There are several type of intestinal parasitic worms can infect hamsters. Worms are internal parasites that live inside the body.
Parasites can get into the intestine via the mouth. Transmission is usually, by fecal / oral route. Most often the worms live in the small intestine and do not cause any problems for the hamster. However the hamster may suffer from enteritis and start to lose weight and general condition if there are large numbers of these parasites present. Remember that hamsters practice Coprophagy, and they can re-infect themselves continuously. If you suspect this may be causing a problem see you vet for advice and treatment.
Pinworms in hamsters are less common, they are thought to be harmless..
Hamsters infected with tape worms usually don't usually show any symptoms, but heavy infestations may cause weight loss.