The tapeworm is a parasite spread among cats, dogs, and people through the ingestion of infected fleas. It's more common in cats and less in other pets or people. 

How it is spread : When a person and particular dog swallow an infected flea, it usually gets infected with the tapeworm. Nevertheless, providing appropriate treatment to pets for fleas can prevent and even reduce the risk of this infection.  

Who is at risk : People are at very low risk of getting infected with tapeworm. However, infants or children are more prone to exposure to this disease. 

Signs in dogs : Tapeworms are sometimes not harmful to dogs and don't cause any illness. One can detect the parasites crawling near the anus or in fresh feces (poop). In case of serious infection, dogs may start losing weight. 

Symptoms in people : This infection is not very common in people, and there are no symptoms.