JMHO, ..In my experience with EC ,
EC is not detectable in "healthy breedstock" without a very expensive blood test , and that test is not reliable, as it just shows exposure [titer count] .
Working at a "shelter" I had extensive experience treating the EC symptoms - and several drugs were effective to varying degrees .. however , ... no drug "cured" EC effectively .. Rabbits would always need to be treated again sometime at a later date... [arguably,.. the rabbits at the shelter could have been reinfected by other rabbits showing no symptoms]
The drugs used, seemed to me, to be effective for controlling symptoms, and stopping the further spread of the disease .... [if caught early, some mobility could be restored]
I have had limited experience with EC in my rabbits, with only one rescued doe with EC . She showed no symptoms, but some of her kits would be born with either "EC eye" or "early onset" rear end paralysis. Garlic chives, were at least as effective as "the drugs".
But,... just like when I tried EC drugs, a few months after I stopped feeding garlic chives, the symptoms in the young kits reappeared. The doe at my farm was in a "quarantine" section, so she would not have been reinfected after treatment. The Doe referred to, never showed any symptoms at all, throughout her entire life...