Isolation and Serotyping of Endemic Leptospires of West and Central Regions of Flat Areas of Guilan Province

Leptospirosis is a zoonosis which is more widespread in the tropical and semi tropical regions, and is endemic in the flat area of Guilan province, north of Iran. Surface waters are sources of saprophytic and carier animals are reservoirs of pathogenic agent. In each endemic region only a limited number of pathogenic serovars are common, and characterization of them is a very important step in detecting the main reservoirs of the disease. This study is performed to isolate endemic leptospires from rice farms, irrigation canals, and rivers of west and central parts of the area, which accounted for a significant annual incidence of the disease. In this cross-sectional study, 500 specimens were taken from 13 cities of the area, between May to September of 2007. One ml of each water sample was inoculated in EMJH liquid medium with 200µg/ml 5-flurouracil after filtration by 22 µm syringe filter. All speciments were incubated in 30ºc for 3 months and were checked by darkfield microscope every 2 weeks. All positive samples were characterized by using 30 types antisera. One hundred thirteen of 500 specimens were positive. Saprophytic serogroups were Andamana and Semaranga, belonging to biflexa species. Pathogenic serogroups were icterohaemorrhagiae, pomona, canicola and pyrogenes (interrogans Specie), hardjobovis and sejroea (Borgpeterseni specie), grippotyphosa (Kircshneri). Pathogenic species were common in the rice paddies and saprophytic species were common in the rice farms, rivers and irrigation canals, respectively. Conclussion: It seems that higher frequency of pathogenic serogroups in rice farms is due to high traffic of animals and rodents, and the long time stay of water in the farms. Isolation of saprophytic serogroups in all types of surface waters was expected. Increasing farmer's knowledge about the ways of the disease transfer, and avoiding of unprotected contact with surface waters might help with decreaseing the incidence of the disease in the area.