Lapis ISSN 2398-2969

Otitis externa

Contributor(s): Alana Shrubsole-Cockwill, Richard Saunders, David Perpinan

Introduction

  • Otitis externa is an acute or chronic inflammatory condition of the external ear.
  • It is a common presenting sign, particularly in lop-eared rabbits.
  • Cause: commonly caused by parasitic or bacterial infection.
  • Signs: self-trauma, headshaking, asymmetrical pinnae.
  • Diagnosis: otoscopic/endoscopic examination, CT.
  • Treatment: avermectins for parasitic otitis; antibiotics, ear flush and/or surgery for bacterial infections.
  • Prognosis: good to fair in mild cases; guarded to poor when there is concurrent otitis interna. Bacterial external otitis can become chronic and recurrent.

Print off the Owner factsheet on Ear canker to give to your clients.

Clinical tip
Question
: What are the best treatment options for otitis externa?
Answer: Avermectins for parasitic otitis, eg ivermectin; mild bacterial cases can be treated with topical ear cleaners + antibiotics + anti-inflammatories; lavage/flush of middle ear with sterile saline if there is significant pus/secretion in the ear canal; more severe bacterial cases may require surgery (bulla osteotomy).

Presenting signs

  • Scratching at affected ear(s) with alopecia and excoriations.
  • Headshaking.
  • Crusting of the medial pinna in psoroptic mange.
  • Foul smell to affected ear(s).
  • Resentment of handling around ear(s) Ear mites: pinch test video.
  • Inappetance, weight loss, lethargy and reduced movement can be seen if condition is severe.
  • Dropped affected ear, with the unaffected one in normal upright position .
  • Horner's syndrome .
  • Vestibular signs when the otitis externa is also associated with otitis interna Otitis media/interna.
  • Rarely dental (cheek teeth) overgrowth Dental malocclusion/overgrowth can be associated to pain when chewing due to otitis.
  • Hearing loss (difficult to evaluate).

Acute presentation

  • Head tilt Head tilt: bacterial otitis externa is commonly a chronic condition that may progress into otitis media/interna; while clinical signs of otitis externa are generally chronic, clinical signs of otitis interna may be acute, eg vestibular signs.
  • Self-trauma Self-mutilation to affected area.

Geographic incidence

  • None known, however those countries where lop-eared rabbits are more common may have a higher incidence of bacterial otitis externa.

Age predisposition

  • While otitis externa can occur at any age, chronic bacterial cases are more likely to be detected in adult rabbits.
  • Young rabbits have higher predisposition than adults for psoroptic mange.

Breed predisposition

  • Lop breeds English Lop have abnormally-shgaped ear canals (narrower and with a flexion); together with reduced ventilation of the ear canal due to dropped ears, they are predisposed to otitis externa.

Cost considerations

  • Diagnosis and treatment is relatively inexpensive for parasitic cases.
  • Diagnosis and treatment of bacterial cases may become relatively expensive or very expensive, due to chronicity, recurrence and high cost of diagnostic and surgical techniques in case of concurrent otitis interna.

Special risks, eg anesthetic

  • Anesthesia Anesthesia: general may be required for evaluation and treatment.
  • Rabbits with otitis externa secondary to otitis media Otitis media/interna may also have underlying respiratory tract infections. However, studies have pointed out that this may not be a frequent situation (it is more commonly otitis externa progressing into otitis media/interna).

Pathogenesis

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Diagnosis

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Treatment

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Prevention

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Sequelae

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mancinelli E & Lennox A M (2017) Management of otitis in rabbits. J Exotic Pet Med 26 (1), 63-73 VetMedResource.

  • dos Santos R R, Coelho C N, Nunes T A P et al (2017) Efficacy of oral doramectin as treatment for Psoroptes ovis and Leporacarus gibbus in naturally infested rabbits. Pesquisa Veterinaria Brasileira 37 (1), 47-51 VetMedResource.

  • Shang X, Wang Y, Zhou X et al (2016) Acaridical activity of oregano oil and its major component, carvacrol, thymol and p-cymene against Psoroptes cuniculi in vitro and in vivo. Vet Parasitol 226, 93-96 PubMed.

  • Budgeon C, Mans C, Chamberlin T et al (2014) Diagnosis and surgical treatment of a malignant trichoepithelioma of the ear canal in a pet rabbit (Oryctolagus cuniculus). J Am Vet Med Assoc 245 (2), 227-231 PubMed.

  • Snook T S, White S D, Hawkins M G et al (2013) Skin diseases in pet rabbits: a retrospective study of 334 cases seen at the University of California at Davis, USA (1984-2004). Vet Derm 24 (6), 613-617, e148 PubMed.

  • McTier T L, Hair A, Walstrom D J et al (2003) Efficacy and safety of topical administration of selamectin for treatment of ear mite infestation in rabbits. JAVMA 223 (3), 322-324 PubMed.

  • Cutler S L (1998) Ectopic Psoroptes cuniculi infestation in a pet rabbit. JSAP 39 (2), 86-87 PubMed.

  • Pandey V S (1989) Effect of ivermectin on the ear mange mite, Psoroptes cuniculi, of rabbits. Br Vet J 145 (1), 54-56 PubMed.

Other sources of information

  • Kelleher S (2006) Lateral Ear Canal Resections for the management of Otitis in Rabbits. In: Proc BVZS.
  • Oglesbee B L (2006) The 5 minute Veterinary Consult: Ferret and Rabbit. Blackwell Publishing. 
  • Raftery A & Chitty J (2006) An Overview of Rabbit Otitis: Its more than just Psoroptes. In: Proc BVZS.
  • Harcourt-Brown F (2002) Textbook of Rabbit Medicine. Elsevier Science.


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