Equine sarcoid

  Equine Sarcoids or Sarcoids are common, usually benign, skin tumours of horses and other equidae which have several different forms.

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Aetiology

The cause is not fully understood but a viral cause is suspected. In particular, bovine papillomavirus types 1 and 2 have been implicated.^[1]

Typical appearance

They typically occur from the tail under the back legs, along the ventral midline to the chest and the head.

• Occult sarcoids

These are flat, hairless, lichen-like, slightly crusting, dark patches. They often have a smooth, dark hairless area around them.

• Verrucose sarcoids

These are raised, nobbly, dark areas that often spread into poorly defined margins. They can also be ulcerated on occasions.

• Nodular sarcoids

These are firm and nodular skin lumps which may have normal skin over them.

• Fibroblastic sarcoids

These are often ulcerated, weeping, raised sore lesions that may become pedunculated and cauliflower-like.

• Mixed sarcoids

Sarcoids are commonly a mixture of two or more of the forms described above.

• Malevolent sarcoids

These are rare, invasive sarcoids that invade deeper tissues beneath the skin.^[2]

Very often warts in the girth area can be mistaken for sarcoids and also match the descriptions above. Another common cause of similar pathology is dermatophytosis (fungal infection on the skin).

Diagnosis

A positive diagnosis can only be made using histopathology of a biopsy, however in most cases the location and character of the lesions is so suggestive of equine sarcoid that a diagnosis can be made and a biopsy may be contraindicated as it can awaken an otherwise slow growing lesion^[3].

Treatment

Treatments may include banding with rubber rings, surgical excision, cryosurgery, injection with Bacillus Calmette-Guérin as an immunomodulator, radioactivity^[4] and topical or injected chemotherapy agents. No one treatment is suitable for all sarcoids and it is essential that individual cases are assessed by a veterinarian to ensure that the best treatment is selected. Sarcoids can be difficult to treat and this has encouraged many bogus treatments to be put forward.

Prognosis

It is occasionally possible to successfully remove all of a horse's sarcoids but in many cases the treatment results in control rather than resolution of the lesions.

References

1. ^ Chambers G, Ellsmore VA, O'Brien PM et al. Association of bovine papillomavirus with the equine sarcoid. J Gen Virol (2003) 84:1055-1062
2. ^ Knottenwelt, DC, Proceedings of the 9th SIVE Congress, 2003 [1]
3. ^ A Martens, A de Moor, R Ducatelle. PCR detection of Bovine Papilloma Virus DNA in superficial swabs and scrapings from equine sarcoids.The Veterinary Journal (2001) 161, 280-286.
4. ^ Michael Walker DVM, William Adams DVM, James Hoskinson DVM, J.P. Held DMV, James Blackford DVM, Dennis Geiser DVM, Dallas Goble DVM, John Henton DVM (1991) IRIDIUM-192 BRACHYTHERAPY FOR EQUINE SARCOID, ONE AND TWO YEAR REMISSION RATES Veterinary Radiology & Ultrasound 32 (4), 206–208.