Abstract
In the course of post-mortem examination of conventional random-bred and inbred (immunosuppressed) strain 2/N guinea pigs kept in separate quarters, otitis media was diagnosed in 62 of 462 animals (13·4%) and 18 of 66 animals (27·3%) respectively. Clinical signs of otitis media were seen in only two randombred animals but in nearly 50% of affected inbred animals. In random-bred guineapigs, purulent, often bilateral, otitis media was associated mainly with the isolation of Streptococcus zooepidemicus, Bordetella bronchiseptica, Pasteurella and Actinobacillus spp. and micrococci. In strain 2/N guineapigs serous or purulent often bilateral otitis media was associated mainly with the isolation of B. bronchiseptica and Pseudomonas aeruginosa serotypes 10 and 11. The simultaneous occurrence of similar pathogenic bacteria in both ears of bilaterally affected animals and in pneumonic lung tissue (in random-bred animals) suggested ascending and descending infection originating from the upper respiratory tract. It is concluded that otitis media, associated with the isolation of a variety of respiratory bacterial species, must be considered a major disease problem in guineapigs.