This is from the IGCA
(Italian greyhound club of america) about helath concerns in the breed.
"Idiopathic epilepsy is another condition which affects IG's. Otherwise healthy dogs begin having seizures at 2-5 years, and no cause for the seizures can be identified. In many cases, the seizures are mild and infrequent, and no treatment is necessary. If the seizures become violent, more frequent, or occur in "clusters" the veterinarian will recommend the dog be placed on anticonvulsants. Phenobarbital is currently considered the drug of choice, and is widely used in IG's. Phenobarb (as it is known) is a member of the barbiturate class of drugs, but given orally is as safe in IG's as in any other breed.
In every breed in which research has been undertaken, idiopathic epilepsy has been determined to be an inherited disease. It is not recommended to breed an animal that has seizures."
It doesn't give you numbers as to the occurance of this problem in the breed unfortunately. You may want to message some of the breeders in the club and see what their opinion is on how prevalent it is.