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

vi

CHAPTER ONE

1.0       INTRODUCTION

Every year, thousands of cases of typhoid and paratyphoid infections are reported

worldwide (Hurley et al., 2014). Salmonella enterica serovar typhi (S. typhi) and

Salmonella paratyphi A,B,C are the causative agents of enteric fevers. Typhoid fever is

an acute, life threatening febrile illness caused by S. typhi which results in about

200,000 deaths worldwide each year largely in developing countries (Crump and

Mintz, 2010). Salmonella typhi infections exact a heavy toll on human populations

particularly among children. Despite the explosion of knowledge on the pathogenesis of

enteric diseases experienced during the past decade, the number of diarrheal episodes

and human deaths reported worldwide remain remarkably high (Fiorentino et al.,

2013).

Due to the importance of Salmonella in the clinical and public health setting, there has

been a significant effort to improve on the laboratory diagnosis of typhoid and

paratyphoid fever. The definitive diagnosis of typhoid fever requires the isolation of

Salmonella typhi from blood, feces, urine, or other body fluids (Kataria et al., 2013). In

developing countries facilities for isolation and culture are often not available

especially in primary and secondary health institutions. However, where facilities are

available, easy access to across the counter drugs by patients especially antibiotics

make isolation of the organism difficult. Diagnosis relies greatly upon the clinical

features and the detection of agglutinating antibodies to S. typhi by the Widal test.

Various investigators have given varying views on the diagnostic value of a single

pretreatment Widal test (Frimpong et al., 1999; Ibekwe et al., 2008). While some found

1

the test valuable, others found it of limited use. However, all the authors arrived at the

consensus that for a reliable interpretation of the Widal test, the circulating Salmonella

antibody titre profiles (baseline values) of healthy individuals in all the geographical

areas concerned must be determined.

Therefore, this study was undertaken to determine the baseline Salmonella antibody

levels in healthy population in Zaria and eventually establish the significant Widal anti-

O and anti- H titres for a more accurate and reliable diagnosis of typhoid fever using

a single pretreatment Widal test in Zaria, Kaduna State.

1.2       Statement of the Research Problem

Culture of the causative organism, Salmonella enterica serotype typhi is the most

definitive for the diagnosis