MILK – the future of bovine TB testing?
The potential to use milk as a testing substrate for bTB surveillance either at the individual animal level or at the herd level via the bulk tank offers significant advantages. Sampling for individual milk can be performed during milking without a requirement for further handing of the animal, and without the need for trained operators. Furthermore, because such samples are frequently being routinely taken, either during milk recording in the case of individual milks, or in the case of bulk milks, by the processor for payment testing, there is no need for a dedicated visit to the farm to collect the samples.
The Enferplex Bovine TB Antibody Test is a multiplex serological test for bTB. The test is based on a standard indirect ELISA format with two differences: the wells have eleven spots containing antigens present in M. bovis spotted onto the bottom surface of a microtitre plate rather than coated with a single antigen; the endpoint is chemiluminescence rather than colorimetric. We have evaluated the use of bulk and individual milk for the detection of Bovine TB and are awaiting a response from the OIE on our submission for approval.
Relative sensitivity and diagnostic specificity of the Enferplex Bovine TB antibody test using individual milk samples from UK cattle
Likelihood ratio analysis showed a positive LR of 347.8, a negative LR of 0.092, and a diagnostic odds ratio of 3779.1 providing good evidence for infection being present or absent respectively (Caraguel & Colling, 2021).
Correlation of individual Milk with Serum from SICCT test positive animals showed correlation coefficients ranging between 0.76 – 0.96 for individual antigens in the test (P < 0.0001 for all antigens) indicating good correlation between serum and milk results.
Sensitivity and specificity of the Enferplex Bovine TB antibody test using bovine bulk tank milk samples from SICCT positive and bTB free herds
Liklehood ratio analysis showed a positive LR of 348.2, a negative LR of 0.223, and a DOR of 1560.4 indicating good evidence for infection being present or absent respectively (Caraguel & Colling, 2021).
The Enferplex Bovine TB Antibody test
shows high sensitivity and specificity using milk from individual cows and the relationship between serum and milk is highly correlated such that milk could be used as a test substrate in place of serum.Bulk tank milk testing using the highly specific and relatively sensitive Enferplex test would provide an easy, inexpensive and convenient method of screening dairy herds more frequently than is currently the case without causing any disruption.