Base Line Widal Titres among Apparently Healthy Individuals in Srikakulam District, Andhra Pradesh

Abstract

Background: Enteric fever is an endemic problem in Srikakulam and Widal agglutination test is widely used for its diagnosis Aim and objective: The interpretation of the Widal test depends upon the baseline titre among healthy individuals in a particular geographical area. This study was undertaken to determine the baseline titre in apparently healthy individuals in Srikakulam District, Andhra Pradesh. Materials and methods: The average baseline antibody titres against O and H antigens of Salmonella enterica serotype typhi and H antigens of serotypes paratyphi A and B among apparently healthy blood donors (n=250) were determined by using Standard Widal confirmatory Quantitative tube test. Results: Among the 250 serum samples which were tested, 182 (72.8%) serum samples were positive for agglutinins against Salmonella serotypes (≥1:20). Among 182 samples with an anti-O titre ≥1:20, 60 (24%) samples had titres of 1:80. Among the 50 samples demonstrating anti- H titres of >1:20 to Salmonella serotype, 25 (10%) had a titre of 1:80. For Salmonella paratyphi A and B, anti -H titres of 1:20 were found in 8 (3.2%) and 8 (3.2%) respectively, for all samples tested. Conclusion: When a single Widal agglutination titre is used for diagnosis of enteric fever,it will be more appropriate to change the currently used cutoff levels against Salmonella enterica serotype typhi to >1:80 for anti- O and H of S. typhi and >1:20 for S. paratyphi A and B for Srikakulam district.