Double Cheese Pita Pizzas

1 tablespoon extra-virgin olive oil 4 ounces Italian turkey sausage, removed from the casings 2 cloves garlic, grated One 10-ounce package frozen leaf spinach, thawed, squeezed dry and roughly chopped 1 1/4 cups 2-percent cottage cheese 4 whole-wheat pitas, preferably pocketless 1/4 cup thinly sliced red onions (about 1/2 small onion) 4 ounces shredded part-skim mozzarella cheese (about 1 cup) 1/2 cup fresh basil leaves, torn