Heat a large nonstick skillet coated with cooking spray over medium heat. Add onion, and sauté for 6 minutes or until tender. Stir in spinach, and cook for 2 minutes or until spinach wilts, stirring constantly. Remove from heat. Stir in chicken and the next 6 ingredients (chicken through garlic).
Lightly coat 1 sheet phyllo dough with cooking spray (cover remaining dough to keep from drying). Sprinkle with 1 tablespoon breadcrumbs. Repeat the layers with 3 sheets phyllo, cooking spray, and 3 tablespoons breadcrumbs.
Gently press the layers together. Place about 2 1/2 cups chicken mixture along 1 long edge of top phyllo sheet, leaving a 1/2-inch border. Starting at the long edge with the 1/2-inch border, roll up jelly-roll fashion. Place, seam side down, on a baking sheet coated with cooking spray. Tuck ends under. Repeat with the remaining 4 sheets phyllo, cooking spray, 1/4 cup breadcrumbs, and 2 1/2 cups chicken mixture. Brush strudels evenly with butter. Sprinkle each with 1/8 teaspoon paprika.
Preheat oven to 375°.
Bake strudels at 375° for 20 minutes or until brown. Let stand for 5 minutes before slicing. Cut each strudel into 4 slices. Serve immediately.