(A) Twenty-four-day-old C57BL/6J mice were inoculated with PBS (n = 3), or 103 PFU of RR64 (n = 4), RRV strain DC5692 (n = 5), or the molecular clone of DC5692, RR87 (n = 5) by injection in the left rear footpad. Mice were scored for the development of disease signs including loss of gripping ability, hind-limb weakness, and altered gait. Each data point represents the arithmetic mean ± standard deviation (SD). Data was evaluated for statistically significant differences by ANOVA (P < 0.0001) followed by Bonferroni’s Multiple Comparison Test. (B) At 10 dpi, mice were sacrificed and perfused with 4% paraformaldehyde. 5 micron-thick paraffin-embedded sections generated from quadriceps muscles were stained with H&E. Images are representative of three mice per group.