BASELINE ANTIBODY TITRE TO SALMONELLA TYPHI AND SALMONELLA PARATYPHI A AMONG APPARENTLY HEALTHY INDIVIDUALS IN ZARIA, KADUNA STATE, NIGERIA

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Department of Medicine

ABSTRACT
Typhoid fever is endemic in the tropics and sub-tropical regions of the world. It is a major public health problem in most developing countries including Nigeria. Efforts are ongoing to develop new test techniques and improve existing ones in order to mitigate the morbidities and mortalities of typhoid and paratyphoid infections. As such 180 serum samples from apparently healthy blood donors of the Department of Hematology, Ahmadu Bello University Teaching Hospital Zaria were evaluated for the levels of Salmonella typhi and Salmonella paratyphi A somatic O and flagella H antibodies using the quick tile technique and the Widal microtitire plate method to determine the baseline antibody titres. The standard Salmonella O and H (Oxoid/Remmel diagnostic) antigens were used. The presence of specific IgM/IgG antibodies was also tested among the subjects using the Typhidot IgM/IgG test cassettes. The occurrence of specific IgM in the study population was found in 3.9% of the samples studied while IgG occurred in only 1.1% of the population. The distributions of the antibody titres of S. typhi and S. paratyphi A among the subjects were determined. Since titres of ≤ 1:20, 1:20, 1:40, were found in a significant proportion (>80%) of the population tested for S. typhi O and H, the cut off titre for Salmonella typhi was found to be 1:80 for both O and H antibodies. Titres above 1:80 are therefore significant for the diagnosis of typhoid in our locality. For Salmonella paratyphi A, the cut off titre was found to be 1:40 for both anti O and anti H antibodies. Titres ≥ 1:80 are therefore significant titres for S. paratyphi A infections when using the Widal technique. A comparison of results from the tile method with the microtitre plate method showed a significant difference (p value 0.0001), indicating negative correlation between the quick tile method and the Widal microtitre plate method. The study has established the baseline titers, the cut off titre and the significant titres of vii Widal test for S. typhi and S. paratyphi A in Zaria. This study clearly demonstrates that there are deficiencies with the use of the quick tile technique in Widal testing and that the microtitre plate (MTP) method would be more appropriate and beneficial for Widal testing in this setting.