Experimental studies on the pathway for migration and the development of Taiwan Taenia in domestic pigs

The pig is the most favorable experimental intermediate host of Taiwan Taenia. Cysticerci in infected pigs are located in the liver except for a few extrahepatic ones. The present study was designed to investigate the pathway of migration of the oncospheres of Taiwan Taenia in the pig. In the first group, each of 5 Small-Ear-Miniature (SEM) and one Landrace-Small-Ear-Miniature (L-SEM) pigs were injected with 5000 hatched oncospheres into the ear vein. Three SEM and one L-SEM pigs were found to harbor 88 degenerated or calcified cysticerci only in the liver 51-81 days after injection. In the second group, each of 3 L-SEM pigs were injected with 5000 hatched oncospheres into the jugular vein. One of the 3 pigs was found to have 5 cysticerci (2 mature and 3 degenerated or calcified) only in the liver at 89 days post-injection. In the third group, each of 4 SEM, three L-SEM, and 3 L-SEM pigs were injected with 10,000, 10,000, and 5000 hatched oncospheres, respectively, directly into the portal vein after surgical opening of the abdominal cavity. All 10 pigs were found to be infected with a total of 1088 cysticerci (44 mature and 1044 degenerated or calcified) only in the liver 23-62 days after injection. Although the sites of injection in these three groups were different, the liver was the only final location of the cysticerci. These findings give strong evidence that the oncospheres migrate to the liver through the venous circulation and develop in this organ.