Rabbit balance seems to be off

Our rabbit is less than a year old and is eating and drinking normally. What happens is he just flops over on his left side. We take him out of his cage and he runs, jumps normally for a bit, then flops over, always on his left side. I've noticed that he will lean against the wall of his cage as though that is what is keeping him up. A few days ago I noticed he was laying in his cage and was shaking. Any ideas what could be the matter? Thanks for any help you can give.

****Karen Sez****
Hmmm, in aggregate, what you describe sounds very suspiciously like nosema. It is caused by a protozoan parasite named "encephalitozoon cuniculi" and the disease is therefore officially known as 'encephalitozoonosis' (http://www.raising-rabbits.com/rabbit-illnesses.html).

Normally this infection doesn't cause any symptoms at all. The infectious stage lasts for around 3 months and then the rabbit is no longer infectious.

There is no known treatment or cure. If your rabbit's immune system is strong enough to conquer the parasite, I would guess the symptoms might slowly get better, and even go away by themselves, but I have no idea in the case of your rabbit how the course of the infection will go.

A rabbit-savvy vet should be able to find the infective spores in the urine, IF your rabbit is still in the infectious stage, and make a definitive diagnosis, but even so, my resources say there is no known treatment.

Do you have other rabbits? Best to keep THIS one quarantined completely and carefully for around 6 months, until the infectious stage has completely passed.

Best of luck, and God bless you,
K