Anas domestica as a definitive host and Ophicephalus argus as a second intermediate host of Clonorchis sinensis.

The natural infection of Clonorchis sinensis has been noted widely among carnivorous mammals such as human, dog, cat and weasel etc. This infection is experimentally reproducible in rabbits and guinea pigs together with a number of other mammals, while there remains a great deal to be discussed as to whether a certain species of birds can be a definitive host. The infection of Clonorchis sinensis in birds was first observed by J. Asada (1920). He examined 6 Nycticorax nicticorax and found in one of them 13 pieces of Clonorchis sinensis infesting on its gall bladder, and the flukes were found to accomodate eggs containing perfectly developed miracidium in their uterus and their ovulation was found to be quite active. Pseudorasbora parva was experimentally fed to several Nycticoyax nicticorax. They were sacrificed 45 days later and 5 pieces of Clonorchis were found upon dissecting though small in size. At the same time, he fed Anus domestica with Carassius auratus and Pseudorasbora and found 7 pieces of Clonorchis sinensis infesting on the gall bladder in one of them. He reported, however, that their sizes were smaller in comparison with those usually found in the other hosts. On the other hand, H. Tanabe (1920) reported that an attempt of experimental infection of Anus domestica and Anas boschas with Clonorchis sinensis was not successful. Similar experimental infection tried on 9 Egretta sp. showed the flukes, in a very early stage of the development, infest sporadically in their coecum and large intestine but the majority of them were found already dead and on the way of excretion. Shanghai area in China has been known as an endemic area of Clonorchis sinensis. Stool examination of Japanese residents (restaurant employees) were performed in 1935 by Komiya, Kawana and Tao. The ova of Clonorchis sinensis were found to be present in approximately 21%