
Sudden changes in behaviour should really be addressed first with your vet - although there is every possibility this is resource guarding (food or any other "prized" possession) it is better to have any possible medical reasons ruled out whether obviously physical (mouth/neck/joint pain for eg) or neurological issues.
There are a few MUST do's and MUST don'ts to observe and you really need to be on the ball here!
Let's looks at the
Do's :)
1. See a vet, have her thoroughly checked over and see if further tests are required.
2. Assuming a clean bill of health, seek a veterinary referral to a reputable behaviourist
3. Put three or more small bowls of food down, spaced well apart, when the dog is to be fed. "Drop" a little food in each bowl from it's daily ration - as the dog eats from one it will see and hear you adding to another. It should over time develop a realisation that you around a food bowl = good, extras coming.
4. When the dog has something in it's mouth, toy, food (laundry! :-D ) offer a "SWAP" to the dog with something of higher value - i.e. it has kibble, offer cheese; it has cheese, offer roast chicken; it has toy, offer dog biscuit/treat or a more exciting toy; it has laundry or similar stolen item, offer something more rewarding (probably food)
4. Lay out some basic ground rules for the family as well as the dog and ensure they are stuck to rigidly until professionally advised otherwise
here come the
DONT'S :) 1. Ensure that your children
neverleave a crumb of food lying around - EVER.
2. Don't allow the dog to remain in the room where you are preparing and eating food - no matter how inconvenient.
3. Don't permit the children to feed the dog or interact with the dog when there is food around - theirs or the dog's
4. Dont permit the children to take anything from the dog or pre-emptively rescue something it's about to take
5. Don't take your eye off this dog for a second until remedial training is showing sound progress
The fact that warnings have escalated so far that this dog is now biting IMO lays bare the fact that family actions should have been addressed much more quickly than now and also that advice should have been sought much sooner too. However much of that is a moot point as the fact is that things have escalated so please follow the guidelines above plus any other sensible precautions until such times as professional advice with someone who has examined and observed the dog closely has been gone through. This is a young dog and, barring serious medical problems, this behaviour can be turned around but it needs dedication, commitment and by the nature of the dog's reactions, outside expertise.
There are some very experienced folks on here who doubtless will be able to add to the above.
I hope this helps a little meantime.
Best wishes, Teri