Leptospirosis is a zoonotic disease re-emerging with high worldwide distribution, being endemic in tropical and subtropical regions.
In temperate zones, the disease is usually associated with occupational or leisure exposure, which facilitates contact with leptospires, the causative agents.
Leptospires are spiral-shape and motile bacteria, belonging to the complex Leptospira interrogans sensu lato including more than 260 pathogenic serovars for humans and animals.
Leptospira transmission is done by direct or indirect contact with contaminated water or soil by urine of animals, especially rodents (the natural reservoirs) and /or infected hosts.
Generally, rodents are mainly responsible for the spread of leptospires in the environment, although some animals (cattle and pigs) also be considered “chronic renal carriers” throughout life.
The human contact is accidental and results either from a professional exposure (slaughterhouse workers, farmers, construction and sanitation workers and others) or by contact with freshwater collections in leisure activities (fishing, boating and swimming in dams, ponds or even in golf practice).
Clinically, the disease can be confused with a cold, may, however, be fatal in severe cases (about 10% in temperate zones) due to septic shock, acute renal failure or haemorrhagic pneumonia. If diagnosed in time, it has a more favourable prognosis because leptospires are very sensitive to antibiotics in the early phase of the disease.
In Portugal, leptospirosis has had a growing importance in recent decades, with the occurrence of fatal cases, particularly in the Azores Archipelago, where the disease is endemic, leading to the implementation, in recent years, of integrated campaigns on prevention, control and surveillance especially in the two most populous islands (São Miguel and Terceira).
As regards the diagnosis, it is up to the laboratory confirm the clinical suspicion, especially by reference test (Microscopic Agglutination Test) recommended by WHO and by actual molecular approaches.