Otitis media of guinea pigs

The incidence of middle ear disease in guinea pigs is difficult to assess, since the number of animals affected in a colony depends, to a large extent, on the overall microbial status of a particular colony. Also, otitis media is usually a clinically inapparent infection. It occurs more commonly in colonies of guinea pigs carrying latent upper respiratory infections than in colonies without such infections. At necropsy, the suppurative contents of the tympanic bulla affected with otitis media can be used as an indicator of latent upper respiratory infection and as a source of inocula for cultural isolation of pathogens. Otitis media occurred in 177 of 1373 guinea pigs necropsied during a 6 yr period. Streptococcus pneumoniae (20%), Streptococcus zooepidemicus (15%), Bordetella bronchiseptica (12%), and Pseudomonas aeruginosa (11%) were the most common bacteria isolated from affected tympanic bullae. Radiology and otoscopy were tested as means of antemortem screening for affected guinea pigs. Radiology gave 96% accuracy in diagnosing otitis media and proved to be a more satisfactory technique than otoscopy.