Cause and pathogenesis of middle ear infection in young feedlot cattle.

Two populations of feedlot cattle--weaned calves and yearlings--suffered otitis media. In calves the disease was acute and epizootic and had a prevalence of about 400 cases per 2000 cattle, whereas in yearlings, it was chronic and sporadic and had a prevalence of 1 case per 2000 cattle. Clinical signs were facial paralysis, otorrhea, and head tilt. The middle ears from 64 dead calves and 22 dead yearlings were examined. Calf ears had acute infection, with exudate in air cells and rupture of tympanic membranes. Yearling ears had chronic infection, with exudate in air cells, rupture or destruction of tympanic membranes, and necrosis of air cell partitions. Mixtures of Pasteurella multocida and Corynebacterium pseudotuberculosis were isolated from diseased ears, but Pasteurella multocida predominated in acute infections and Corynebacterium pseudotuberculosis predominated in chronic infections.

Middle ear infection in feedlot lambs.

Of 133 feedlot lambs that died and were necropsied, 67 had normal lungs and 66 had pneumonic lungs. The middle ears of all lambs were opened by a specified technique. Of the 67, 8 (12%) had otitis media, and of the 66, 26 (39%) had otitis media. The difference in prevalence in the 2 groups was highly significant (P less than 0.005). In acute stages, the mucosae of tympanic cavities and tympanic membranes were inflamed and the cavities contained fluid, whereas in later stages lumens were partially filled with exudate. In chronic stages, however, exudate remained in lumens and mucosae were thick and rough. None of the tympanic membranes was ruptured, and none of the external acoustic meatuses contained exudate. The infected ears of 24 lambs were cultured and Pasteurella haemolytica was isolated from 18, and P multocida from 3. The infections probably ascended from the pharynx through the auditive tubes into the tympanic cavities.

Ischemia: a cause of hepatic telangiectasis in cattle.

We histologically examined (i) 73 bovine livers condemned by packing house inspectors for telangiectasis, (ii) 15 bovine livers passed by the same inspectors as normal, and (iii) 8 livers from cattle given an injection into their mesenteric veins: 6 with a suspension of agar particles containing viable Haemophilus somnus and 2 with diluent only. The injected cattle were killed and necropsied 2 to 12 days after the inoculations. Of the 73 telangiectatic livers, 57 (78%) had thrombosed and occluded or contracted and empty portal veins (venopathies), whereas 1 of the 15 normal livers contained one microscopic focus of telangiectasis and nearby venopathy. Of the 6 livers injected with suspended particles, all had venopathies and telangiectasis and the 2 control livers had neither.