The eggs of this fluke show slightly concave bending of the sides at the operculated end and are about 30 × 16 microns. These flukes are found within the thickened bile ducts and may be present in great numbers. They may invade the pancreas as well as the liver.
These flukes are found in dogs and cats as well as man.
This fluke is supposed to produce most serious symptoms as indigestion, swelling and tenderness of liver, bloody diarrhoea, ascites, oedema and a fatal cachexia.
The course of the disease is insidious and chronic with periodic improvement.
As a matter of fact, many physicians in China attribute very little pathogenic importance to it. The disease is diagnosed by the presence of the ova in the stools. The source of infection is probably through the eating of uncooked fish.
Fig. 117.—Clonorchis sinensis. (Jefferys and Maxwell.)
Kobayashi has examined various molluscs and fish for trematode larvae. He succeeded in infecting nine kittens and two cats by feeding them with certain fresh water fishes whose flesh contained trematode larvae. These fishes were found in districts where human distomiasis was common.
Further experiments by Kobayashi have shown that the larval flukes leave the cyst and start for the biliary passages. When the flukes are very numerous the size is smaller. Maturity is reached in four weeks. This investigator believes that the primary intermediate host is a mollusc as cercariae found in these hosts are very similar to the larval forms found in fish.
He does not consider that there are two species concerned in Clonorchis infections, as he has found variations in continuity of vitellaria in small as well as large flukes. Number of parasites present influences size. Age influences pigment production.