Melt butter in a Dutch oven over medium heat; add garlic and shallot, and sauté until tender. Add flour; cook 1 minute, stirring constantly. Add clam juice and wine; cook 2 minutes or until thickened, stirring constantly.
Stir in Worcestershire sauce and next 3 ingredients. Cook until thoroughly heated, about 10 minutes. Stir in oysters and crabmeat; cook just until edges of oysters curl.