It may be because the rabbit itself was sick or poisoned, or the cat itself had a compromised immune system which makes it more susceptible to being more vulnerable to any extra harmful bacteria in the prey.
That being said, it is very uncommon for a healthy cat to get sick from eating a rabbit, mouse, rat, bird or other animal it has caught. A cat's digestive system is well equipped for breaking down everything (meat, organ, bone) in order to extract all the nutrients it needs. Even bacteria that can be found has very little to no chance to multiply and become harmful inside the cat as a cat's system is so fast and efficient.
nothing happens to a rabbit when it eats asparagus. no worrys! =)
the evil rabbit
it dies
then you have a big cat
the rainforest bobcat eats cat poo and rabbit vomit
They will die.
puke.
Nothing but they should only have cat food.
He/She will go crazy!!
Will do no harm, I have a cat that eats Dogfish heads.
nothing
A cat eats the elephant