Milk ELISA test accepted for Johne's Disease Negative Status Program
The Milk ELISA test for the diagnosis of Johne's Disease is available to Minnesota dairy producers and is now accepted for the Minnesota Johne's Disease negative status herd program. It is an ELISA test that detects antibodies in milk against the organism that causes Johne's Disease, Mycobacterium avium subsp. paratuberculosis. The test kit being used is ParaCheck® by Prionics (formerly CSL/Biocor).
Milk ELISA testing is conducted by the Minnesota Dairy Herd Improvement Association (DHIA) under the guidance of the University of Minnesota Veterinary Diagnostic Laboratory. Tests cost $6.00 per sample and are charged directly to the producer.
The milk ELISA test can be used by all producers, but will not be subsidized by state or federal funds. The serum ELISA, fecal PCR and fecal culture tests will continue to be available through the University of Minnesota Veterinary Diagnostic Laboratory.
As with all Johne's Disease tests, the milk ELISA test is most effective in detection of infected cows over 36 months of age that are shedding moderate to high levels of the organism. For best results, cows may be sampled any time during lactation except for the first seven days.
Results will be reported as a numerical value indicating the level of antibodies in the sample. Numeric values for the Prionics milk ELISA test are different than values reported for the IDEXX serum ELISA. Numeric values reported for the two tests compare as follows:
| IDEXX serum ELISA (Sample/Positive Ratio) |
Prionics milk ELISA (Optical Density Difference) |
|
|---|---|---|
| Negative test result | < 0.25 | < 0.10 |
| Positive test result | > 0.25 | > 0.10 |
| Positive test result - moderate | > 0.40 | > 0.25 |
| Positive test result - high | > 1.00 | > 0.60 |
Milk ELISA tests for Johne's Disease will be conducted upon producer request using milk samples collected by DHIA. Results from the tests will become a part of the producer's DHIA records and will be reported to the University of Minnesota Veterinary Diagnostic Laboratory and the Board of Animal Health.