ECS auto deploy with ECR
I don't think you can trigger re-deployment based on ECS image being updated. You can however do it as part of your Jenkins pipeline - after you push to ECR as a next step in the pipeline can run a script that will reload the task.

In fact in my pipelines I deploy the ECS Tasks through CloudFormation templates and the CloudFormation stack update is part of the pipeline. That way I update the ECS Task definition automatically every time I push a new image to non-prod ECR. 

Hope that helps :)