Bovine Infectious Keratoconjunctivitis: Interactions of Moraxella bovis and Infectious Bovine Rhinotracheitis Virus

Abstract

SUMMARY Eyes of cattle were exposed to Moraxella bovis organisms and infectious bovine rhinotracheitis ( ibr ) virus by conjunctival sac instillation under different schedules. In one experiment, the eyes of 10 cattle were exposed to M. bovis and 41 days later to ibr virus. Five of 10 cattle developed unilateral bovine infectious keratoconjunctivitis ( ibk ) before they were exposed to ibr virus. Cattle did not develop keratitis when ibr virus was introduced, but all 10 cattle developed bilateral conjunctivitis. The eyes of 10 other cattle were exposed to M. bovis and ibr virus concomitantly. Six cattle developed severe unilateral keratoconjunctivitis, and 4 developed severe bilateral keratoconjunctivitis. The other eye of each of the 6 cattle with unilateral ibk developed severe conjunctivitis. In another experiment, the eyes of 10 cattle were exposed to ibr virus and 24 days later were exposed to M. bovis . All cattle developed severe bilateral conjunctivitis attributable to ibr virus. Keratitis was not produced before cattle were exposed to M. bovis ; after exposure to M. bovis , 4 developed unilateral ibk and 3 bilateral ibk . When 6 control cattle were exposed to M. bovis only, 2 developed unilateral ibk , and 3, bilateral ibk . Seemingly, ibr virus is not the primary etiologic agent of ibk , but the eye disease caused by ibr virus enhances the pathogenic effects of M. bovis by creating a more suitable environment for the organism.