Causative Factors of Leptospirosis


Leptospirosis is caused by Leptospira interrogans, a corkscrew–shaped bacterium (spirochetae). Outbreaks of leptospirosis are usually caused by exposure to water contaminated with the urine of infected animals. Many different kinds of animals carry the bacterium, they may become sick but sometimes have no symptoms.

Leptospira organisms have been found in cattle, pigs, horses, dogs, rodents, and wild animals. Humans become infected through contact with water, food, or soil containing urine from these infected animals. This may happen by swallowing contaminated food or water or through skin contact, especially with mucosal surfaces, such as the eyes or nose, or with broken skin.

Risk Factors

Leptospirosis is primarily an occupational disease that affects farmers, veterinarians, fish workers, dairy farmers, or military personnel or others whose occupation involves contact with animals, especially rats. Leptospirosis is spread mainly by the urine of infected animals and is generally not transmitted from person to person. Leptospirosis occurs all over the world but is most common in temperate or tropical climates with heavy rainfall. It is a recreational hazard for campers or those who participate in outdoor sports in contaminated areas, and has been associated with swimming, and whitewater rafting in contaminated lakes and rivers. The incidence is also increasing among urban children. Infected rodents and other wild and domestic animals pass the bacteria in their urine. The bacteria can live for a long time in fresh water, damp soil, vegetation, and mud. Flooding after heavy rainfall helps spread the bacteria in the environment. Worldwide, rats are the most common source of human infection