From the little I know, dogs can have seizures triggered by any number of things, allergies, stress, epilepsy, etc.
My sister-in-law's malamute mix has seizures that they control with Phenobarbitol. it started with an infection and they really aren't sure if the two are realted or not, but if he doesn't get his medicine regularly he dies have seizures.
I would talk with you vet. See if they can help figure out weather the seizures are being triggered by a medical condition or an outside stimulus, and then how to treat it.