I can see why you are afraid them and want to prevent it from happening again. I'm sure others here have more experience with deworming than I do, so I think it would be a good idea to ask for more opinions on the subject.
Many people, including myself, don't deworm unless they see signs. I haven't dewormed my chickens in many years. If they are kept in a large pen and fed a good diet, it usually isn't needed. If you really think they need the prevention (like if they are confined to a small space) and you...