We found that the two mouse strains with a fully functional tlr4 gene (C3H-HeN and C57BL/6) also developed clinical and molecular signs of sublethal leptospirosis nearly on par with C3H-HeJ, as quantified by weight loss, survival curves, presence of Leptospira 16S rRNA in blood and urine, and burden of viable spirochetes in kidney. This evidence concerns the gene TLR4 and leptospirosis.