DISEASE SUMMARY PAGE

Bacterial Otitis Media / Interna in Lagomorphs

Flushing the ear of a rabit with otitis media. Click here for full page view with caption Endoscopic examination of a rabbit's ear. Click here for full page view with caption Head tilt due to pasteurellosis. Click here for full page view with caption

Summary Information
Diseases / List of Bacterial Diseases / Disease summary
Alternative Names --
Disease Agents
  • Pasteurella multocida (see: Pasteurellosis in Lagomorphs) (B601.11.w11, B602.20.w20, B603.3.w3, B606.13.w13, B614.8.w8, J495.21.w1, J495.23.w, J495.27.w1)
    • Pasteurella multocida and Bordetella bronchiseptica are the most common organisms involved in otitis media/otitis interna. (B603.3.w3)
    • In one study, Pasteurella multocida was reported to be isolated from 97% of cases of otitis media, including both clinical and subclinical cases. Bordetella bronchiseptica and staphylococci were also found in five to ten percent of cases. (J495.21.w1)
  • Other bacteria (B602.20.w20) including Staphylococcus aureus, Staphylococcus  spp., Pseudomonas aeruginosa, Pseudomonas sp., Bordatella bronchiseptica, Bacteroides sp. Proteus mirabilis and Escherichia coli. (J15.28.w1, J60.6.w2)
  • Escherichia coli (B601.11.w11, B603.3.w3)
  • Proteus mirabilis (B601.11.w11, B603.3.w3)
  • Pseudomonas aeruginosa (B601.11.w11, B603.3.w3)
  • Staphylococcus spp. (B606.13.w13)
    • Staphylococcus aureus (B601.11.w11, B603.3.w3)
    • In pet rabbits, Staphylococcus aureus  is commonly cultured. (V.w122, V.w65)
  • Other bacteria (B602.20.w20)
  • Mycoplasma infection (B603.1.w1)

Note: bacterial infection may be secondary to:

  • Psoroptes cuniculi Infection
    • There is no evidence to suggest that ear mites are a cause of otitis media; however, affected animals may have concurrent Pasteurella multocida infection. (B614.8.w8)
    • These mites can cause an otitis externa and this infection can extend to an otitis media. (B603.1.w1)
  • Migration of a foreign body through the tympanum. (B603.1.w1)
  • Iatrogenic aural injury. (B603.1.w1)
  • Lack of normal ear drainage in lop-eared rabbits. (V.w65)
Infectious Agent(s)
Non-infectious Agent(s) --
Physical Agent(s) --
General Description Infection that originates in the middle ear can spread to:
  • The ear canal (if the tympanic membrane ruptures). (B602.17.w17, B602.20.w20)
  • The inner ear, leading to labyrinthitis, and then sometimes to the brain resulting in severe neurological signs including seizures. (B602.20.w20)
Clinical signs

Otitis media is often not clinical and is a common incidental finding at post-mortem or on radiographs. Clinical vestibular disease is often a consequence of a spread of infection from an otitis media to an otitis interna or to the brainstem. (B603.4.w4)

