A woman walking her partner's guide dog were attacked by another dog in Northampton, police said.
The guide dog needed stitches after it was attacked from behind in Park Avenue North, near the junction of Elmhurst Avenue.
While trying to stop this, the woman was bitten on the hand and sustained two puncture wounds.
The offending dog is described as a large, Akita-type dog with long, fawn coloured fur and a long tail.
Several members of the public stopped to help and police officers are now asking them, or anyone who witnessed the incident on February 28, to get in touch.
Witnesses can contact police on 101 or Crimestoppers anonymously on 0800 111 555.