Leptospirosis – an old and re-emerging bacterial zoonosis

Leptospirosis, a disease of the past?
Back 130 years ago, the German physician Adolf Weil described four cases of a “peculiar disease with splenic tumor, icterus, and nephritis”, starting his description with the statement that this disease was “undoubtedly included in the group of infectious diseases” [1]. At that time, severe icteric febrile diseases were numerous and not easily differentiated one from another. The so-called “yellow fever of temperate zones” (most probably frequently leptospirosis) was thought to be caused by exposure to specific, somehow toxic, environments (notably freshwater, soils, mud) and particular climatic conditions (mainly season and rainfall) [2].

Adolf Weil was right: three decades later, talented Japanese microbiologists reported the identification of the causative bacterium Spirochaeta interrogans [3], now known as Leptospira interrogans. This thin helical-shaped microorganism belongs to the phylum Spirochetes – a unique group of bacteria. Within less than 5 years, Japanese medical doctors and microbiologists established the whole picture of leptospirosis almost as it is known now. Inada and colleagues described the mode of infection of this “epidemic and endemic disease”, including through the skin [4], while Noguchi identified wild rats as a reservoir of the pathogenic bacteria [5]. Interestingly, empirical association with water and soils was also relevant and Noguchi prophetically questioned about the survival of pathogenic leptospires in natural environments, including in water and soils [6].

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