Sauté, in hot oil, onion, green pepper, celery and garlic, until tender. Stir in tomatoes and brown lightly. Add paprika, cayenne pepper, Worcestershire powder, sugar, salt, water and bay leaf. Simmer for 15 minutes. Remove bay leaf. Add shrimp, and continue simmering for 10 to 12 minutes more. If desired, thicken sauce with cornstarch slur. Serve over hot rice.