Otitis media is a bacterial, and occasionally parasitic or fungal, infection of the middle ear in small mammals. The middle ear consists of the tympanic bulla, a bony cavity housing the auditory ossicles (the tiny bones that transmit sound vibrations from the eardrum to the inner ear), and connects to the nasopharynx via the eustachian tube. When this space becomes infected, it fills with inflammatory debris and purulent material, causing pain, potentially affecting hearing, and risking extension to the inner ear where life-threatening vestibular dysfunction can result. Otitis media is a common and clinically significant condition in small mammal veterinary practice.
This condition affects virtually all small mammal species, with rabbits, rats, guinea pigs, chinchillas, and hamsters being most commonly diagnosed. In rabbits, otitis media is frequently caused by Pasteurella multocida, a bacterium that commonly inhabits the respiratory tract and spreads to the middle ear through the eustachian tube. Lop-eared rabbits are predisposed due to ear anatomy that interferes with normal ear canal drainage and ventilation. In rats, middle ear infection often develops secondary to chronic Mycoplasma respiratory disease. The prevalence varies by species and population but is substantial in clinical practice.
The impact of otitis media on affected animals includes significant pain and discomfort. The enclosed tympanic bulla does not drain effectively, and accumulation of purulent material increases pressure and inflammation. Hearing may be diminished if the ossicles are damaged or immobilized by inflammatory debris. Facial nerve involvement can occur, as this nerve passes through the middle ear, potentially causing facial paralysis. The greatest concern with otitis media is progression to otitis interna, infection of the inner ear, which causes vestibular dysfunction manifesting as head tilt, loss of balance, circling, and rolling. This progression significantly increases morbidity and mortality.
Otitis media is treatable, but treatment is typically prolonged and requires commitment from owners. Antibiotic therapy must continue for weeks to months to eradicate infection from the enclosed bulla. In some cases, surgical intervention is necessary to drain the bulla and remove infected material. The key to successful treatment is early detection and aggressive therapy before infection extends to the inner ear. Small mammal owners should be aware that subtle ear discomfort may indicate developing otitis media, and veterinary care from a practitioner experienced in exotic small mammal medicine should be sought promptly. The prognosis is generally favorable with appropriate treatment but worsens significantly if the inner ear becomes involved.
