here - Australian College of Veterinary Scientists

Introduction
The equine sarcoid: an update
Reg Pascoe
A locally aggressive fibroblastic tumour which is probably the most common
cutaneous tumour found in horses. Prevalent in horses aged between 1-6
years.(Torrentegui & Reid 1994: Pascoe & Knottenbelt 1999) The lesions are
frequently not life threatening but they can severely limit the use of the horse and
reduce its sale prospects, however euthanasia is not uncommon due to the
prolonged nature of treatment, likelihood of recrudescence of the problem and cost
The role of a virus, in particular Bovine papillomavirus (BPV), in its cause and
transmission is still uncertain Population and family studies have shown an
association between sarcoid susceptibility and MHC class II alleles (Lazary et al.,
1985, 1994)
Some research indicated there were no mutations of the somatic tumour suppressor
p53 gene in either horses or donkeys associated with the development of sarcoids
More recently somatic p53 gene mutations have been found to be associated with
the development of some sarcoid tumours in donkeys (Nasir et al 1999). BPV-DNA
was detected in 88% and 91% of the successful swabs and scrapings from sarcoids
respectively. The overall diagnostic sensitivity of the technique was significantly
lower compared to the clinical diagnosis of sarcoids and is unsuitable for occult
sarcoids. However, the detection of BPV-DNA in all samples obtained from
sarcoids with an ulcerated surface opens new perspectives for the detection of
sarcoid involvement in wounds or recurrence after sarcoid removal.(Martens et al
2001)
In a further study BPV DNA was detected in essentially all sarcoids examined
(96/98) it was also detected in normal skin samples from the horses with sarcoids
suggesting the possibility of a latent viral phase. Viral latency may be one explanation
of the high rate of recurrence following surgical removal. All tissues from healthy
horses with non sarcoid neoplasms or papilloma were negative to BVP DNA ( Carr
et al 2001)
Lesions occur in locations which are prone to injury and some have a history of
previous skin wounds. There is also strong presumptive evidence that sarcoids can
be transmitted by biting and domestic flies which feed on sarcoid tissue and then
browse on other horses with open sores, wounds or tumours. The introduction of a
ACVSC Proceedings Dermatology Chapter Science Week 2005 67