Biting Victim - what to do?

My 21/2 year old son has been a biting victim for over the past year.  He has come home from daycare with more bites than I can count.  
The assailant is a 21/2 year old girl.  This little girl seems to have only 2 moods, happy or angry.  There are 3 other children in the daycare, 2 older and a one year old.  So far, this girl has not inflicted biting upon the other children other than my son.  I have approached the sitter on a number of occasions and know that my sitter constantly shows the bite marks to the girls parents.  Unfortunately their only belief of discipline is discussion.  They seem to leave the behavioral discipline up to the daycare provider, who would never issue any discipline without approval.
The bite marks are so bad that they are breaking the skin (through sweatshirts and fleece jackets).  My doctor has identified previous bite scars on my sons body.
I have set up a meeting with the girls parents and the day care provider for tonight and am wondering what type of approach and suggestions can be given.  I don't want to sound like I disapprove of their tactics (which I do), but I need to ensure that my son is not harmed again.  Any Advise????

[Kevin Kennedy, Ph.D.]

There should be a firm limit set about behaving in any unsafe way. Children should receive a time out if any unsafe behavior occurs, and they should then (at the conclusion of the time out) be made to play alone for a bit before rejoining the other children. Also, it would be very sensible, even though the children are very young, if parents picked up on the behavior and backed up the discipline of the daycare provider. Talk alone with such young children is pointless - actions speak louder than words. Be sure to inquire about the circumstances under which the biting occurs, and why it is that your son is the only victim. It is the obligation of the provider to protect the children from harm, and the fact that this has occurred repeatedly would make me wonder about the level of supervision. You might want to consider changing the daycare arrangement if the situation doesn't change.