Fig. 161.—Clonorchis endemicus: eggs. The knobs on the eggs are not shown. × 900. (After Looss.)
Verdun and Bruyant deny, in opposition to Looss, the possibility of being able to distinguish within the genus Clonorchis the two species described, but they admit the justification for the new genus. They also report the occurrence of Opisthorchis felineus in man in Tonkin (Compt. Rend. Soc. de Biol., lxii, 1907).
Pathology.—Both species of Clonorchis give rise to grave symptoms. The liver is generally enlarged, though when the infection has lasted some time it begins to contract. The surface of the organ is studded with white vesicles, and on cutting into it one sees numerous cavities with thickened walls (distended bile-ducts) filled with a brownish fluid containing innumerable eggs, which cause its colour. Microscopically, the epithelium of the bile-ducts is either (1) entirely destroyed, or (2) actively proliferates, forming an adenomatous outgrowth. Occasionally this proliferation is not limited by the wall of the bile-duct but penetrates it and leads to a growth of numerous new ducts, forming a malignant biliary adenoma. The bile-ducts have their connective tissue wall greatly sclerosed. These fuse with one another, forming areas of sclerosis devoid of liver tissue. As a result of these changes the liver cells atrophy and undergo fatty pigmentary and granular degeneration. Besides these changes, due probably to the toxic action of the flukes, mechanical obstruction due to the actual plugging of the ducts by the flukes causes retention of bile and icterus, and through pressure on veins, ascites and hypertrophy of the spleen.
To what extent blood or bile respectively forms the food of the flukes is uncertain.
Life-history.—(Kobayashi, 1911, Mitteilungen aus dem kaiserlichen Institut für Infektions-Krankheiten zu Tokio, pp. 58–62.)
It results from the work of Kobayashi in Japan that fresh-water fish form the second intermediate host for Clonorchis endemicus. He fed cats with encysted flukes (cercariæ) from various fish and easily succeeded in infecting them, e.g. a kitten, proved to be uninfected by repeated examination of its fæces, was fed on infected fish; a month later innumerable flukes were found in the bile-ducts, gall-bladder, pancreas and even in the duodenum. The fish infected were Leucogobis güntheri, Pseudorasbora parva, and to a less extent Acheclognathus lanceolata, Acheclognathus limbata, Paracheclognathus rhombea, Pseudoperilampus typus, Abbottina psegma, Biwia zezera and Sarcocheilichthys variegatus. The cysts occur throughout the muscles and subcutaneous tissue of the fish. Length 0·13 mm., breadth 0·1 mm. The cercaria lies folded in the cyst, length 0·5 mm. breadth 0·1 mm. It tapers posteriorly. Skin at first covered with fine spines, disappearing as they grow older. Body dotted with fine pigment.
The first intermediate host is still unknown.
Sub-family. Metorchiinæ, Lühe, 1909.
Genus. Metorchis, Looss, 1899, emend. auctor.
Hind end rounded. Gut forks reach extreme end. Testes only slightly lobed, filling the hind end.