Antibody levels to Salmonella typhi and paratyphi in Nigerians.

Objective: To determine the antibody titre levels to typhoid/paratyphoid fever organisms among apparently healthy volunteers.
Design: Cross sectional study.
Setting: General community and University Teaching Hospital.
Participants: Volunteer sample of 323 apparently healthy individuals with body temperatures < or = 37.8 degrees C.
Main Outcome Measures: Questionnaire administration to classify volunteers into three socio-economic status (SES).
Results: There were 35.29% of the apparently healthy population in Jos community with antibodies to typhoid/paratyphoid fever organisms. The presence of these antibodies were neither sex nor SES related. Normal antibody titres were up to 1:40 and 1:80 for O and H Salmonella antigens respectively. Contrary to the general belief, typhoid/paratyphoid fevers have not affected virtually everybody in Nigeria. The difference between those without previous history and those with previous history was significant (p < 0.05) with those in the former category having a higher percentage.
Conclusion: For a single sero-diagnosis to have any diagnostic value in Jos community and its environs, only a four-fold rise to what has been found to be normal should be significant. This means that only titres of 1:160 and 1:320 and above for O and H antigens should be considered significant.