 Viral particles are not produced during infection of other species and, unlike in tumours associated with human papillomavirus, the viral DNA is not integrated into the host genome.Equine sarcoid, a naturally occurring skin tumour affecting horses, donkeys and mules, is associated with strains of BPV-1/2 which may be equine specific.The lesions can occur anywhere on the body, often multiply, with the limbs, thorax–abdomen, head and paragenital areas being particularly commonly affected.