I’m sorry your bunny is unwell. I’m not sure what you were reading, but what you stated (i.e. live a full lifetime) is not exactly true. Most bunnies have been exposed to EC at some point. Their immune system will suppress it and the majority will never exhibit any symptoms. So, yes, they can live with EC. A smaller percentage of bunnies will show symptoms of an EC flare. Exactly why this happens is unknown, but for some reason their immune system is unable to fight it off. These bunnies will need treatment to send the EC into remission. Some bunnies will have recurring flares and must be treated more than once. Treatment is Panacur (Fenbendazole), but the dosage and duration are different than if you were using it as a dewormer so it is best to have a vet help you with this. Typical treatment lasts for 28 days.
EC can cause a lot of symptoms, depending on where it is attacking the body. Classic EC is seizures and hind end weakness/paralysis, but this isn’t the case for all bunnies suffering from it. Other symptoms can be the sudden onset of cataracts and incontinence, as you are seeing in your bunny.