Leptospirosis is a zoonosis (transmitted from animals to humans), caused by bacteria of the genus Leptospira, which have a particular spiral shape. The main natural reservoirs for the bacterium are small rodents (rats, mice), livestock (cattle, goats, horses, pigs) and pets (dogs, cats). All these animals excrete leptospires in their urine. The bacteria can survive for a few weeks in a hot and humid environment (stagnant water, muddy ground). 

Humans or animals become contaminated via the skin or mucous membranes (mouth, nose, eyes) through contact with water or contaminated soil, or through direct contact with an infected animal.

The people most at risk of infection are certain professional groups (breeders, veterinarians, garbage collectors, farmers, etc.), as well as people engaging in water sports in fresh water (fishing, kayaking, swimming, etc.).

In humans, leptospirosis can present with a wide range of clinical manifestations, ranging from mild flu-like illness to multiple organs potentially being affected. In the severe form (Weil’s syndrome), high fever, jaundice, impaired consciousness, hemolytic anemia and hemorrhagic manifestations are usually observed. 

In animals, an infection is generally asymptomatic in rodents and insectivores. In farm and domestic animals, brief bacteremia is followed by colonization of the kidneys and liver, where leptospires can lead to acute or chronic infections, manifesting as kidney and liver failure, loss of appetite, pulmonary hemorrhagic syndrome, infertility, jaundice, abortion as well as ocular complications such as uveitis.