Abstract
Glanders is a zoonotic contagious disease of equids caused by Burkholderia (B.) mallei. Serodiagnosis of the disease is challenging because of false-positive and false-negative test results. The accuracy of the complement fixation test (CFT) which is prescribed for international trade by the World Organisation for Animal Health (OIE), five ELISAs and a Western blot (WB) were compared for serodiagnosis of glanders using sera from 3,000 glanders-free and 254 glanderous equids. Four ELISA tests are based on recombinant antigens (TssA, TssB, BimA and Hcp1), the IDVet ELISA is based on a semi-purified fraction of B. mallei and WB makes use of a purified LPS-containing B. mallei-antigen. Sensitivity and specificity of tests were estimated using cut-off values recommended by the test developers. The WB and all ELISAs, except BimA, were significantly more specific than the CFT. ELISAs based on TssA, TssB, and BimA antigens had significantly lower sensitivity compared to CFT while the sensitivities of the Hcp1-ELISA, the IDVet-ELISA and the WB did not differ significantly from that of the CFT. Given their comparable sensitivities and specificities, the CFT (98.0%, 96.4%), the WB (96.8%, 99.4%), the Hcp1-ELISA (95.3%, 99.6%) and the IDVet-ELISA (92.5%, 99.5%) should be further developed to meet OIE requirements.
Highlights
Glanders is an infectious zoonotic disease of equids, caused by the gram-negative bacterium Burkholderia (B.) mallei
New serological tests have been developed to overcome the disadvantages of the complement fixation test (CFT) i.e. complexity, anti-complementary reactions and poor standardizability [15]. Alternative methods such as the Western blot (WB) and enzyme-linked immunosorbent assays (ELISA) have been applied but have not been fully validated in large-scale studies [5, 9, 16,17,18] according to the principles and methods of validation of diagnostic assays for infectious diseases [19]
To our knowledge, there has not been a comprehensive comparative evaluation study on these diagnostic tests using a suitable panel of well-characterized true-positive and true-negative field sera from different geographical origins. This prospective study compared the diagnostic accuracy of the WB technique, five indirect ELISAs and the Organisation for Animal Health (OIE)-prescribed CFT for the serological detection of B. mallei antibodies in equids
Summary
Glanders is an infectious zoonotic disease of equids, caused by the gram-negative bacterium Burkholderia (B.) mallei. New serological tests have been developed to overcome the disadvantages of the CFT i.e. complexity, anti-complementary reactions and poor standardizability [15] Alternative methods such as the Western blot (WB) and ELISAs have been applied but have not been fully validated in large-scale studies [5, 9, 16,17,18] according to the principles and methods of validation of diagnostic assays for infectious diseases [19]. To our knowledge, there has not been a comprehensive comparative evaluation study on these diagnostic tests using a suitable panel of well-characterized true-positive and true-negative field sera from different geographical origins This prospective study compared the diagnostic accuracy (sensitivity and specificity) of the WB technique, five indirect ELISAs (iELISA) and the OIE-prescribed CFT for the serological detection of B. mallei antibodies in equids. Evaluation of the comparative accuracy of seven assays for serodiagnosis of glanders of animals was known with certainty and in a Bayesian framework, where infection status was considered not known
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