A PATHOLOGICAL AND BACTERIOLOGICAL STUDY ON OTITIS-MEDIA IN SWINE

A pathologic and bacteriologic study on otitis media in swine was performed on 237 swine, ranging in age from 1 day to 1 year. These 237 swine from eight selected farms were slaughtered due to unfavorable prognosis associated with clinical signs of illness. One hundred sixty-three (68.8%) of the 237 swine were found to be affected with otitis, though only a few swine showed clinical signs characteristic of the disease. One hundred fifty-one (63.7%), 53 (22.4%), and 39 (16.5%) had lesions in the middle, external, and internal ear, respectively. Of the 151 cases with otitis media, bilateral and unilateral infection accounted for 114 (75.5%) and 37 (24.5%), respectively. Only 5/53 swine with otitis externa and 6/39 swine with otitis interna failed to show otitis media. All swine with infection in the tympanic cavity had inflammatory lesions in the auditory tube. Examination of the swine grouped by age revealed that, regardless of age, incidence of otitis media was 50-70%. In swine younger than 1 month old, otitis media tended to center on the auditory tube, where a mild infiltration of neutrophils into the mucous membrane was frequent. Thereafter, otitis media increased in degree and extent with age. Forty (26.5%) of the 151 swine affected with otitis media were accompanied by a substantial amount of inflammatory exudate in the tympanic cavity and bulla. Purulent exudate was found in 20/40 (50%) swine. Severe otitis media prevailed in swine between 1 and 4 months of age, showing inspissation of a suppurative exudate in the tympanic cavity and lysis of the underlying osseous wall of the tympanic bulla with subsequent fibrosis. Microorganisms, such as Pasteurella multocida, coryneform group E, and Actinomyces pyogenes, were the prominent isolates from the exudate in the tympanic cavity or in the tympanic bulla of the 19 swine examined. Most cases of otitis externa and interna (the latter infection frequently [22/23] extended to the brain) were associated with severe otitis media. Based on these results, otitis media prevails from the early stages of life and occurs first as an acute inflammation in the auditory tube, and then extends to the other components of the ear and the brain.