How can you get rid of fleas on a Mongolian gerbil?

I was watching my gerbil run around is cage. While I was watching him he started scratching his ears and head area. Then I saw him biting his side. I saw something black that looked like a flea on his head. He is totally black and has a white spot on his neck and that is where I saw it. So how am I supposed to get rid of them? Can they kill my gerbil or do they just make him itch like any other animal? I have never had this happen before.