Introduction to the Enferplex Test
The Enferplex TB test is a serological assay which identifies the presence of antibody to Mycobacterium bovis, the causal agent of for bovine Tuberculosis (bTB). It has been adapted for use with various species, including cattle, camelids, goats, deer, badgers and pigs. The test detects the presence of antibodies to bTB by use of individual antigens – antigens are parts of the Mycobacterium which generate antibodies which then bind to the antigen. There are seven different TB antigens in the test and these are placed separately as individual spots on the surface of the test well, see figure 1. If antibody to bovine TB is present in the blood sample, then it will bind to the relevant antigen and the resultant reaction produces a luminescent reaction, the light from which can be measured and quantified as a number.
Thresholds are set for each individual antigen spot and if the level of light is above this threshold, a positive reaction is deemed to have occurred. A test where only a single antigen spot reacts to the presence of antibody does not mean that the animal is definitely infected as we see this type of response in animals from TB-free herds and countries. A positive reaction which indicates that the animal is infected is considered to have occurred if two or more of the individual antigen spots react to the presence of antibody (Fig. 2). At this interpretation the test has maximum sensitivity and, in camelids, is 97% specific. As animals respond to more antigens the test becomes more specific until when four antigens are positive the test is above 99.9% specific (Fig. 3).
Figure One: Schematic example of test where one antigen is positive (red) – this result would be interpreted as negative to bovine tuberculosis
Figure Two: Schematic example of test where two antigens are positive – this result would be interpreted as positive to bovine tuberculosis at the two antigen level
Figure Three: Schematic example of test where four antigens are positive – this result would be interpreted as positive to bovine tuberculosis at the four antigen level