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Relationship between the pathology of bovine intestinal tissue and current diagnostic tests for Johne's disease
Caitlin J Jenvey1, Jesse M Hostetter2, Adrienne L Shircliff1
1USDA-Agricultural Research Service (ARS), National Animal Disease Center, Ames, IA, United States.
Abstract:
Johne's disease is an enteric disease caused by the intracellular pathogen Mycobacterium avium subsp. paratuberculosis (MAP). Upon translocation from the lumen of the small intestine, mycobacteria have the ability to thwart innate defense mechanisms and persist within the macrophage in the lamina propria. In an effort to understand how the pathology of disease is reflected in current diagnostic tests, immunofluorescent (IFA) labeling was performed to quantitate macrophage and MAP numbers in the ileum of infected cattle and correlate results with common methods for diagnosis of MAP infection; including ELISA, IFN-γ assay, RT-PCR, culture of MAP, and histological classification of tissue sections. Predictive models for clinical and subclinical disease states, histopathology acid-fast (AF), MAP location, granulomatous inflammation and type classifications, as well as macrophage, MAP and macrophages with intracellular MAP IFA labeling were successfully developed. The combination of macrophage number and ELISA were the best predictors of clinical disease state, while macrophage number was the best and only significant predictor of subclinical disease state. Fecal culture and number of MAP were the best predictors of granulomatous inflammation, and of combined AF, MAP location and granuloma type, respectively. Additionally, fecal culture and tissue culture were the best predictors of numbers of macrophages and MAP, respectively, while both ELISA and tissue culture were the best predictors of number of macrophages with intracellular MAP.
Insights
Johne's disease diagnostics were improved by correlating macrophage counts and Mycobacterium avium subsp. paratuberculosis (MAP) numbers with various tests. Macrophage counts and ELISA best predicted clinical disease in cattle.
Area of Science:
- Veterinary immunology
- Bacteriology
- Pathology
Background:
- Johne's disease is an enteric infection caused by Mycobacterium avium subsp. paratuberculosis (MAP).
- MAP evades host defenses and persists within macrophages in the ileum.
- Understanding MAP's pathological impact on diagnostic accuracy is crucial.
Purpose of the Study:
- To quantify macrophage and MAP numbers in cattle ilea using immunofluorescent labeling (IFA).
- To correlate IFA findings with standard diagnostic tests for MAP infection.
- To develop predictive models for Johne's disease states and pathology.
Main Methods:
- Immunofluorescent labeling (IFA) to quantify macrophages and MAP in cattle ilea.
- Correlation analysis with ELISA, IFN-γ assay, RT-PCR, MAP culture, and histopathology.
- Development of predictive models for disease states and pathological features.
Main Results:
- Macrophage number and ELISA were top predictors of clinical disease.
- Macrophage number alone predicted subclinical disease.
- Fecal culture and MAP counts predicted inflammation and histopathology.
- ELISA and tissue culture predicted intracellular MAP within macrophages.
Conclusions:
- Integrating macrophage quantification with standard diagnostics enhances Johne's disease prediction.
- Macrophage counts are key indicators for both clinical and subclinical disease states.
- Specific diagnostic tests correlate with distinct pathological features of MAP infection.