Good evening. Unfortunately, if these are actually maggots you are seeing as opposed to tapeworm segments, which can look similar to the untrained eye, you must bring King to the vet ASAP. The presence of maggots indicates there may be a wound inside or around his anus or rectum that requires veterinary care. It may also mean a cuterebra (botfly) infestation if they have burrowed under the skin. Dewormer of any type isn't going to do anything for him in this case. He must be seen by a vet to determine A. if these are indeed maggots and what type, B. where they are coming from exactly and why they are present, and C. be immediately treated for them and the underlying issue. I've dealt with maggot cases numerous times (much to my chagrin!) and what usually happens is the animal is sedated and the area is shaved and inspected closely. Wounds are cleaned and maggots are flushed out or picked out one by one. I would highly recommend seeing a vet as soon as possible. If he has an infected wound, it will only get worse, and you could potentially lose him. PLEASE let me know how this plays out for you. If I can be of more help, do not hesitate to contact me.
I don't see any open wound but shows there are larva in his winter fur around his anus, since it's so damp around his house, I believed that made his dirty fur the residence of the maggots. I don't see any coming out from his anus now Any advice of any meds to kill these maggots. I am going to shave his winter coat tomorrow. Thanks for the advice.