A prevalence study of typhoid fever and convalescent phase asymptomatic typhoid carriers among the schoolchildren in the northern part of Tamil Nadu

Abstract

This study reports, for the first time, the prevalence of typhoid fever and convalescent phase asymptomatic typhoid carriers among the schoolchildren in Vellore district of Tamil Nadu state in India. Blood and stool samples (n = 500) were collected from the schoolchildren, who were admitted to District Government hospitals for treatment of typhoid fever or other enteric disorders. Early morning stool and blood samples (n = 700) were collected from the schoolchildren, who had the previous history of typhoid fever. The blood and stool samples were subjected to immunological and bacteriological examination to confirm the cases of typhoid fever and typhoid carriers. Further, S. Typhi isolates from the typhoid patients and asymptomatic carriers were serogrouped by standard protocols at WHO Reference laboratory for Salmonella typing in India. A total of 360/500 (72%) children were positive for typhoid fever; while a total of 147/700 (21%) children were confirmed as convalescent phase asymptomatic typhoid carriers. All the S. Typhi isolates obtained from children positive from typhoid fever or typhoid carriers in this region were found to be serovars 9, 12, Vi: d and 4, 12: i: 1, 2. This study highlights the prevalence of typhoid fever among the schoolchildren and a possible role of convalescent phase asymptomatic typhoid carriers as a risk factor for the spread of infection in this locality.