BACTERIOLOGIC AND VACCINATION STUDIES IN A FIELD EPIZOOTIC OF INFECTIOUS BOVINE KERATOCONJUNCTIVITIS IN CALVES

  • 1 January 1976
    • journal article
    • research article
    • Vol. 37  (7) , 803-805
Abstract
Infectious bovine keratoconjunctivitis (IBK) was enzootic in the beef cattle herds at Dixon Springs Agricultural Center, University of Illinois [USA]. The development of nonhemolytic [N] and hemolytic [H] Moraxella bovis in the eyes of 48 calves in a closed cow-calf herd was monitored from late May-Oct., 1972. The incidence of clinical IBK was recorded each week. In late May, M. bovis N was isolated from 26% of calf eyes. The peak incidence of IBK was observed in early Sept. with 26% of the eyes affected. At that time, M. bovis N was isolated from 10% of the eyes, and M. bovis H from 58%. By late Oct., M bovis N was isolated from 25% of the eyes, and M. bovis H from only 4%. To increase the resistance of ocular tissue, 19 calves were vaccinated in each 3rd eyelid with 0.5 ml of an autogenous M. bovis bacterin in late May. Vaccination did not provide practical protection against the establishment of M. bovis H in the eyes, nor the development of clinical IBK. At the peak incidence of IBK, M. bovis H was isolated from the eyes of 48% of vaccinated calves and 73% of nonvaccinated calves; clinical IBK was present in 21% of the eyes of vaccinated calves and 29% of nonvaccinated calves. In evaluating the in vitro proteolytic potential of M. bovis isolates, 83 H and 5 N isolates peptonized litmus milk; 176 N isolates did not peptonize litmus milk. M bovis H isolates were more pathogenic for mice than were N isolates. Of 60 mice, 53 (88%) died 1-3 h after i.p. inoculation of H isolates; 8 of 32 (25%) mice died 5-15 h after inoculation of N isolates. M bovis H isolates produced testicular swelling and scrotal necrosis after inoculation into the scrotal sac of rabbits; N isolates produced only mild transient testicular swelling.

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