serological study for measuring rate of leptospirosis in patients who encountered “shaltook fever”

in guilan province, near the end of spring and summer each year at the time of rice gathering, some of the farmers run high fevers. this disease is named as “shaltook fever” (paddy or husked rice fever) in the region. review of literature showed outbreak of leptospirosis between rice farmers in italy and spain. we decided to measure antibody levels (igm and igg) against leptospirosis in patients with shaltook fever. samples were chosen from any patient who was diagnosed as shaltook fever by health care clinics between end of spring and summer of 2002 in guilan province. patients should have fever above 38° c, with myalgia and history of recent work at rice fields. all other diagnosis for these patients should have been ruled out by clinical or laboratory investigations. antibodies levels were measured by elisa method. igm was measured in 87 out of 100 serum samples and igg was measured in 84 out of 87 of above serum samples. in 26 samples igm anti leptospira were positive (igm > 20 u/ml), and 5 specimens were borderline (igm = 15-20 u/ml). in measuring igg, 10 samples were positive (igg > 9 u/ml), and 13 samples were borderline (igg = 5-9 u/ml). the above findings were suggestive of acute leptospirosis infection in 30% of shaltook fever patients. it is of interest that in only 17 out of 26 positive samples for igm positive igg titers were observed. it could be concluded that these patients had, for the first time recently, encountered the disease.