Proceedings of the 10th International Colloquium on Paratuberculosis

RESULTS
Of <strong>the</strong> 327 fecal specimens analyzed by all three techniques, 22 animals were identified as
heavy shedders based upon <strong>the</strong>ir fecal culture results.
Of <strong>the</strong> 22 heavy fecal Map shedders identified by fecal culture results alone, 7 fecal
specimens had corresponding confirmative real-time and nested PCR tests, 5 specimens
had ei<strong>the</strong>r a positive real-time or nested PCR test. Ten fecal specimens (45%) failed to be
confirmed by ei<strong>the</strong>r <strong>the</strong> corresponding real-time or nested PCR tests (Table 1).
Of <strong>the</strong> 6 cows with positive correspondence between fecal culture, real-time PCR, and
nested PCR, 4 were culled. Two had diagnostic ELISA titer at <strong>the</strong> time <strong>of</strong> <strong>the</strong>ir removal from
<strong>the</strong> herd. Of <strong>the</strong> remaining two cows, one cow had an initial high suspicious titer as
determined by ParaChek® Map ELISA testing that subsequently corrected. The o<strong>the</strong>r cow
had no evidence <strong>of</strong> having had a serological response.
DISCUSSION
The three methods used to identify Map required separate test samples being taken from a
given fecal specimen. The concurrence <strong>of</strong> all three tests decreases <strong>the</strong> probability <strong>of</strong> sample
error due to clumping; whereas non-concurrence between <strong>the</strong> three tests argues for nonuniform
distribution <strong>of</strong> organisms.
The importance <strong>of</strong> correctly identifying heavy fecal shedding <strong>of</strong> Map is two-fold:
1) animals identified as heavy shedders are considered to be primary disseminators <strong>of</strong>
pathogenic mycobacterium into <strong>the</strong> environment; and
2) heavy Map replication in feces documents advanced mucosal disease and increased
probability <strong>of</strong> systemic progression.
The lack <strong>of</strong> concurrence between a positive fecal culture and two sensitive PCR tests puts
into question <strong>the</strong> designation <strong>of</strong> “heavy or moderate shedding” as identified by <strong>the</strong> culture. It
argued that fecal culture results can be significantly colored by sampling error.
CONCLUSION
Forty-five percent <strong>of</strong> <strong>the</strong> cows identified in this study as heavy shedders by Trek® Diagnostic
System were documented by real-time and nested PCR to be light fecal shedders. Decision
makers may be well advised to seek additional confirmation <strong>of</strong> fecal heavy shedding status
before culling an animal from <strong>the</strong> herd based upon this criterion alone.
REFERENCES
Collins M.T., Gardner I. A., Garry F. B., Roussel A.J., Wells S.J, 2006. Consensus
recommendations on diagnostic testing for <strong>the</strong> detection <strong>of</strong> paratuberculosis in cattle in
<strong>the</strong> United States. JAVMA, 229, 912-919.
Harris N. B., Barletta R. G.: Mycobacterium avium subsp. paratuberculosis in veterinary
medicine. Clin. Microbiol. Reviews 2001; 14:489-512.
ACKNOWLEDGEMENT
The authors acknowledge <strong>the</strong> gracious collaboration and support received from <strong>the</strong> Florida
Department <strong>of</strong> Agriculture and Consumer Services and <strong>the</strong> United States Department <strong>of</strong>
Agriculture.
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