Objective—To determine the immunogenicity of a
Moraxella bovis cytolysin-enriched vaccine for prevention
of infectious bovine keratoconjunctivitis (IBK).
Animals—104 mixed-breed beef calves ranging
between 4 and 8 months of age.
Procedure—Vaccines were prepared by the diafiltration
of broth culture supernatant from hemolytic
M bovisor or sterile media. The diafiltered retentate was
combined with Quil A adjuvant. Calves were randomly
assigned to receive either the cytolysin vaccine
(n = 35) or, as controls, adjuvant (35) or saline (0.9%
NaCl) solution (34). Eyes of all calves were examined
weekly for signs of IBK for 15 weeks. Calves that developed
severe IBK were treated SC with florfenicol.
Results—Cytolysin vaccine contained 4 proteins with
molecular masses ranging between 65 and 90 kd.
Cytolysin-vaccinated calves had fewer instances of
IBK than control calves. The time of onset of corneal
lesions in cytolysin-vaccinated calves that developed
IBK was delayed, compared with that of calves in
either control group. The cytolysin-Quil A vaccine contained
endotoxin, but calves did not have clinical signs
of illness after vaccination.
Conclusions and Clinical Relevance—Calves that
were vaccinated with a cytolysin-enriched vaccine had
some resistance to IBK. Vaccines containing concentrated
diafiltered M bovis cytolysin could protect beef
calves against IBK. (Am J Vet Res 2005;66:136–142)