Equis ISSN 2398-2977

Ear: otitis externa / otitis media

Contributor(s): Rosanna Marsella, David Senter

Introduction

  • diseases of the external ear canal (otitits externa) of the horse are not as common as in small animals.
  • Cause: several diseases, however, can cause ear disease.
  • Primary causes of otitis include atopic dermatitis   Skin: atopy  , black fly bites, insect hypersensitivity, egCulicoides  Insect hypersensitivity  , and ticks. Less commonly food allergy   Skin: food hypersensitivity  , Psoporptic mange   Psoroptic mange  and vasculitis   Vasculitis  have been reported to induce ear disease. 
  • Otitis externa secondary to otitis media has also been reported in horses and appears to have an insidious course.
  • Signs: exudate, crusting, pruritus, ear rubbing, head tossing/weaving.
  • Diagnosis: cytological examination of exudates, otoscopic exam, endoscopy. 
  • Treatment: fly control, food trials, anti-inflammatory drugs, antibiotics.
  • Prognosis: depends on underlying cause.

Pathogenesis

Etiology

  • Many different etiologies can cause ear disease.

Predisposing factors

General
  • Excessive humidity may predispose to secondary infections.

Specific

  • Allergic disease, eg atopic dermatitis   Skin: atopy  , food allergy   Skin: food hypersensitivity  , insect hypersensitivity   Insect hypersensitivity  .
  • Parasitic, eg psoroptes   Psoroptic mange  .
  • Neoplastic, eg aural plaques   Ear: pinnal acanthosis  . Aural plaques (equine ear papillomas) occur at any age in any breed of horses. They tend to be bilateral and tend to be aggravated by biting flies, especially black flies. It is thought to be viral in origin. No effective therapy has been reported and appears to be purely a cosmetic problem.
  • Headshaking   Behavior: headshaking   is a recognized syndrome and presents as uncontrollable, spontaneous, rapid and repetitive head movements without apparent cause. Although the majority of cases of headshaking in the horse are idiopathic, several different underlying diseases including otitis externa, media or interna, otic foreign bodies or ear mites need to be ruled out.
  • The importance of eliminating any definable cause by thorough examination is emphasized due to the poor prognosis for treatment of idiopathic headshaking   Behavior: headshaking  .
  • A thorough otic examination is needed to rule out aural disease.

Pathophysiology

  • Primary disease triggers inflammation which predisposes to secondary infections, eg bacteria and yeast infections.
  • Pruritus may be caused by the underlying disease and is further aggravated by the establishment of the infection.

Timecourse

  • Depends on the underlying cause.
  • Once infection is established, it needs to be addressed by both topical and systemic therapy and removal of the underlying cause is generally not sufficient.

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.
  • Rand C L et al (2012) Otitis media-interna and secondary meningitis associated with Corynebacterium pseudotuberculosis infection in a horse. Equine Vet Educ 24 (6), 271-275 VetMedResource.
  • Slovis N (2012) Equine otitis media-interna. Equine Vet Educ 24 (6), 276-278 VetMedResource.
  • Sargent S J, Frank L A, Buchanan B R, Donnell R L & Morandi F (2006) Otoscopic, cytological, and microbiological examination of the equine external ear canalVet Derm 17 (3), 175-181 PubMed.
  • Newton S A (2005) Idiopathic headshaking in horsesEquine Vet Educ 17, 83-91 VetMedResource.
  • Newton S A, Knottenbelt D C & Eldridge P R (2000) Headshaking in horses: possible etiopathogenesis suggested by the results of diagnostic tests and several treatment regimes used in 20 casesEquine Vet J 32, 208-216 PubMed.
  • Newton S A & Knottenbelt D C (1999) Vestibular disease in two horses: a case of mycotic otitis media and a case of temporohyoid osteoarthropathyVet Rec 145 (5), 142-144 PubMed.
  • Hassel D M, Schott H C II, Tucker R L & Hines M T (1995) Endoscopy of the auditory tube diverticula in four horses with otitis media/internaJAVMA 207 (8), 1081-1084 PubMed.
  • Madigan J E, Stephanie J, Valberg S J et al (1995) Muscle spasms associated with ear tick (Otobius megnini) infestations in five horsesJAVMA 207, 7476 PubMed.
  • Blythe L L, Watrous B J, Schmitz J A et al (1984) Vestibular syndrome associated with temporohyoid joint fusion and temporal bone fracture in three horsesJAVMA 185, 775-781 PubMed.
  • Power H T, Watrous B J & de Lahunta A (1983) Facial and vestibulocochlear nerve disease in six horsesJAVMA 183, 1076-1080 PubMed.
  • Montgomery T (1981) Otitis media in a ThoroughbredVet Med Small Anim Clin 76, 722-724 PubMed.

Other sources of information

  • Blythe L L (1989) Otitis media and interna in the horse. Its relationship to head tossing and skull fractures. In: Proc 7th ACVIM Annual Meeting. pp 1015-1018.


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