Sounds like a maggot.  take her back where u purchased her & ask if she has been de-wormed and get the documentation proving it. Then take pup where the documentation says procedure was done and tell them what happened after your dog's bowel movement.♥

 Roundworms and tapeworms are two of the most common worms in puppies.  Roundworms typically are longer and look more like spaghetti, while tapeworms are segmented and often each segment is shed separately--often looking like a grain of rice.  Tapeworms are smooth, often found in the stool and around the rectum; they move around a lot. Intestinal parasites are common in puppies and 2 dewormings are part of normal puppy care.
Fleas are involved in tapeworm transmission-they transmit the worm when the dog eats an infected flea from themselves or mom.  The puppy should be started on a flea and tick preventative.
Maggots are fly larvae that grow in diseased or infected tissue.  If there is no wound or infected area on the puppy or around the anus then it is not a maggot.  Maggots are usually found in large amounts on the skin near a wound, they are not defecated out individually.
Your puppy needs to be examined by a veterinarian and a fecal exam needs to be run to see what types of worms your puppy has.  Bring the worm from the stool for a visual identification if possible.
Good Luck!

 You need to get the dog some dewormer meds. That you can get t a pet store or walmart. The dog probably was given human food and that will give them worms they need to be deformed every month if given human food on the bottle it will tell you directions .

 Well take her or him to the vet its probaly worms

 Have you taken your puppy to the vet? If not. It was probably giving a deworming med by the previous owner. It's common for puppies to have hookworms, roundworms, and tapeworms. But beware of heartworms if not tested you never know if puppies or dogs have it until it' s to late. Here's a link for your info. petcaretips.net Having a animal is like take care of a child. Maybe not a good example. But they need their shots and annual check-ups. Take care of it.

 Yes!  Do get your puppy dewormed.  You may also notice your dog dragging it's bottom on the carpet to try and scratch the itchy feeling it gets from the worms.  This will spread the worms on your carpet so I hope you do not have SMALL children on that carpet!

 I think they are all right and she/he has got worms good luck in getting rid they are not nice

 This is a tapeworm usually from fleas.  When they are biting at the fleas they swallow them and in return get tapes.  Tell the vet there are little rice like beings around the rectum and he will give you med (it is usually a pill depending on size)  Must get rid of fleas or you will go thru this often.  Be careful because over the counter meds are hard on puppies.