Infectious bovine keratoconjunctivitis in cattle vaccinated and medicated against Moraxella bovis before parturition.

A vaccination and prophylactic treatment study for infectious bovine keratoconjunctivitis (IBK) was conducted on selection line purebred Hereford and recombination mixed-breed cattle. In February, prepartum cows were allotted to 4 groups: group 1--mixed-breed cows vaccinated with a formalin-killed trivalent Moraxella bovis bacterin; group 2--Hereford cows vaccinated and treated with tylosin; group 3--Hereford cows treated with tylosin; and group 4--mixed-breed cows neither vaccinated nor treated (controls). Groups 2 and 3 were pastured together greater than 3 km for other cattle; cattle added to groups 2 and 3 were treated before being added. Groups 1 and 4 cattle were pastured together; cattle added to groups 1 and 4 were not treated. Cows, and subsequently their calves, were observed cursorily for clinical signs of IBK during the spring and early summer. The eyes of calves were examined in September and October 1979, and their eye secretions were examined for M bovis. The first clinical signs of IBK were seen in the herds in late July, and the largest percentages of acute disease were seen in mid-August. There were no significant differences (P = 0.18) in the percentages of calves that developed IBK, regardless of whether (or not) their dams were vaccinated. A larger percentage of the calves from tylosin-treated cows developed IBK than did calves from nontreated cows. The smallest percentage of disease was seen in calves of cows that were vaccinated only, but the differences were not significant (P greater than 0.10). The percentages of isolations of M bovis were similar (P = 0.23) among the 4 groups of calves. When compared on the basis of breed, the percentage of Hereford calves (62%) that developed IBK was greater than that of the mixed-breed calves (47%). When compared on the basis of color pattern, the percentages with IBK were significantly different (P less than 0.001). The percentages of IBK in calves were: red white-face (70%), black white-face (52%), black black-face with some white on body (40%), black (34%), and others (all color patterns not conforming to the 4 other groups; 21%). When compared on the basis of sire, the percentages of IBK in Hereford calves were significantly different (P less than 0.05). The percentages of affected calves ranged from 80% to 31%; the percentages of affected eyes ranged from 67% to 22%. When compared on the basis of sire, the percentages of IBK in mixed-breed calves were significantly different from each other (P less than 0.001). The percentages of affected calves ranged from 63% to 27% and the percentages of affected eyes ranged from 49% to 16%.