Prevalence of mycoplasmas and immune responses to Mycoplasma bovis in feedlot calves.

: Microbiological cultural, cytologic, and immunologic observations were made on 30 calves. The eyes, nares, and bronchioalveolar region were subjected to microbiological cultural examination for mycoplasmas. Four of the examinations of 30 eyes, 15 of those of 30 nasal tissues, and 25 of those of the 30 bronchioalveolar regions from the 30 calves were positive for mycoplasmas. Mycoplasma bovis and M bovirhinis were the most prevalent species. Cytologic examinations of peripheral blood and bronchioalveolar washes did not show pathologic changes. Results of indirect hemagglutination, enzyme-linked immunosorbent assay, lymphocyte-stimulation tests on peripheral blood cells, and skin testing demonstrated only a low prevalence of immune recognition of M bovis. Infection and immune response were studied in 3 calves for 10 weeks before, and for 4 weeks after, intratracheal administration of live M bovis.