The pathogenesis is often multifactorial involving several predisposing factors. Ear conformation is the most frequently encountered of these in veterinary consulting rooms, with the lop-eared breeds being overrepresented.
Clinical signs of ear disease
- Ear scratching
- Head shaking
- Gut stasis
- Vestibular signs (head tilt, torticollis, nystagmus, ataxia, circling)
Signs of rabbit ear infection can be non-specific and will vary depending on location of the disease.
- Otitis externa
Otitis externa is commonly caused by Psoroptes cuniculi and affected rabbits will be intensely pruritic with a characteristic crusty exudate in the ear canal, extending onto the pinna.
- Otitis media
Rabbits with middle ear infection (otitis media) will tend to exhibit clinical signs associated with pain such as lethargy, inappetence and gut stasis, although some cases can be subclinical. Pasteurella multocida is the infectious agent most commonly involved.
- Otitis interna
Otitis interna frequently occurs as an extension of otitis media and affected rabbits will typically show vestibular signs, so a rabbit ear infection with a head tilt will usually suggest inner ear involvement. Progression to other neurological signs including facial nerve paralysis and Horner’s syndrome may occur.
Predisposing factors: the lop ear rabbit
The lop-eared rabbit breeds have altered ear anatomy due to years of selective breeding. Their vertical canals have a fold to enable the lop-eared look and tend to be stenotic. This abnormal conformation predisposes them to cerumen build-up in their ear canals and ear disease. Regular routine ear cleaning with a product safe for use in rabbits can help to reduce this cerumen build up and should be considered in all lop breeds.
A thorough history and clinical examination including otoscopy is needed to reach a diagnosis and formulate a treatment plan. Otoscopy can present a challenge in our rabbit patients; it is difficult in most conscious rabbits and almost impossible in lops and a thorough otoscopic examination will often require sedation or general anaesthesia. If a complete examination of the ear canal is not possible with an otoscope, endoscopy or advanced imaging can be considered. Flushing the ear with a cleaner that is safe to use in rabbits will aid in visualising the ear canal.
How to treat rabbit ear infections
Treatment of rabbit ear infections is dependent on the underlying cause.
Treatment of otitis externa
Otitis externa is often caused by the rabbit ear mite, Psoroptes cuniculi. It is best to leave the thick crust that forms in an affected ear, not only is removal painful but it is usually unnecessary. Rabbits should be treated with a licensed product containing ivermectin.
Treatment of otitis media and otitis interna
The treatment of rabbit inner and middle ear infections is broadly similar as the two diseases are usually closely linked. Difficulty arises in many cases because treatment options are limited by the lack of licensed products available.
- Ear flushing
Flushing the ear under sedation or general anaesthesia will remove cerumen and remove or at least dilute any infectious agents. Due to the difficulties in fully visualising the rabbit ear canal, it can be tricky to identify the tympanic membrane and often not possible to confirm (or rule out) rupture. It is best to assume that the tympanic membrane is ruptured and formulate a treatment plan accordingly. Saline can be used for flushing or an ear cleaner that is safe for use in rabbits.
- Systemic treatment
Systemic antibiotics should be used if appropriate based on bacteriology and sensitivity testing.
- Topical antibiotics
Ear preparations containing antibiotics should be avoided in most cases for several reasons:
- Lack of licensed products – most topical preparations are based on canine otitis treatment.
- Polypharmacy – risk of side effects, especially with preparations containing steroids.
- Ototoxicity – the tympanic membrane is frequently ruptured so topical antibiotics risk ototoxicity.
A rabbit with an ear infection can become unwell quite quickly so prompt and effective treatment is essential. Owners of rabbits with underlying breed predisposition to ear disease such as lops, should be encouraged to monitor ear health closely and where appropriate the regular routine use of a rabbit-safe ear cleaner should be encouraged.