Police are investigating incident which happened on Brookhouse Lane, Featherstone. at 5.20pm on Sunday and involved a 15-year-old.
The dog has been placed in specialist kennels whilst Staffordshire Police investigate.
Any witnesses to the attack can call 101, quoting incident 557 of 28 May or message police using the live chat facility at www.staffordshire.police.uk
To report anonymously, they can call Crimestoppers on 0800 555 111.