Infectious bovine keratoconjunctivitis: experimental induction of infection in calves with mycoplasmas and Moraxella bovis.

Eyes of 14 calves were exposed by conjunctival instillation to cultures of either Mycoplasma conjunctivae (6 calves) or Acholeplasma laidlawii (8 calves). Calves were observed for clinical signs of infectious bovine keratoconjunctivitis (IBK), and eyes were examined for the test organisms by bacteriologic cultural technique for 60 days. Acholeplasma laidlawii became established in the eyes of 5 of 8 calves; M conjunctivae became established in the eyes of 4 of 6 calves. On day 28, eyes of 9 of the 14 calves were exposed by conjunctival instillation to Moraxella bovis, and all developed IBK. Five calves exposed to Moraxenjunctivae or A laidlawii, but not to Mor bovis, did not develop IBK. Four calves not exposed to M conjunctivae or A laidlawii, but exposed to Mor bovis, developed IBK. Mycoplasmas do not have a major role in IBK, but might produce ancillary effects similar to those of infectious bovine rhinotracheitis virus, wind, ultraviolet radiation, dust, and other irritants.