ISSN 2398-2969      

Otitis media/interna

Clapis

Synonym(s): Middle/inner ear infection, Labyrinthitis, Otitis labyrinthica


Introduction

  • Cause: bacterial infection of the inner and middle ear.
  • Signs: peripheral vestibular signs.
  • Diagnosis: imaging (radiography, ultrasonography, CT scan, MRI).
  • Treatment: surgery.
  • Prognosis: guarded.
  • Otitis media and otitis interna are terms that refer to inflammation of the middle and inner ear, respectively .
  • Otitis media and otitis interna are commonly referred to one single pathology. While they have a lot in common, there are some differences:
    • Otitis media is easier to visualize with diagnostic imaging, but does not produce peripheral vestibular signs.
    • Otitis interna more difficult to visualize with diagnostic imaging, but produces peripheral vestibular signs due to labyrinthitis.
    • Otitis interna without otitis media may occur.
    • Otitis media without otitis interna may be common, as many rabbits with detected changes in the middle ear are asymptomatic.
  • In rabbits, these conditions are most commonly associated with bacterial infection.
  • Disease may be unilateral or bilateral, but often bilateral.
  • Otitis media and otitis interna often occur concurrently; subclinical otitis media may have prevalence of 10-30% in rabbits.
  • Otitis externa is correlated with otitis media/interna.
  • Prevalence of CT changes in middle/inner ear in rabbits with vestibular signs is 55%. The rest of rabbits with vestibular disease may be false-negative results, otitis interna without otitis media, encephalitozoonosis or other conditions.
  • Rabbits that are housed in or originate from large breeding colonies, commercial units or rescue centers that report outbreaks of respiratory disease are thought to be at higher risk.
  • The association of otitis media/interna with respiratory disease is controversial.
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Presenting signs

  • Clinical signs vary from none (asymptomatic cases) to severe neurological disturbance depending on the nature and severity of the disease and the anatomic structures involved.
  • The onset of signs may be acute or chronic/progressive.
  • Rabbits with otitis media (without otitis interna) may present with non-specific clinical signs, eg lethargy, inappetence, and/or pain or pruritis associated with the base of the ear Ear: otitis - purulent 01 Ear: otitis - purulent 02.
  • Facial paralysis may occur and can be unilateral Face: nerve paralysis 03 - unilateralor bilateral. Unilateral facial paralysis is more common. Facial paralysis is seen as contraction of the affected side .
  • Purulent material may be present in the external ear if the tympanic membrane has ruptured Ear: otitis - purulent 01 Ear: otitis - purulent 02or if otitis externa is associated (and maybe the initial cause) with otitis media/interna.
  • Otitis interna is a common cause of peripheral vestibular disease in rabbits and affected animals usually present with neurological signs, including head tilt Head tilt Head tilt: otitis media, rolling, ataxia and/or nystagmus.

Geographic incidence

  • Disease incidence does not appear to be related to geographic location.
  • Countries where lop rabbits are more popular, eg UK, may have increased prevalence.

Sex predisposition

  • No sex predisposition detected.

Breed predisposition

  • Lop eared rabbits have a much higher incidence of otitis media secondary to otitis externa .
  • Lop eared rabbits are predisposed to otitis externa due to the abnormal conformation of the external ear canal and the poor ventilation inside the ear; this can lead secondarily to otitis media/interna.

Age predisposition

  • It can occur at any age.
  • There are no reported age or sex predispositions associated with otitis media/interna. Due to chronicity and slow progression of otitis media in some cases, clinical disease may be more prevalent in older rabbits.

Cost considerations

  • Variable, but generally moderate to expensive. Definitive diagnosis, particularly if CT or MRI are used, is expensive. Surgical treatment, many times involving both ears in two separate surgical events, is expensive.
  • Rabbits with clinical disease affecting one ear may be more predisposed to develop the same problem in the other ear.
  • In early cases with mild clinical signs, empirical treatment is generally inexpensive.
  • Most cases are chronic in nature by the time of presentation/diagnosis, therefore long courses of medication and frequent revisit appointments may be required. 

