Effectiveness of Vaccination in Controlling Ovine Footrot

Abstract

Efficacy of reducing footrot by use of a commercial vaccine was evaluated over 2 yr with 223 ewes from five crossbred genotypes. Ewes were assigned randomly within genotype, age and initial footrot status to a 2 × 3 factorial array of vaccination in the 1st yr and fall vaccination, winter vaccination or control in the 2nd yr. The flock contained a single Bacteroides nodosus serotype (XV) known to be highly cross-reactive with one of the vaccine serotypes (British serotype H). Vaccination reduced footrot incidence by 61% (P < .01) in the 1st yr and by 45% (P < .01) in the 2nd yr. Vaccination of previously uninfected ewes did not significantly reduce the rate of new infection, but vaccination of infected ewes reduced re-infection by 92% (P < .01). Vaccination in the 1st yr failed to produce any carryover or additive protection in the 2nd yr. Genotypes differed in both footrot incidence (P < .05) and footrot reduction following vaccination (P < .05), but the effect was inconsistent between years. Vaccination increased serum antibody titers in both years (P < .01). Among vaccinates in the 1st yr, infected ewes had lower titer levels than uninfected ewes (P < .01), but no correlation between titer level and incidence was observed in the 2nd yr. Copyright © 1989. American Society of Animal Science . Copyright 1989 by American Society of Animal Science