Studies on the incidence of leptospirosis and possible transmission of Leptospira during leptospiraemia.

During the year 1991 and in the first half year of 1992 a total of 179 cases and 288 cases respectively were tested for the presence of Leptospira by dark ground microscopy and 86 cases (48%) and 157 cases (54.5%) were found to be positive for Leptospira in their blood samples only. The disease was endemic and more prevalent in the age group of 5 to 14 years and 15 to 54 years and affected both sexes. Clinical categorisation of 169 cases in 1991 and 266 cases in the first half of the year 1992 along with the dark ground microscopy results showed that there was no strict correlation between the concentration of Leptospira in the blood and the severity of infection. Epidemiological data regarding the occupation and the contacts indicated that students and medical staff accounted for more than fifty percent of leptospiral infection and there was the possibility of transmission of Leptospira during leptospiraemia. Dark ground microscopy studies on blood samples from 20 cases who came for repeat testing showed the presence of Leptospira in blood up to 43 days and suggested that the convalescent carrier may have a role in the transmission of Leptospira during Leptospiraemia.