Many rabbits are exposed to EC sometime during their life (even before birth), but symptoms may or may not develop during the rabbits lifetime. The immune systems of rabbits may keep the infection under control. Other rabbits with EC that come under stress (physical or otherwise) may develop symptoms ranging from seizures, cataracts, weakness, paralysis, head nodding, uncontrolled eye movements, behavioral changes, or head tilt.
I have a rabbit who had violent seizures over a 24-hour period. I suspected EC and the test came back positive. She was on panacur for 4 weeks and symptoms have not returned.
What medication did they give you? If the rabbit resists taking the medication it sometimes works to put it on a piece of banana or other favored food.