Abstract
BackgroundBovine tuberculosis (bTB) is prevalent in dairy cattle in Ethiopia. Currently used diagnostic tools such as the single intradermal comparative tuberculin test (SICTT) are time consuming and labor intensive. A rapid, easy-to-use and cost-effective diagnostic test would greatly contribute to the control of bTB in developing countries like Ethiopia. In the present study, two point-of-care diagnostic tests were evaluated for the detection of bTB: LIONEX® Animal TB Rapid test, a membrane-based test for the detection of antibodies to Mycobacterium bovis in blood and ALERE® Determine TB Lipoarabinomannan (LAM) Ag, an immunoassay for the detection of lipoarabinomannan (LAM) antigen (Ag) of mycobacteria in urine. A combination of the SICTT and gamma interferon (IFN-γ) test was used as the gold standard for the validation of these point-of-care tests, as it was not feasible to slaughter the study animals to carry out the historical gold standard of mycobacterial culture. A total of 175 heads of cattle having three different bTB infection categories (positive SICTT, negative SICTT, and unknown SICTT status) were used for this study.ResultThe sensitivity and specificity of TB LAM Ag were 72.2% (95% CI = 62.2, 80.4) and 98.8% (95% CI = 93.6, 99.7), respectively, while the sensitivity and specificity of the LIONEX Animal TB rapid test assay were 54% (95% CI = 44.1 64.3) and 98.8% (95% CI = 93.6, 99.7) respectively. The agreement between TB LAM Ag and SICTT was higher (κ = 0.85; 95% CI = 0.65–0.94) than between TB LAM Ag and IFN-γ (κ = 0.67; 95% CI = 0.52–0.81). The agreement between LIONEX Animals TB Rapid blood test and SICTT was substantial, (κ = 0.63; 95% CI = 0.49–0.77) while the agreement between LIONEX Animal TB rapid blood test and IFN-γ test was moderate (κ = 0.53; 95% CI = 0.40–0.67). Analysis of receiver operating curve (ROC) indicated that the area under the ROC curve (AUC) for TB LAM Ag was 0.85 (95% CI = 0.79–0.91) while it was 0.76 (95% CI; =0.69–0.83) for LIONEX Animal TB rapid test assay.ConclusionThis study showed that TB LAM Ag had a better diagnostic performance and could potentially be used as ancillary either to SICTT or IFN-γ test for diagnosis of bTB.
Highlights
Bovine tuberculosis is prevalent in dairy cattle in Ethiopia
This study showed that TB LAM Ag had a better diagnostic performance and could potentially be used as ancillary either to single intradermal comparative tuberculin test (SICTT) or IFN-γ test for diagnosis of Bovine tuberculosis (bTB)
The area under receiver operating curve (ROC) curve (AUC) of TB for TB LAM Ag test was 0.85 (95%confidence intervals (CI) = 0.79–0.91) while it was 0.76 (95%CI; =0.69–0.83) for the LIONEX Animal TB rapid blood test (Fig. 1). In this preliminary study, diagnostic performance of the TB LAM Ag urine test and LIONEX Animal TB Rapid blood test was evaluated using the combined result of SICTT and IFN-γ test as a gold standard
Summary
Bovine tuberculosis (bTB) is prevalent in dairy cattle in Ethiopia. A rapid, easyto-use and cost-effective diagnostic test would greatly contribute to the control of bTB in developing countries like Ethiopia. Two point-of-care diagnostic tests were evaluated for the detection of bTB: LIONEX® Animal TB Rapid test, a membrane-based test for the detection of antibodies to Mycobacterium bovis in blood and ALERE® Determine TB Lipoarabinomannan (LAM) Ag, an immunoassay for the detection of lipoarabinomannan (LAM) antigen (Ag) of mycobacteria in urine. In Ethiopia, studies have shown that there is a widespread but variable occurrence of bTB throughout the country based on cattle breed and dairy farm conditions [4, 5]. The same review showed higher prevalence (16.6%) in intensive farms as compared to low prevalence (4.6%) in extensive farms
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