Leptospiral strains belonging to L. interrogans serogroup Icterohaemorrhagiae have been confirmed to cause acute lethal leptospirosis in young C3H/HeJ mice, a TLR4-deficient strain [55], with typical pathological changes such as hemorrhage, infiltration of inflammatory cells and vasculitis in the lung as well as diffuse inflammation and tubular necrosis in the kidney [29]–[31]. The gene discussed is TLR4; the disease is vasculitis.