While Guillermo del Toro and Carlton Cuse‘s drama The Strain, based on del Toro and Chuck Hogan’s vampire novel trilogy, formally had a pilot order at FX, its series pickup was considered a pure formality. It just came in today. From the onset, when FX landed the project in a bidding war, it hired a full writing staff, with the network committing some $500,000 to creature creation. The Strain now is heading into production on its first season, with the bulk of the scripts already completed and one major casting change. The role of Professor Abraham Setrakian, played in the pilot by John Hurt, is being recast. Filming is slated to begin this month in Toronto for a July premiere. As FX CEO John Landgraf indicated in August, the plan for the series is to run for 39-65 episodes.