Upto 50% of rabbits have this and it causes neurological symptom like head tilts,catarracts, kidney disease and many other problems. The best drug is Fenbendazole mixed with aniseed given daily by mouth for 28 days called Lapizole.
You will never cure your rabbit but can stop it spreading the parasite to other rabbits. The cheapest way to treat your rabbit is to use 10 per cent fenbendazole called Panacur from the vet. They do make a panacur paste for rabbits but it is a bit more expensive.