B. Definitions (pdf)

10.
Interpretation of Individual MV Test Results: (Appendix 4)

a.
A NEGATIVE Individual Maedi Visna (MV)Test Result
For an individual animal test, the MV test is reported as  NEGATIVE if the sheep sampled received a result of NEGATIVE by one of the following diagnostic tests:

i.
A NEGATIVE serological test results as determined by one of the following diagnostic test kits when obtained from an animal health diagnostic laboratory in good repute.

(1)
Elitest – MVV/CAEV (HYPHEN BioMed, Neuville sur Oise, France); hereafter referred to as the HYPHEN Elitest.

The Elitest (HYPHEN) when compared to the CFIA ELISA, appears to have the best agreement and sensitivity based on research conducted by the University of Guelph.

(2)
CAEV/MVV Antibody Test Kits, (IDEXX Laboratories, Hoofddorp, The Netherlands); hereafter referred to as the IDEXX test.

(3)
ID Screen® Maedi Visna Indirect (IDVet Innovative Diagnostics, Montpellier, France)

(4)
Pourquier ELISA Maedi-Visna / CAEV (IDEXX Laboratories)

ii.
Because of inadequate test sensitivity, at this time, results from the following will not be accepted as a NEGATIVE test

Sensitivity refers to the test’s ability to correctly identify all infected sheep as test POSITIVE.  Poor sensitivity leads to many false negative results.  Conversely specificity refers to the test’s ability to correctly identify all healthy sheep as test NEGATIVE. Poor specificity leads to many false positive results.  No test has perfect sensitivity and specificity.

(1)
CAE cELISA (VMRD Inc, Pullman Washington) and

(2)
PCR performed on EDTA blood which detects evidence of the viral DNA in the blood sample and not antibodies.

b.
A SUSPECT Individual MV Test Result.
If, when using any of the tests listed in B.10.a.i., the result is SUSPECT, then the sheep must be either immediately removed or  isolated and re-sampled within 30 days of the test date.  If on re-sample and test,

i.
The test result is NEGATIVE, the individual test is reported as NEGATIVE

ii.
The test result is POSITIVE the individual test is reported as POSITIVE

iii.
The test result is SUSPECT the test is reported as POSITIVE

iv.
The HYPHEN Elitest does not have a SUSPECT category

c.
A POSITIVE Individual MV Test Result.
If, when using any of the tests listed in B.10.a.i. the result is POSITIVE, then the sheep is POSITIVE.

d.
A NON-SPECIFIC Individual MV Test Result

i.
If, when using any of the tests listed in B.10.a.i., the result is reported as NON-SPECIFIC, the sample must be retested by the laboratory using another of the tests listed in B.10.a.i., but the sheep is not resampled.

(1)
A NON-SPECIFIC test result is NOT related to MV infection status but may occur when sheep are immunologically stimulated by another infection or recent vaccination.

ii.
If, on retest the sample can still not be interpreted as either POSITIVE or NEGATIVE by the laboratory, the sheep will need to be resampled and tested.

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