BPV in the development of equine sarcoids, the fact is that currently we do not know for certain whether sarcoids are contagious or not and genetics and breed type also appear to contribute to susceptibility.
“DNA fragments from BPV have also been detected in flies, supporting the proposal that flies may act as the vector for the virus, carrying it from place to place, and possibly from cow to horse. Therefore, if it does emerge that BPV is the causative agent, direct or indirect contact between cow and horse may not be necessary for transmission. At our veterinary practice, we have not seen a link between horses with sarcoids and contact with cattle, but it will certainly be interesting to see what further evidence emerges in the future.”
H&H vet Karen Coumbe, from Bell Equine Veterinary Clinic in Kent, added: “Sarcoids most commonly appear on the areas of a horse’s anatomy where flies congregate, such as around the eyes, the groin or at the site of healing wounds. This has made me suspect flies as part of the cause, as they may well carry virus particles, or indeed other ‘nasties’ from cattle, horses or elsewhere.
“Although cattle may well be incriminated, I think one should also consider the possible risk of other horses affected with sarcoids, especially if there are sarcoids that are traumatised, so that they bleed and attract flies.
“Certainly, there is evidence of a hereditary influence on the development of sarcoids, so some horses may well be more susceptible than others,” said Karen. “It also highlights the need for effective fly control.”
Bell Equine Vet Clinic, tel: 01622 813700 www.bellequine.com
Cinder Hill Equine Clinic, tel: 01342 811335 www.cinderhillequinevets.co.uk
Ref 1: Vet Dermatol. Oct. 2008. 19(5):243-54. “Bovine papillomaviruses: their role in the aetiology of cutaneous tumours of bovids and equids.” L Nasir et al.
Ref 2: Vet Microbiol. May 2008. 25;129(1-2):58-68. “High prevalence of bovine papillomaviral DNA in the normal skin of equine sarcoid-affected and healthy horses.” L Bogaert et al.
This article was first published in Horse & Hound (8 January, ’09)