The bacteria that cause leptospirosis are spread through infected animals' urine, which can enter water or soil and survive for weeks to months. The bacterium is carried by a wide range of wild and domestic animals. Renal failure in animals can be caused by anything that reduces blood flow through the kidney. Dehydration from any source, heatstroke, or other disorders causing massive tissue damage, such as bee stings or snakebites, can all lead to kidney failure. When animals consume the bacteria, they circulate in the bloodstream and enter the kidneys via the glomerulular or peritubular capillaries. The bacteria then enter the renal tubule lumens and colonise the brush border and proximal convoluted tubule. This results in the continuous shedding of bacteria in the urine without causing significant harm to the animal. This is referred to as a commensal relationship between the animal and the bacteria, and the animal is referred to as a reservoir host. The presence of these bacteria activates endothelial cells in the human body's capillaries via the innate immune system. Endothelial cells generate cytokines and antimicrobial peptides in response to bacteria. These substances control the coagulation cascade and the movement of white blood cells.