Leptospirosis is a worldwide zoonotic infection with greater incidence in tropical regions. The epidemiology of leptospirosis has been modified by changes in animal husbandry, climate, and human behavior. Early initiation of antibiotic is very important in acute disease. Identified as one of the emerging infectious diseases, exemplified by the recent outbreaks in Nicaragua, Brazil, India, southeast Asia, the United States, and most recently in Sabah in Malaysia. Interest surged up from large clusters of cases which have occurred in Central and South America following flooding. This type of infection with zoonosis ranges fom subclinical infection to a severe syndrome of multiorgan infection with high mortality. This syndrome, icteric leptospirosis with renal failure, was first reported over 100 years ago by Adolf Weil. It has been suggested that Leptospira interrogans serovar icterohaemorrhagiae was introduced to Western Europe in the 18th century by the westward extension of the range of Rattus norvegicus from Eurasia.

The etiology of Leptospirosis was demonstrated in 1915 in Japan and Germany. Spirochetes were found and specific antibodies in the blood of Japanese miners with infectious jaundice. In Germany, soldiers affected with French disease, were found to be afflicted L. interrgans, with Leptospirosis. The spirochetes had hooked ends, and the role of the rat as a source of human infection was discovered in 1917, while the potential for leptospiral disease in dogs was recognized. In 1989, the genus Leptospira was divided into two species, L. interrogans, comprising all pathogenic strains, and the L. biflexa, containing the saprophytic strains isolated from the environment. Microscopic examination show leptospires as tightly coiled spirochetes, usually 0.1 um by 6 to 0.1 by 20 um, but occasional cultures may contain much longer cells. The helical amplitude is approximately 0.1 to 0.15 um, and the wavelength is approximately 0.5 um. The cells have ointed ends, either or both of which are usually bent into a distinctive hook. Two axial filaments with polar insertions are llocated in the periplasmic space. Leptospires exhibit two distinct forms of movement, translational and nontranslational. Letospires have a double membrane structure common to spirochetes.Leptospires are obligate aerobes wkith an optimum growth temperature of 28 to 30 degrees centigrade. They produce both catalase and oxidase. Leptospires are phylogenetically related to other spirochetes. Leptospirosis is presumed to be the most widespread zoonosis in the world and the source of infection in humans is usually either direct or indirect contact with the urine of an infected animal. The incidence is relatively higher in warm-climate countries than in temperate regions.This is due mainly to the longer survival of leptospires in the environment in warm, humid conditions. The disease is seasonal, with peak incidence occurriong in summer or fall in temperate regions, where temperature is the limiting factor in survival of leptospires, and during rainy seasons in warm-climate regions.The usual portal of entry is through abrasions or cuts in the skin or via the conjuntiva. Infection may take place via intact slin after prolonged immersion in water, but this usually occurs when abrasions are likely to occur and is thus difficult to substantiate. Water-borne transmission has been documented and contamination of water supplies has resulted in several outbreaks of leptospirosis. Inhalation of aerosols or water also may result in infection of the mucous membranes of the repiratory tract. Rarely, infection may follow animal bites. Direct transmission between humans has been demonstrated rarely. However, excretion of leptospires in human urine months after recovery has been recorded. Transmission by sexual intercourse during convalescence has been reported. Animals including humans can be divided into maintenance hosts and accidental hosts. A maintenance host is defined as a species in which infection is endemic and is usually transferred from animal to animalbhy direct contact. Other animals including humans may become infected by indirect contact with the maintenance host, which may cause severe or fatal disease. The clinical presentation of leptosirosis is biphasic, with acute or septicemic phase lsting ablut a week, followed by the immune phase, characterized by antibody production and excretion of leptospires in the urine. Most of the complications lof leptospirosis are associated with localization of leptospires within the tissues during the immune phase and thus occur during the second week of the illness.