Ear disease is one of the most common problems encountered in rabbits yet remains seriously underdiagnosed – particularly in lop-eared breeds, which are especially vulnerable.
Ensuring that owners and breeders of lop breed rabbits are all aware of this breed’s predilection for ear disease is essential. This means any potential rabbit owners can be educated about disease prevalence in the breed and ensure they have their rabbit insured to cover the costs of treating such a condition. Being aware of this disease will also prompt regular veterinary checks to specifically look for this difficult to diagnose disease.
It is likely lopped rabbits develop the ear pathology because of the bent ear conformation trapping wax in the lower canal, causing inflammation and infection. Excessive amounts of wax build up and migrate through a ‘path of least resistance’, often out of the canal and under the skin at the bend of the ear.
This can sometimes be palpated as a swelling of the ear base but if wax instead travels down through the ear drum into deeper structures of the middle ear there can be a painful abscess but no visible clinical signs.
Unlike cats and dogs, rabbits are rarely seen scratching their ears or shaking their head, even when suffering from a painful ear condition, and so owners may be oblivious to their pet’s suffering.
The caseous or solid nature of rabbit pus means infections can become expansive and rupture the tympanic bulla, which is a bony shell attached to the skull. This is not easily palpable on physical examination and, as rabbits are extremely good at hiding pain, severe and painful ear disease can remain undetected.
Some rabbits develop a head tilt or facial asymmetry (see photo) as the first sign of an ear infection, as a result of facial nerve damage. This leads to contracture of the facial muscles of the affected side, where muscles tighten or shorten. By that stage the problem is, unfortunately, quite advanced.
Computed Tomography (CT) is the most effective way to diagnose and determine the extent of ear pathology in rabbits. We have found that a lot of ear disease in the species is diagnosed when CT scans are performed for other reasons. In a retrospective study at the RVCwe found that 26% of rabbits having CT turned out to have ear disease and 45.5% of those diagnosed with otitis media were not being scanned for ear problems specifically.
Management of the condition
Management can be medical or surgical depending on severity of the condition but, as the disease is more likely to be picked up when it is more advanced, surgery is the most common intervention. Surgery involves the removal of large sections of diseased ear canal, infected bone and pus and wax to reduce pain and suffering in rabbits who have already lost hearing. One of the most common techniques is partial ear canal ablation and bulla osteotomy (PECA-BO).
These surgeries are extensive and often the wounds are sutured open – a technique called ‘marsupialisation’ – to allow post-surgical flushing. This technique gives us the best chance at preventing the recurrence of infection. The choice of antibiotic is dependent on the results of culture, and sensitivity tests performed on surgical tissue samples (which are more accurate than culturing pus in rabbits). Flushing of the surgical sites is performed daily for several weeks following the surgery, which requires a lot of dedication from owners.
The intermittent use of ear cleaners designed to remove wax from ear canals may help reduce the risk – although there are no rabbit-specific ear cleaners on the market. No studies have been conducted into prevention strategies so far.
Dr Nadene Stapleton is part of the Royal Veterinary College’s Exotics and Small Mammals Service. She was named UK Rabbit Vet of the Year at last November’s Burgess Excel Vet Awards. The hospital in which she is based, the RVC’s Beaumont Sainsbury Animal Hospitalwas named Best Rabbit Practice of the Year.