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Comparison of different testing schemes to increase the detection Mycobacterium bovis infection in Ethiopian cattle
Gobena Ameni1, Abraham Aseffa, Glyn Hewinson
1Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P O Box 1176, Addis Ababa, Ethiopia. gobenaameni@yahoo.com
Insights
Combining diagnostic tests significantly improves bovine tuberculosis (BTB) detection in cattle. Using multiple tests, including the interferon-gamma assay, maximizes the identification of infected animals, crucial for disease control in regions without routine screening.
Area of Science:
- Veterinary Immunology
- Infectious Disease Epidemiology
Background:
- Host immune responses to Mycobacterium bovis (M. bovis) infection vary with disease severity.
- Effective diagnostic tools are essential for bovine tuberculosis (BTB) control, especially in regions like Ethiopia lacking routine screening.
- Cellular and antibody-based tests offer potential for enhanced infection detection.
Purpose of the Study:
- To evaluate the diagnostic performance of single and combined tests for bovine tuberculosis (BTB) in cattle.
- To assess the agreement between different diagnostic methods for M. bovis infection.
Main Methods:
- A study involving 701 cattle tested for BTB using comparative intradermal tuberculin (CIDT) test, interferon (IFN)-gamma test, and lateral flow assay.
- Analysis of apparent prevalence and agreement (Kappa statistic) between test combinations.
Main Results:
- Apparent prevalence ranged from 9-15% (single test) to 23-25% (two tests) and 32% (all three tests).
- Good agreement was observed between CIDT and IFN-gamma tests.
- Poor agreement was found between CIDT and lateral flow assay, and between IFN-gamma and lateral flow assay.
Conclusions:
- Employing multiple diagnostic tests, particularly combinations including IFN-gamma, significantly increases the detection rate of infected animals.
- The findings support the use of combined diagnostic strategies for more comprehensive BTB surveillance.
Abstract:
Host immune responses to Mycobacterium bovis (M. bovis) infection are variable at the different severity stages of pathology of the disease. In countries like Ethiopia, where routine screening of bovine TB is not undertaken, the use of tests which measure cellular and antibody responses may help for the maximum detection of infection. In the present study, 701 cattle were tested for bovine tuberculosis (BTB) using comparative intradermal tuberculin (CIDT) test, interferon (IFN)-gamma test, and lateral flow assay. The apparent prevalence was 32% when all the three tests were used, but varied from 23 to 25% when a pair of tests was used and from 9% to 15% when a single test was used. Agreement was observed between CIDT and IFN-gamma tests both at a cut-off >2 mm (Kappa +/- standard Error, k +/- SE, 0.129 +/- 0.045; 95%CI = 0.041,0.216) and a cut-off >4 mm (k +/- SE, 0.094 +/- 0.044, 95%CI = 0.008,0.179) while no agreement was observed either between CIDT test and lateral flow assay (k +/- SE, -0.04 +/- 0.033; 95%CI = -0.104,0.024) or between IFN-gamma tests and lateral flow assay (k +/- SE, -0.031 +/- 0.032; 95% CI = -0.093,0.031). Thus, the use of more than one test leads to the detection of the maximum number of infected animals.
