It is widely believed that over half, and possibly up to 80%, of rabbits carry E. cuniculi.
It is usually spread when rabbits lick the urine of other rabbits. This is extremely common behavior, and will occur with a doe and her litter, as there will be urine residue on the cage wire. It can also spread this way if either a doe or buck urinates while they are together for breeding.
Head tilt can be caused by other things besides E. cuniculi. Since your rabbit has not gotten any worse, she may have one of the other causes... like an inner ear issue or infection.
I have a rabbit now with wry neck. He was our herd sire, but also my son's pet. For this reason, he is now an inside pet bunny. His head is still tilted 90* from vertical, but he's learning how to make do. He's had a long road, and we almost lost him a couple of times. Once early on to the wry neck, once just a week or two ago to moldy feed. He can't hop yet, but he can move around, eat and drink on his own. He flops over for you to pick him up, and loves to sleep in your lap. He keeps himself clean, too.
The only reason we have worked so hard to save him, though, is that it was my fault -- I changed his water bottle, and he got dehydrated as a result. This gives E. cuniculi a favorable environment to become active. Also, because this was my son's other pet rabbit. The first died of wool block. Both of my daughter's bunnies are still alive. I really didn't want him to lose his other bun. And he's having a marvelous time holding his bunny all the time now.
I would not recommend such a course of treatment for any but a cherished pet, though, and even then it may be better to put the rabbit down.
In your case, I really wonder if it is E. cuniculi, though.
