Equis ISSN 2398-2977

Papillomatosis

Synonym(s): Warts, equine viral papillomatosis, grass warts, milk warts, fungal plaques, cutaneous viral papilloma, Angleberry

Contributor(s): Clare Knottenbelt, Prof Derek Knottenbelt, Rosanna Marsella, Reginald Pascoe, Sue Paterson, David Senter

Introduction

  • Congenital form occurs in newborn foals; usually single or few but can be extensive.
  • Viral papilloma is very common in young horses and less so in older animals. Most cases occur in young weanlings or yearlings during their first season at grass, hence colloquial terms - Grass warts, milk warts.
  • Spontaneous remission is common but NOT invariable.  
  • Several different syndromes may relate to different variants of the virus or to different related and unrelated viruses. Aural plaques (pinnal acanthosis) is a common but poorly understood variant that is probably caused by a different virus and transmitted by the biting flies and especiallySimuliumspp (Black Fly).  
  • Initial development in older horses is much less inclined to spontaneous remission.
  • There is no relationship in any form to the equine sarcoid   Sarcoid  . Immune response to viral papilloma is not protective or curative for sarcoid.
  • Cause: equine papilloma virus.
  • Signs: small, multiple grey pedunculated lesions on muzzle, head and ears.
  • Diagnosis: history, clinical signs, biopsy.
  • Treatment: not usually necessary; excision if causing interference, eg with eating.
  • Prognosis: depends on type.

Pathogenesis

Etiology

  • Equine papilloma virus is implicated.  
  • Usually require some form of skin damage to infect the skin.

Predisposing factors

General
  • Age-related occurrence and implications for treatment and prognosis.

Pinnal acanthosis is a very difficult condition that should not be treated.

Timecourse

  • Onset over 24 weeks with some resolving lesions and some new lesions at first than gradually spontaneous resolution of the typical papilloma.
  • Atypical papilloma occurs in older horses, especially in the groin region. 
  • Pinnal acanthosis is a long-standing condition; most cases remain static for years and sometimes for life.

Epidemiology

  • Young horses on pastures with a history of being grazed by affected yearlings.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Barrelet A, Foote A & Littlewood J D (2010)Common equine skin tumours.UK Vet15(6), 9-17 VetMedResource.
  • van den Top J G B, de Heer N, Klein W R & Ensink J M (2008)Penile and preputial tumours in the horse: A retrospective study of 114 affected horses.Equine Vet J40(6), 528-532 PubMed.
  • Pilsworth R C & Knottenbelt D (2007)Papillomatosis (viral warts).Equine Vet Educ19(8), 444-446 VetMedResource.

Other sources of information

  • Pascoe R R & Knottenbelt D C (1999) Manual of Equine Dermatology. W B Saunders, London.
  • Scott D W (2003)Neoplastic and Non-neoplastic Tumors.In:Equine Dermatology.W B Saunders, Philadelphia, USA. pp 700706.


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