Mouth: ulcers in Horses (Equis) | Vetlexicon
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Mouth: ulcers

ISSN 2398-2977

Contributor(s) :

Synonym(s): Oral ulceration, stomatitis, vesicles


  • Disruptions in the integrity of the oral mucosa.
  • Cause: infectious, toxic, caustic, traumatic, neoplasia. 
  • Signs: ptyalism, inappetence/anorexia, visible ulcers/vesicles/bullae/crusts.
  • Diagnosis: physical and oral examination, other procedures dependent on inciting cause.
  • Treatment: dependent on inciting cause.
  • Prognosis: dependent on inciting cause.

Presenting signs

  • May be preceded by vesicles, crusts or bullae.
  • Variable depending on inciting cause.
  • Excessive salivation   Mouth: hypersalivation - saliva froth  .
  • Inappetence/anorexia.
  • Depression.

Geographic incidence

  • None.

Age predisposition

  • Any age.

Breed/Species predisposition

  •  None.

Public health considerations

Cost considerations

  • Dependent on inciting cause.

Special risks

  • Dependent on inciting cause.




  • Variable, depending on inciting cause.


  • Virus invades mucosal epithelium producing vesicles which rupture to leave ulcers.

Phenylbutazone  Phenylbutazone 

  • Inhibits prostaglandin synthesis    →   ?vasoconstriction of microvasculature of GI mucosa    →   ischemia    →   ulcer formation.


  • ?interference with mitochondrial oxidative enzymes    →   cell membrane damage    →   acantholysis + vesicle formation    →   ulcers.


  • Direct action of the chemical on the oral mucosa    →   chemical burn    →   mucosal slough    →   ulceration.

Food impaction

  • Can   →   infected food material    →   infected + abrased oral mucosa    →    ulceration.

Direct trauma

  • Can   →    abrasion and ulceration.
  • Excessively long or broken teeth   Teeth: fracture  .
  • Sharp foreign bodies in feedstuff.


  • Dependent on inciting cause.


  • Cases with viral causes may be part of a contagious epidemic, eg vesicular stomatitis   Vesicular stomatitis  .
  • Chemical/toxin induced ulcers may affect several animals in the same paddock, eg contaminated water trough, infested grazing.


Presenting problems

  • Excessive salivation (ptyalism   Mouth: ptyalism  ).
  • Inappetence/anorexia.
  • Weight loss   Weight loss: overview  .
  • Visible ulcers/vesicles/bullae/crusts   Mouth: trauma - wallpaper paste toxicity    Mouth: ulceration - pituitary adenoma  .
  • Halitosis.
  • Depression.

Client history

  • Variable depending on inciting cause.
  • History of toxin/drug ingestion.
  • Viral outbreak in in-contacts.
  • Other signs of inciting disease process.

Clinical signs

  • Ptyalism   Mouth: ptyalism  .
  • Variable anorexia.
  • Dysphagia.
  • Visible ulcers/vesicles/bullae affecting oral mucosa.
  • Various others specific to inciting cause.
  • Depression.
  • Fever.
  • Synchronous diaphragmatic flutter (hypocalcemia due to blister beetle).

Diagnostic investigation

Confirmation of diagnosis

Discriminatory diagnostic features

  • Various depending on inciting cause.

Hematology and biochemistry

  • May help in identification of inciting cause.

Radiography  Head: radiography 

  • May help in identifying dental aberrations/disease.

Serology  Serology 

  • Acute and convalescent sera for VS and EHV.


  • Virus isolation from vesicle fluid.


  • Examine forage/pasture, Blister beetles, foreign bodies or toxic plant matter.
  • Test stomach contents for toxin, eg cantharidin.
  • Tissue biopsy   Biopsy: overview  .
  • Biopsy of ulcerated tissue and histology may help to rule out neoplasia.

Definitive diagnostic features

  • Variable, depending on inciting cause.

Gross autopsy findings

  • Variable, depending on inciting cause.

Histopathology findings

  • Variable, depending on inciting cause.

Differential diagnosis


Initial symptomatic treatment

  • Physically remove inciting cause, eg toxin/chemical source, forage, foreign body.
  • Stop implicated drug therapy.
  • Move from affected environment, eg infested paddock.
  • Treat dental disease   Teeth: dental disease - overview  .
  • Topical therapy to ameliorate symptoms of pain and irritation, eg mouthwashes:

Either2% potassium permanganate.
OR 0.5% hydrogen peroxide   Hydrogen peroxide  .
OR Saturated boric acid solution.
OR1% v/v povidone-iodine solution   Povidone-iodine  .

Standard treatment

  • Dependent on inciting cause - treat primary disease process.


  • Dependent on inciting cause.
  • Suspected cases of VS and EHV should be quarantined until definitive diagnostic test results area available to determine further action.

Subsequent management


  • Dependent on inciting cause.
  • Dependent on inciting cause.


  • Dependent on inciting cause.



  • Dependent on inciting cause.


  • Dependent on inciting cause.

Group eradication

  • Dependent on inciting cause.



  • Dependent on inciting cause.

Expected response to treatment

  • Dependent on inciting cause.

Reasons for treatment failure

  • Dependent on inciting cause.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Johnson P J et al (2012) Ulcerative glossitis and gingivitis associated with foxtail grass awn irritation in two horses. Equine Vet Educ 24 (4), 182-186 VetMedResource.

Other sources of information

  • Mair T, Divers T & Ducharme N (2002) Manual of Equine Gastroenterology. W B Saunders.
  • Brown C M & Bertone J J (2002) The 5-Minute Veterinary Consult Equine. Lippincott, Williams & Wilkins.