Boil shrimp in salted water for 5 min.; save stock. Clean shrimp and set aside. Cut okra into thin rounds and brown in shortening. Do not scorch. In another pan, make a roux with flour and shortening. Add garlic and cook until golden brown. Add onion, bell pepper, celery and parsley. Cook until transparent. Add tomato sauce, simmer 10 minutes. Stir in shrimp stock and blend well. Add thyme and bay leaves, cook 1 hour. Last 20 minutes, add shrimp, crab, salt, pepper, Tabasco sauce, Worcestershire sauce and okra. Cover pot and allow to simmer gently at least 1 hour.