Dog used to be submissive towards new dogs, now aggressive

Question
My 3 year old female Boxer/Lab mix was adopted as a very submissive dog. She was always very friendly and playful when meeting other dogs and has over a dozen dog friends she plays with every week. We frequented the dog park and live in an area with many dogs who walk with their owners off leash. Maybe 6 months ago, she was attacked on our bike trail by another dog... she kept on and the other dog pursued her and punctured her leg. Soon after, she started with leash aggression. Now, she sees a new dog, they sniff, her spine gets real stiff and her ridge lifts up and then as the other friendly dogs move away, she puts her paws on their back and lets out loud aggressive snarls that spook the other dogs/owners. It as if she is expressing her dominance constantly.

This said, what is the proper rehabilitation to get her to be friendly to new dogs rather than resort to her dominance. Should we leash her when meeting new dogs to show our control of the situation? We're so confused since this used to never be an issue and she isn't aggressive in any other aspect of her life.

Thanks for any help! She is a total angel (of couse I'd say that) and we want to keep her that way in and outside of our home.  

Answer
Hi Courtney,

Thank you for writing to me. I apologize for the delay in responding but I've been sick with the flu.  Thank you for your patience.

I am feeling so badly for your situation.  When a dog is attacked, it sometimes causes a condition known as fear aggression.  It is imperative that you work with a trainer/behavorist in desensitizing your dog to other dogs and showing your dog that not all dogs are going to be a threat...through the use of positive reinforcement and desensitization. Speak to your vet about referrals or if you are located near a teaching vet school (they are listed on line) they often have a department for behavorial science.  There are also many books and tapes that are available written and produced by some of the best trainers in the world.  My favorite source is dogwise.com/  

There is also a section of allexperts dealing with canine behavorial issues and I urge you to consult with these volunteers.

In the meantime, it is imperative to prevent any further altercations from occuring until you start working with an expert in the field.  If it takes leashing or avoidance, changing direction to avoid a situation etc, it must be done.  I would also urge you to carry a product that will give you control over any future situations so you can protect your dog. The one I prefer is called HALT.  I've also used a jet stream spray bottle of pure vinegar.  Either one will give you an edge on the situation and will also give you confidence, which your dog will respond to.

I wish you the very best of luck and may the new year look more promising for your situation!

Regards,
Shelley Davis