Using a mouse strain with impaired TLR4 sensing (C3H-HeJ) and a relatively high dose of inoculum (106 spirochetes), we developed a mouse model of persistent Leptospirosis in which we can measure empirical clinical signs of infection such as weight-loss and a number of other metrics that allow us to qualify and quantify differences in pathology in 10 week old mice [9]. This evidence concerns the gene TLR4 and infection.