An evaluation of selected screening tests for bovine paratuberculosis

Area of Science:

• Veterinary Immunology
• Bacteriology
• Diagnostic Assays

Background:

• Bovine paratuberculosis, caused by Mycobacterium avium subspecies paratuberculosis, poses a significant economic challenge to the cattle industry.
• Accurate diagnostic tools are crucial for controlling the spread of paratuberculosis in cattle herds.

Purpose of the Study:

• To compare the diagnostic performance of three serological tests: lipoarabinomannan antigen enzyme-linked immunosorbent assay (LAM-ELISA), carbohydrate antigen complement fixation (CH-CFT), and protein D antigen agar gel immunodiffusion (D-AGID).
• To evaluate these tests against histopathology and Mycobacterium paratuberculosis culture from bovine tissues and feces.

Main Methods:

• Utilized samples from cull cows, dairy farms, and serum banks across Ontario, Québec, Pennsylvania, and the northeastern United States.
• Employed receiver operator characteristic (ROC) curves, relative sensitivity and specificity estimates, and kappa statistics for data analysis.
• Compared LAM-ELISA, CH-CFT, and D-AGID against bacteriology and histopathology as gold standards.

Main Results:

• LAM-ELISA demonstrated significantly superior performance compared to CH-CFT and D-AGID.
• LAM-ELISA was more effective in predicting fecal shedding status than detecting tissue infection.
• At a critical optical density of 0.675, LAM-ELISA exhibited 49% sensitivity and 87% specificity relative to bacteriology.

Conclusions:

• While LAM-ELISA is a promising diagnostic tool for bovine paratuberculosis, its current sensitivity limits its ability to accurately predict infection status in individual animals.
• Further research may be needed to improve the sensitivity of LAM-ELISA or explore complementary diagnostic approaches.