Leptospirosis sign. Sign warning of the dangers of contracting leptospirosis or Weil's disease from a contaminated watercourse. Leptospirosis is caused by Leptospira bacteria which are excreted in the urine of rats and other rodents. The presence of rodent urine in water can lead to infections in humans, dogs, and cattle. In humans the spiral- shaped bacteria cause fever, chills, aches, eye inflammation and a skin rash. The disease can also cause damage to the liver, kidneys, and nervous system. The illness can be treated by the use of antibiotics. Photographed in Hawaii, USA.