Antibodies to E cuniculi in rabbits can be detected on a blood test. Hence, a rabbit that has been infected by E cuniculi will produce antibodies that will produce a positive test.
However, some rabbits appear to clear the infection completely and over time their blood test will become negative again.
Have or have not
Until recently, tests available in the UK could not distinguish between current and past infection. A negative result basically ruled out E cuniculi as the cause of illness but a positive result only told you the bunny had been infected at some point in time, and did not help to determine whether the infection was recent and ongoing.
However, quantitative tests that can actually measure the levels of antibody in the blood sample (not just whether they are there or not) are now available in the UK, introduced by Medlab in Cheshire.
By testing two separate samples (taken with an interval between them) it is now possible to determine if a rabbit is mounting an immune response to an active E cuniculi infection.