Sensitivity of test strategies used in the Voluntary Johne's Disease Herd Status Program for detection of Mycobacterium paratuberculosis infection in dairy cattle herds.
OBJECTIVE
To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis.


METHODS
Nonrandom cross-sectional study.


METHODS
64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M. paratuberculosis in feces; the other 8 herds were free from paratuberculosis.


METHODS
For all adult cows in each herd, serum samples were tested for antibodies to M. paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M. paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated.


RESULTS
Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow-up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%.


CONCLUSIONS
Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds.
Wells
Scott J
SJ
Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Whitlock
Robert H
RH
Wagner
Bruce A
BA
Collins
James
J
Garry
Franklyn
F
Hirst
Heather
H
Lawrence
John
J
Saville
William J A
WJ
Naugle
Alecia L Larew
AL
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D015169:Colony Count, Microbial / Q000379:methods / Q000662:veterinary; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D005260:Female; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology* / Q000302:isolation & purification*; D010283:Paratuberculosis / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D015995:Prevalence; D018401:Sample Size; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology
D000907:Antibodies, Bacterial