Concurrent respiratory pathology and intracranial extension are common in companion rats (Rattus norvegicus) with...

Otitis media/interna is well described in laboratory rats, but there is limited information on treatment and prognosis in pet rats.

This was a retrospective, multi-institutional study of companion rats (Rattus norvegicus) presenting with otitis media/interna between 2011 and 2025. The inclusion criteria were rats diagnosed with otitis media/interna via imaging, necropsy or both. Information extracted from the medical records included signalment, clinical signs, diagnostic findings (including imaging, bloodwork, gross necropsy, histopathology and microbiology), treatment and survival time.

Twenty-three rats met the inclusion criteria. Twelve were diagnosed via necropsy alone, nine via imaging alone and two via both imaging and necropsy. Fifteen had clinical signs suspected to be due to otitis media/interna with or without otogenic intracranial disease. Seven had evidence of intracranial extension, such as meningoencephalitis or rhombencephalitis. Eighteen had concurrent respiratory disease. Bacterial culture (14/23) of lung, ear and/or brain samples revealed various bacteria, including Staphylococcus aureus (3/14). Mycoplasma was identified in six cases (three via PCR, two via culture and one via next-generation sequencing). Treatments included antibiotics (17/23), meloxicam (7/23), corticosteroids (3/23) and myringotomy (2/23). Survival ranged from 0 to 341 days.

This was a retrospective study, and case details and follow-up were limited in some cases.

Over three-quarters of rats with otitis media/interna had concurrent respiratory disease and almost one-third had intracranial extension. Advanced imaging should therefore be considered in rats presenting with respiratory or neurological signs.