  • Head tilt (B602.20.w20, B606.13.w13, J15.28.w1, J60.6.w2)
    • Otitis interna is the commonest cause of head tilt. (B606.13.w13)
    • A rabbit may hold its head tilted if it has middle or outer ear pain. (B603.1.w1)
    • The down-tilted eye may have corneal oedema and ulceration. (J60.6.w2)
    • Note: if the condition is bilateral, head tilt may not be present. (V.w65)
      • In these cases, there may be no obvious signs but the rabbit is described by the owner as "not doing right". (V.w65)
      • The presence of a head tilt does not mean the condition is not bilateral, as one side may be worse and the head tilted reflecting this. (V.w65)
  • Soft tissue swelling at the base of the ear canal can sometimes be seen in cases of severe otitis media where there is a build up of pus within the ear. (B602.20.w20)
  • Pus in the ear canal may be seen if the tympanic membrane has ruptured (B606.13.w13) or if there is an otitis externa. (V.w65)
  • Facial paralysis or Horner's syndrome - lip, eyelid and ear drooping may simulate a head tilt appearance. (B603.1.w1)
  • Deafness: but this is very difficult to ascertain in rabbits. (B603.1.w1)
  • Signs of pain and the rabbit is described by the owner as "not doing right". (V.w65)
    • These may be the only indications of the disease if it is bilateral. (V.w65)
  • Nystagmus (horizontal). (J60.6.w2)
    • With peripheral disease, nystagmus is horizontal or rotary, does not change direction if the head position is changed, and has the fast phase in the direction of the lesion. (B601.11.w11, J15.28.w1)
  • Torticollis, nystagmus and ataxia. (B602.17.w17)
  • Loss of balance may result in the rabbit continuously rolling and spinning. (J60.6.w2)
  • Excessive scratching at the ear base may be noted. (B602.17.w17)
Clinical pathology
Further Information
  • Peripheral vestibular disease is usually due to otitis interna; most commonly this occurs subsequent to spread of infection from a chronic otitis media. (B603.3.w3)
  • Primary otitis media can occur by spread of infection from the upper respiratory tract to the middle ear via the Eustachian tubes. A concurrent rhinitis or sinusitis is suggestive of this. (B601.11.w11, B603.3.w3)
  • Infection in the middle ear can then spread to:
    • The ear canal (if the tympanic membrane ruptures) (B602.20.w20)
    • The inner ear, leading to labyrinthitis and then sometimes to the brain resulting in severe neurological signs including seizures. (B602.20.w20)
Susceptibility
  • Lop-eared breeds are more susceptible; in many of these rabbits, the fold in the ear cartilage is such that the lumen is entirely closed off leading to no drainage at all of cerumen from the ear. (V.w65)
Diagnosis
  • Clinical signs such as head tilt, an ear base abscess, or excessive scratching at the ear base without parasites being present. (B602.17.w17, J15.28.w1)
    • It is also useful to identify whether there is a primary or secondary otitis externa, or a ruptured tympanic membrane. (B601.11.w11)
      • The ear canal may contain pus. (J60.6.w2)
      • If the tympanic membrane rupture has occurred, dried exudate may be found crusting in the ear canal and white purulent exudate (for Pasteurella multocida infection) under this. (B602.17.w17)
      • Gentle pressure at the ear base may express the exudate. (B602.17.w17)
  • Skull radiography (B601.11.w11, B602.17.w17, B602.20.w20, B606.13.w13, J15.28.w1)
  • In the tympanic bulla, increased soft tissue density (exudate) and thickening of the bone. (B602.17.w17, J60.6.w2)
  • Positive contrast may be used in the ear; this will show if the tympanic membrane is intact. (V.w65)
  • Endoscopy with a rigid endoscope may be used to examine the ear down to the tympanic membrane. (B602.36.w36, J513.2.w2, P6.3.w1, V.w65) See: Imaging in Lagomorph Diagnosis and Treatment
  • Culture and sensitivity
    • Aural swabs or deep nasal swabs. (B601.11.w11)
  • CT scanning if available. (B601.11.w11)
  • Histology (Diagnosis of associated encephalitis). (B602.20.w20)
  • See: 
Differential diagnoses of head tilt include:
Treatment
  • Long term systemic antibiotic treatment is needed - often four to six weeks or longer. (B601.11.w11, B602.20.w20, B606.13.w13, J15.28.w1)
  • Topical antibiotics
    • If the tympanic membrane is ruptured: 
      • topical 0.3% gentamicin (B602.20.w20) Note: this should be used with care due to the potential of neurotoxicity. (V.w65)
      • or 0.5% enrofloxacin / 1.0 % silver sulfadiazine otic solution. (B602.20.w20)
  • Flushing the ear canal
    • In cases of severe disease/otitis externa, the patient should be anaesthetised and the ear canal gently flushed with warm saline solution. (B601.11.w11, B602.20.w20)
    • Use a small 3 1/2 -F red rubber catheter. (B602.20.w20)
    • NB: avoid flushing when the tympanic membrane is ruptured. (B602.20.w20)
  • Ear wick
  • Bulla osteotomy
    • This technique can be used in cases of severe otitis media that are not responding to medical treatment. However, there is a high risk of postoperative complications e.g., cellulitis, abscessation, and facial nerve paralysis. Complications can be reduced by using doxycycline gel or antibiotic-impregnated polymethylmethacrylate beads (see: Production of Antibiotic-Impregnated Beads) placed in the tympanic bulla, along with long term systemic antibiotics. (B601.11.w11, J15.28.w1)
    • Neck muscle spasms are common and the rabbit's neck should be massaged regularly. (B601.11.w11)
    • See: Bulla Osteotomy in Rabbits (Techniques)
  • Symptomatic treatment for torticollis:
    • Consider short-acting corticosteroid (e.g. Dexamethasone sodium phosphate, 0.5 - 2.0 mg/kg subcutaneously to limit inflammation. (J60.6.w2)
    • Supportive care, including feeding if necessary. (J60.6.w2)
    • Note: minimise handling, as loss of balance when the rabbit is picked up may cause it to twist frantically. (J60.6.w2)
    • Anti-emetic drugs
      • These can be useful for preventing suspected nausea that may occur secondary to vestibular damage.
      • Metoclopramide: 0.5 mg/kg orally or via subcutaneous injection every eight hours. (B601.11.w11, J15.28.w1)
      • Antihistamines and phenothiazine derivatives can prove useful in patients with a head tilt because these drugs act on the vestibular pathways. (B601.11.w11, J15.28.w1)
        • Procloperazine (Phenothiazine derivative) : 0.25 mg/kg orally every eight to twelve hours (this dose has been extrapolated from human medicine). (B601.11.w11)
        • Meclizine: 6.25 to 12.5 mg per rabbit orally every eight hours (this comes from anecdotal reports in the USA). (B601.11.w11)
    • Appropriate antibiotic ophthalmic ointment as required for the down-tilted eye. (J60.6.w2)
    • In the longer term, anti-inflammatory treatment such as NSAIDs, cyclosporins or corticosteroids may be considered. (V.w65)
    • Note:
      • Rabbits with milder signs of torticollis often compensate well and live a normal life except for the changed posture. (J60.6.w2)
      • Euthanasia is appropriate for severe torticollis cases with complete loss of balance. (J60.6.w2)
Associated Techniques
Host taxa groups /species
Disease Author Nikki Fox BVSc MRCVS (V.w103); Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referees John Chitty BVetMed CertZooMed MRCVS (V.w65)

Return to top of page