Currently only phenotypic epidemiological markers, serogrouping and virulence testing of
Dichelobacter nodosus, are available for investigating footrot outbreaks in small ruminants.
These methods have limitations in tracing the source of infection. In this study, a genotypic
marker, PCR–RFLP of outer membrane protein gene, was used to characterize D. nodosus. The
technique was evaluated in a controlled experiment involving two strains of bacteria.
PCR–RFLP was found to be highly specific in differentiating isolates obtained from recipient animals
infected with different strains. Subsequently, this technique was used to characterize isolates
obtained from field cases of footrot in Nepal. A total of 11 patterns was recognized among 66
Nepalese D. nodosus isolates representing four different serogroups. PCR–RFLP also
discriminated isolates with similar phenotypic characteristics. However, all isolates which,
phenotypically, were virulent were represented by only two patterns irrespective of their
serogroups. It is suggested that PCR–RFLP described here could be a useful epidemiological
marker in the study of footrot.