Clinical and microbiological study of an otitis media outbreak in calves in a dairy herd.

On a dairy farm, otitis media was diagnosed in 64 suckler calves (21.8%) during a study period of 2 years, and in 10 calves (3.4%) in the third year. The inflammation was unilateral in 63 and bilateral in 11 calves. The affected calves were dull, lacked appetite, were pyrexic and displayed drooping ear or ears and tilted heads with purulent discharge exuding from the external ear canal. Of the affected animals, 56 (87.5%) were aged between 3 and 8 weeks. Morbidity was higher during the calving season and during the autumn and winter months (October-December). Pasteurella haemolytica was isolated from 21 (32.8%), P. multocida from 20 (31.2%), Actinomyces pyogenes from 11 (17.2%) and Streptococcus pneumoniae from three (4.7%) of the clinically affected calves only during the first two study years. The exudate of the acute ear infections contained, in addition to Pasteurella spp., various bacteria and yeasts. Most of these bacteria were isolated from healthy ears as well, and are likely to be part of the normal ear flora. On the other hand most of the yeasts were isolated from otitic calves. After a short course of an appropriate treatment infections healed in all cases. Possible preventive measures are discussed.