Adult tapeworms cause no apparent harm to their host other than perianal pruritus (itching of the rear end) but that doesn’t make them any less unpleasant!  Owners typically report seeing what looks like rice grains on their pet’s rear end or bedding, or flat worms in the stool. 

The adult tapeworm lives in the small intestine of its host (dogs, cats, and other mammals).  The tapeworm’s body consists of a head segment, a neck, and many tail segments.  The tapeworm’s head attaches to the wall of the intestinal tract and absorbs nutrients through its skin as the food being digested by the host flows past it.  Meanwhile, new tail segments are produced by the neckpiece.  Each tail segment is actually a sac of tapeworm eggs.  These segments/sacs are eventually passed from the host’s rectum into the environment and seen either on the host’s stool or on the host’s rear end. When this sac breaks open the tapeworm eggs are released.  At this stage, these eggs are not infectious to mammals - the tapeworm must reach a specific stage of development before it can infect a mammal. 

Larval fleas that are hatching in this vicinity feed off of organic debris and flea dirt and inadvertently consume these tapeworm eggs.  As the larval flea progresses in its development, the tapeworm inside it is also progressing in development.  By the time the flea is an adult, the tapeworm is ready to infect a dog or cat.   Infection occurs when these fleas are ingested as the pet grooms itself.  Inside the host’s stomach, the flea’s body is digested and the young tapeworm is released.  It finds a spot to attach in the small intestine and the life cycle begins again.

Infection in cats and dogs requires either direct ingestion of an infected flea or ingestion of an intermediate host. An intermediate host would be something carrying the infected flea such as wild rabbits, rodents, birds, etc.  It is possible for humans to develop a tapeworm infection but it would also require ingestion of an infected flea.  Tapeworm infections can be treated with a drug known as praziquantel but controlling fleas is essential to prevent recurring tapeworm infections.

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