Special risks

  • To prevent traumatic injuries, rabbits with torticollis Head tilt due to otitis interna must be handled carefully, as they tend to roll uncontrollably when stressed.
  • Surgery is very aggressive and has some associated risks: facial nerve paralysis, lack of improvement or even worsening of clinical signs.

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.
  • de Matos R, Ruby J, Van Hatten R A et al (2015) Computed tomographic features of clinical and subclinical middle ear disease in domestic rabbits (Oryctolagus cuniculus): 88 cases (2007-2014). J Am Vet Med Assoc 246 (3), 336-343 PubMed.
  • King A M, Posthumus J, Hammond G et al (2012) Comparison of ultrasonography, radiography and a single computed tomography slice for the identification of fluid within the tympanic bulla of rabbit cadavers. The Vet J 193 (2), 493-497 PubMed.
  • Porfida-Ferreira T S, Felizardo M R, Sena de Gobbi D D et al (2012) Virulence genes and antimicrobial resistance profiles of Pasteurella multocida strains isolated from rabbits in Brazil. Sci World J 2012, 685028 PubMed.
  • Hammond G, Sullivan M, Posthumus J et al (2010) Assessment of three radiographic projections for detection of fluid in the rabbit tympanic bulla. Vet Radiol Ultrasound 51 (1), 48-51 PubMed.
  • Okewole E A & Olubunmi P A (2008) Antibiograms of pathogenic bacteria isolated from laboratory rabbits in Ibadan, Nigeria. Lab Anim 42 (4), 511-514 PubMed.
  • King A M, Hall J, Cranfield F et al (2007) Anatomy and ultrasonographic appearance of the tympanic bulla and associated structures in the rabbit. The Vet J 173 (3), 512-521 PubMed.
  • Lee J, Eom K, Seong Y et al (2006) Ultrasonographic evaluation of the external ear canal and tympanic membrane in dogs. Vet Radiol & Ultrasound 47 (1), 94-98 PubMed.
  • Kumar B V D, Rajashekar G & Rao P S (2000) Vestibular syndrome in a rabbit. Indian Vet J 77 (3), 268-269 VetMedResource.
  • Deeb B J, DiGiacomo B L, Bernard B L et al (1990) Pasteurella multocida and Bordetella bronchiseptica infections in rabbits. J Clin Microbiol 28 (1), 70-75 PubMed.
  • Kunstyr I & Naumann S (1985) Head tilt in rabbits caused by Pasteurellosis and encephalitozoonosis. Lab Anim 19 (3), 208-213 PubMed.
  • Flatt R E, Deyoung D W & Hogle R M (1977) Suppurative otitismedia in the rabbit: prevalence, pathology and microbiology. Lab Anim Sci 27 (3), 343-347 PubMed.
  • Snyder S B, Fox J G & Soave O A (1973) Subclinical otitis media associated with Pasteurella multocida infections in New Zealand white rabbits (Oryctolagus cuniculus). Lab Anim Sci 23 (2), 270-272 PubMed.
  • Fox R R, Norberg R F & Myers D D (1971) The relationship of Pasteurella multocidato otitis media in the domestic rabbit (Oryctolagus cuniculus). Lab Anim Sci 21 (1), 45-48 PubMed.

Other sources of information

  • Raftery A (2005) Total Ear Canal Ablation and Bulla Osteotomy in the Rabbit. In: Proc Autumn 2005 British Vet Zoological Society. pp 77.
  • Deeb B J & Carpenter J W (2004) Neurologic and Musculoskeletal diseases. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. 2nd edn. Eds: Quesenberry K E & Carpenter J W. W B Saunders, St. Louis. pp 203-210.
  • Lorenz M D & Kornegay J N (2004) Oliver & Lorenzs Handbook of Veterinary Neurology. 4th edn. W B Saunders, St Louis.
  • Harcourt-Brown F (2002) Textbook of Rabbit Medicine. Butterworth Heinemann, Edinburgh.
  • Percy D H & Barthold S W (2001) Pathology of Laboratory Rodents and Rabbits. 2nd edn. Iowa State University Press, Ames.
  • Radlinsky M G & Mason D E (2000) Diseases of the Ear. In: Textbook of Veterinary Internal Medicine. 6th edn. Eds: Ettinger S J & Feldman E C. Elsevier Saunders, St Louis. pp 1168-1186.

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