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Absorbed EVELISA: a diagnostic test with improved specificity for Johne's disease in cattle
Mary C Scott1, John P Bannantine, Yumiko Kaneko
1Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Foodborne Pathogens and Disease
|August 14, 2010
Summary
A new Johne's disease (JD) test, EVA-ELISA, shows higher sensitivity and specificity than commercial ELISA tests. This improved diagnostic tool uses Mycobacterium phlei antigens to reduce cross-reactive antibodies, aiding in JD control in dairy herds.
Area of Science:
- Veterinary Immunology
- Diagnostic Microbiology
- Dairy Herd Health
Background:
- Enzyme-linked immunosorbent assays (ELISAs) are crucial for Johne's disease (JD) control in dairy cattle.
- A novel ELISA, EVELISA, was developed showing higher sensitivity than existing commercial tests.
- Concerns about cross-reactive antibodies in EVELISA prompted further investigation.
Purpose of the Study:
- To evaluate the performance of EVELISA, particularly addressing false-positive reactions.
- To investigate and mitigate cross-reactivity issues in JD serological testing.
- To compare the diagnostic accuracy of a modified EVELISA (EVA-ELISA) against a commercial ELISA.
Main Methods:
- Serum samples from suspected JD cases and JD-free herds were tested using EVELISA and commercial ELISA.
- Antibody absorption with Mycobacterium phlei antigens was employed to reduce cross-reactivity in EVELISA.
- Sensitivity and specificity were estimated using samples from JD-negative and JD-positive herds (fecal culture confirmed), with Bayesian analysis for further comparison.
Main Results:
- Over 70% of samples from a JD-free herd showed false-positive reactions with the initial EVELISA and commercial ELISA.
- Antibody absorption with M. phlei significantly reduced false positives in EVELISA, classifying only 8 samples as positive compared to 27 by commercial ELISA.
- EVA-ELISA demonstrated high sensitivity (97.1%) and specificity (100%), outperforming commercial ELISA (48.5% sensitivity, 97.4% specificity).
Conclusions:
- Cross-reactive antibodies against environmental mycobacteria contribute to false positives in JD ELISAs.
- The EVA-ELISA, utilizing M. phlei absorption, significantly enhances diagnostic specificity.
- EVA-ELISA offers a more sensitive and specific diagnostic approach for Johne's disease control in dairy herds.
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