Unwelcome extras

Sarcoids are the most common skin tumours in horses and represent about 90% of the skin tumours seen in horses worldwide. Robyn Graham MRCVS demystifies them

- Robyn Graham

SARCOIDS can occur in a number of different forms, and their clinical significance and so impact on the horse - will also vary. They can be small and benign or extensive and spread rapidly into surrounding tissues.

Sarcoids are classified into six types and horses may have more than one type at the same time. They must be assessed on an individual basis, so always consult your vet if you think your horse may have a sarcoid.

There have been no reports of spread to internal organs (metastasis) but that does not make them any less devastating given the potential impact they may have on the function or aesthetics, or both, of the horse based on tumour location, size and frequency.

They are linked to the bovine papillomavirus, although genetic susceptibility seems to play a large part in whether horses infected with the virus will go on to develop sarcoids. Concerns about the spread of the virus by flies or direct contact between horses are widespread among horse owners; however such spread has never been proven to occur.

The most common locations for sarcoids reported are around the head (on the eye, ear or lips) and neck (39% of those in the most common locations), extremities (35%) and ventrum (underside of the body) including groin (26%).

● Occult sarcoids are thought to represent the earliest forms of the disease and appear as circular alopecic (hairless) areas or areas of different hair quality (thickening and scaliness). They can sometimes be mistaken for rubs from rugs or tack, or ringworm lesions.

● Verrucose sarcoids tend to have a grey, scaly and wart-like appearance, with flaking off a common occurrence. Multiple lesions can coalesce over time and affect a large area. Small nodules or papillomas can sometimes be felt.