Comparison of three diagnostic methods in detecting brucella infection among slaughterhouse workers at the Kumasi abattoir, Ghana
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Date
2015-11-04
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Abstract
Brucellosis remains neglected in many countries despite its public health importance.
The globally reported number of 500,000 cases per year is likely an underestimation of
the actual figure. In Ghana, there remains paucity of Brucellosis data among high-risk
populations such as slaughterhouse workers.
In hospital setting, laboratory diagnostic methodologies targeting brucellosis is not
performed across Ghana. As a consequence, there is no randomized method with good
specificity and sensitivity to be adopted for routine Brucella diagnostic purposes.
The aim of the study was to evaluate and compare diagnostic performance of Rose
Bengal Plate test, ELISA and PCR used in diagnosing Brucella infection as well as its
prevalence and risk factors associated with the infection among slaughterhouse workers.
A cross-sectional study was carried out at the Kumasi Abattoir with 220 participants
randomly selected. Participants were interviewed about their knowledge on Brucella
using a structured questionnaire. Blood samples were collected and serum extracted. The
samples were tested for the presence of anti-Brucella antibodies using the Enzyme
Linked Immunosorbent Assay (ELISA) and Rose Bengal Plate Test (RBPT). Extracted
DNAs were amplified using the BCSP31-PCR assay.
From the 220 participants tested for antibodies against Brucella spp, 3 (1.4%) were
positive in the Rose Bengal Plate test, 4 (1.8%) were positive in the anti-Brucella ELISA
IgM, 21 (9.6%) were positive in the anti-Brucella ELISA IgG. PCR showed positive for
98 (44.5%) participants.
The sensitivity, specificity, positive predictive value, negative predictive value and
Kappa value for Rose Bengal in comparison with PCR were 66.7%, 55.8%, 2.0%, 100%
and 0.013 respectively while that for ELISA IgG in comparison with PCR were 85.7%,
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71.3%, 18.4%, 98.5% and 0.212 respectively. Most of the anti-Brucella IgG seropositive
(17/21) (OR 2.2; 95% CI 0.6-7.9; p=0.22) and PCR positive individuals (69/148) (OR
1.5; 95% CI 0.8-2.8; p=0.23) were working in the meat-processing unit.
Multivariate analysis showed Odds Ratio but statistically not significant associations for
occupation (OR 1.32; 95% CI 0.64-1.15; p=0.34), assisting in birth of livestock (OR
1.29; 95% C I 0.54-3.11; p=0.34) and use of protective clothing (OR 1.54; 95% CI 0.86-2.76; p=0.147). Education (OR 0.87; 95% CI 0.79-2.19; p=0.284) showed a lower OR
which was also statistically not significant.
The estimated prevalence among those at risk population was 44.5%. PCR method
yielded the highest sensitivity and specificity among the applied methods. This method
is especially helpful epidemiologically in high-risk workers who tested negative for
serologic testing. ELISA method(Mantur et al., 2006) can however be used in cases
where PCR is not available.
Description
A thesis presented to the Department of Clinical Microbiology, School of Medical Sciences, College of Health Sciences, Kwame Nkrumah University of science and technology, Kumasi, Ghana, in partial fulfillment of the requirement for the award of the degree of Master of Philosophy in Clinical Microbiology.