An infestation of the intestine with the broad tapeworm, Diphyllobothrium, which sometimes causes nausea, malnutrition, diarrhea, and anemia resulting from impaired absorption of vitamin B12 through the gut. The infestation, common in Baltic countries, is contracted following ingestion of uncooked fish infected with the larval stage of the tapeworm. The tapeworm can be expelled from the gut with the anthelmintic quinacrine.