Alternatively, aborted fetuses, afterbirth or uterine discharges can contaminate the environment. Infected bulls can also transmit the infection through semen to females in the herd. Infected swine have been known to pass the organism in their urine for up to two years. These long term shedders are of particular importance because they transmit the disease to younger animals in the herd or, if sold, transmit it to the purchaser's herd. The organism can survive for up to six months in moist, warm conditions.
Stagnant water is an ideal source of infection.
For these reasons, leptospirosis is seen most frequently in areas of the world that have a temperate climate and a high rainfall. In cattle, the age group most susceptible to the acute form of leptospirosis is calves up to one month of age. Jaundice is commonly observed, and blood colored urine is passed. The calves often develop anemia, which results in an increase in respiratory and heart rates. The death rate is frequently high, and any calves that do survive may undergo a long convalescence.