The main infectious sources of leptospirosis are rats and pigs, among which the black-line gypsy rats are the main infectious source causing paddy-type leptospirosis, and the leptospires in their urine are discharged into the paddy fields, and farmers are easily infected when harvesting rice. And pigs because of close contact with people, their urine also contains a large number of leptospirosis, and pigs have a long period of excretion, so they can contaminate water, pig pens are wet and watery, there are also a large number of leptospirosis in the soil and stagnant water, other common animals that cause infection are dogs and cattle. While leptospirosis patients can also be excreted in the urine, but because human urine is acidic, and not suitable for the growth of leptospirosis. In addition, recessive infected individuals may also excrete bacteria, but their excretion rate is not high, so it is unlikely that humans are the source of infection.