Hello, I'm Dr. Kara. I have over 20 years of experience as a veterinarian and I'd like to help with your concerns about Fudge.
If he is circling and salivating these symptoms usually indicate a disturbance in his vestibular system, or the system that controls balance.
It can signify a middle ear infection or a problem in his brain which "reads" signals from his middle ear. As you can imagine if you're dizzy you wouldn't feel like eating and would make you nauseous, thus his drooling.
It's very important that he continue to eat though. If he doesn't his gut will shut down. If necessary hand feed him or force feed him ground pellets or vegetable baby food several times a day. And drinking when his balance is off will be difficult as well so you may need to help him with that as well.
There are two common reasons for a bunny to lose their balance. One is a middle ear infection with a bacteria called pasteurella, the other is a parasite in the brain called E. cuniculi. Other possibilities, especially in a young, developing bunny are head trauma or inadequate levels of vitamins A & E in their diet.
Bunnies often have the pasteurella bacteria in hiding and in times of stress (as little as change in weather or coming to a new home) it comes out and causes problems. Because bunnies produce inspisated pus (thick, cheesy) he'll need oral antibiotics to effectively penetrate the middle ear and in extreme cases surgery to open up his middle ear and remove the purulent debris.
E. cuniculi is passed bunny to bunny in the urine or very rarely from a mom to kits in utero. If this is his problem he probably had it when you got him. They can shed this parasite in cysts in the urine early in the infection process so if you have kids don't have your children clean his cage and make sure they wash well after handling him. Although it is unlikely he is still passing infectious cysts we should err on the side of caution.
He needs an examination by his veterinarian or a veterinarian that is comfortable treating rabbits. Most veterinarians will treat for both infections if there's any doubt which is present. I usually use Baytril in suspension for the bacteria and a "bendazole" antiparasite drug to treat the parasite. It should be fairly straight forward and treatable if caught early. BUT some bunnies get secondary gut bacterial overgrowth when using oral antibiotics and some are left with a slight head tilt. So sometimes it's not as smooth as we hope.
Your veterinarian can also evaluate him for signs of trauma and discuss diet with you, recommending supplements if they believe he has a deficient diet.
Make sure his cage is kept very clean. Don't use wood chips as bedding though they carry bacteria and fungal spores.
If your veterinarian can see an external ear infection he or she will probably prescribe an ear drop too.
Ideally he would be seen by a veterinarian who is familiar with bunnies very soon. He is young and just doesn't have reserves to draw on. If you don't have a rabbit veterinarian yet here is a link to help you find a rabbit veterinarian in your area: http://www.rabbit.org/vets/vets.htmlBest of luck with your little one. Keep him warm and quiet until you can have him seen.