DNA-confirmed Taenia solium cysticercosis in black bears (Ursus americanus) from California.

Three cases of cysticercosis in black bears (Ursus americanus) in three northern California counties between 1990 and 1994 have been identified as due to the tapeworm Taenia solium. Both morphologic characteristics as well as the presence of T. solium mitochondria cytochrome oxidase I gene sequences, as detected by the polymerase chain reaction, confirmed the diagnosis. The number and geographic separation of the cases suggests that infection of the bears was not due to a single contamination. Humans infected with the definitive stage of T. solium are the probable source of cysticercosis for bears, as well as other humans. This is the first confirmation of cysticercosis due to T. solium in a black bear in North America.