Comparison of footbathing and vaccination to control ovine footrot in an experimentally infected flock.

Abstract

OBJECTIVE: Compare footbathing and vaccination for control of footrot during a transmission period in a sheep flock deliberately infected with multiple strains of Dichelobacter nodosus. METHODS: The strains included a known virulent strain, a benign strain and several intermediate strains. The resulting footrot was clinically intermediate. A total of 1450 Polwarth sheep aged 1-3&#x2009;years were allocated to one of five treatment groups: untreated, weekly walkthrough zinc sulfate footbathing, 1-hour stand-in Footrite&#xae; footbathing every 3&#x2009;weeks, vaccination with a commercial multivalent whole-cell vaccine and vaccination with a novel recombinant DNA fimbrial vaccine. There were four replicates, in four paddocks. RESULTS: Of the untreated animals, 76% had footrot. Footbathing, either weekly or every 3&#x2009;weeks, restricted the prevalence to 6/283 (2%; 97% effective) and 18/275 (6.5%; 91% effective), respectively. This was significantly lower than the prevalence in either the untreated or vaccinated group (P&#x2009;<&#x2009;0.001). Weekly footbathing resulted in significantly fewer affected sheep than footbathing for 1&#x2009;h every 3&#x2009;weeks (P&#x2009;<&#x2009;0.05). Vaccination with either whole-cell or recombinant vaccines significantly (P&#x2009;<&#x2009;0.001) reduced the prevalence ((142/280 (51%; 33% effective), 114/278 (41%; 46% effective) respectively), with the recombinant vaccine superior (P&#x2009;<&#x2009;0.05) to whole-cell vaccination. Significantly (P&#x2009;<&#x2009;0.05) fewer 1-year-old sheep had footrot than older sheep. A single Footrite treatment reduced the prevalence to 12% (53/445) compared with a prevalence of 57% (27/47) for untreated sheep (79% effective). CONCLUSION: In this study footbathing was more effective than vaccination at controlling and treating multistrain footrot.