Lack of trust

Question
Thanks for your response. I have followed-up with the vet, and he has confirmed that there is no more pain. He has fully recovered.

In India, there are a lot of stray dogs in the streets. They do not have an owner, and they wander out in the roads all the time.

Is there any special training to ease the mental trauma at this point of time? He is now 2 yrs old.

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Followup To
Question -
I have a Lab, male, 2 years old. 4-5 months back, he was bitten by a stray dog in his neck region, and was badly wounded. I promptly arranged for medical care, and he was cured.

While physically he is fit, I think that incident left a deep depressing memory for him. Because, initially, he loved to be patted in his head and neck. After that incident, he seems to distrust anybody trying to pat him. He even growls at me if I try to pat him. Otherwise, he is still the friendly dog that I knew.

Question: How can I train him to remove the distrust? How can I fully get him out of that traumatic memory?

Answer -
Have you had him back to the vet for follow up visits?  Most dogs really do not like having their head patted, but tolerate it.  Usually they love having the neck, ears, butt and belly rubbed.  I am thinking something there may not be healed up quite right and touching it hurts.  My vet always seems to do a better job finding where the dog hurts than I can.  

If it isn't a physical problem, he may still need more time.  It will be a nuisance.  Most people that come up to a dog want to start patting it on the head and neck.  You will just have to ask them not to.  

It was a real shame that opther dog was allowed to do that.  

Answer
I am afraid I may not have much more help for you.  If you haven't obedience trained him, it could help using positive methods such as praise, treats, or even the clicker to reward him as he learns his commands.  The clicker is a little thing you hold in your hand producing clicks which the dog learns mean approval.  If you do not have classes, there are many good books.  See http://www.dogsbestfriend.com/  You will have to do a search to find material on the clicker training for dogs.