Worming of rabbits is advised due to the risk of Encephalitozoon cuniculi. This is a common parasite spread in urine, affecting primarily the nervous system and kidneys. It often results in neurological signs (such as a head tilt or circling) or hindlimb weakness and paralysis.
Worming treatment slows the rate of multiplication of the parasite within the body, and can be performed either as a treatment if E.cuniculi is suspected, or prophylactically.