Sofia, Bulgaria - June 21, 2016: An assistance dog is shown during a performance before given to an individual with a disability. The animal is trained by an assistance dog organization with the help of a professional trainer. - Stock Photo & Image

An assistance dog is trained to aid or assist an individual with a disability. Many are trained by an assistance dog organization, or by their handler, often with the help of a professional trainer.

Sofia, Bulgaria - June 21, 2016: An assistance dogs are shown during a performance before given to an individual with a disability. The animal is trained by an assistance dog organization with the help of a professional trainer.

An assistance dog is trained to aid or assist an individual with a disability. Many are trained by an assistance dog organization, or by their handler, often with the help of a professional trainer.

Man with disability with his service dog using electric wheelchair.

Man with disability with his service dog using electric wheelchair.

Service dog giving assistance to disabled person on wheelchair.

Man with disability with his service dog using electric wheelchair.

Service dog giving assistance to disabled person on wheelchair.

Vienna, Austria - May 1, 2015: A bus driver helps physically disabled person in a wheelchair to board in the bus.

Vienna, Austria - May 1, 2015: A bus driver helps physically disabled person in a wheelchair to board in the bus.

An assistance dog is trained to aid or assist an individual with a disability. Many are trained by an assistance dog organization, or by their handler, often with the help of a professional trainer.

An assistance dog is trained to aid or assist an individual with a disability. Many are trained by an assistance dog organization, or by their handler, often with the help of a professional trainer.

Customs officer and his dog are participating in a training for drugs detection in Sofia's airport. The dogs are trained to find drugs smuggled in the luggage.

A blind person is led by her golden retriever guide dog during the last training for the dog. The dogs are undergoing various trainings before finally given to the physically disabled people.

Physically disabled people in wheelchairs in a basketball hall.

Sofia, Bulgaria - December 18, 2015: A dog is being prepared by a nurce for an operation in a veterinary clinic. The surgery is skin-grafting sfter the dog was injured in a dog fight.