Leptospirosis

Leptospirosis

Leptospirosis is infection with the Spirochaete Leptospira. It is an acute zoonotic infection of worldwide significance. Leptospirosis is seen in both humans and animals.  The primary reservoir is rodents such as rats, mice, wild rodents and once infected, they shed the organisms for life. Livestock farming is the major occupational risk factor for human leptospirosis since cattle, dogs, swine etc., can also be reservoirs.

                                   

Infected animals excrete Leptospira both in active infection and asymptomatic stage. The Leptospira survive and remain viable for several weeks in stagnant water. It is common in temperate or tropical climates - rare in North America. Transmission to humans occurs through penetration of the organism into the blood stream via cuts, skin abrasions or mucus membranes

                                                    

Leptospirosis is also known as hemorrhagic jaundice, infectious jaundice, mud fever, spirochetal jaundice, swamp fever, swineherd's disease, caver's flu, sewerman's flu, Canicola fever (canine leptospirosis-dogs) etc

First human leptospiral disease was described by Adolf Weil in 1886, as an "acute infectious disease with enlargement of spleen, jaundice and nephritis. Leptospira was first observed by Stimson in 1907 from a post mortem renal tissue slice. Stimson named it Leptospira interrogans owing to its shape resembling interrogation (question) mark.

                          

Human infection also known as Weil's disease, is caused mainly by Leptospira icterohaemorrhagiae, which was isolated in 1915 by Inada. Consequently many leptospires have been isolated.

Spirochetes are divided into two families, Spirochaetaceae and Leptospiraceae. Spirochaetaceae –include Treponemes, Serpulina and Borrelia and Leptospiraceae include Leptospira.

Leptospira is further classified into several species and subspecies, called serogroups and serovars, based on the surface (lipopolysaccharide -LPS) antigens. Genus Leptospira is divided into two species -L. interrogans includes pathogenic strains and L. biflexa includes saprophyte strains -from the environment. These two species are divided into serovars  as defined by agglutination techniques. There are approximately 60 serovars for L. biflexa, more than 200 for L. interrogans.

L. interrogans has more than 22 serogroups common examples being L. icterohaemorrhagiae, L. Canicola, L. australis, L. hebdomadis, L. andamana, L. pyrogenes etc