You must get it to drink water as will become dehydrated..is it eating? will it eat? if so mix water with food and put near it. Use something to be able to get near the dog, like a tennis racket to protect yourself and don't retreat, stand firm and inch forward until it surrenders, then take to the vet as quickly as possible, or get help from someone close by who can do this. That's all I have.
Get Brexit done.