Cercarial shedding of Echinostoma cinetoychis and experimental infection of the cercariae to several kinds of snails

이전고환극구흡충(Echinostoma cinitorchis)의 cercaria 유출 및 수종 어류에의 cercaria 감염 실험

The development of Echinestcma cinetorchis in several snail species reared in laboratory aquaria was observed. The eggs from adult cukes collected from the intestine of rats were cultivated to miracidia, and exposed to Hippeutis sp. snails. Observations were made for cercarial shedding from the exposed snails. The cercariae shed from the snails were again exposed to several species of fresh water snails in order to observe metacercarial formation in the snails and their infectivity to final hosts. The results obtained in this study were as follows: 1. Twenty miracidia were exposed to each snail of Hippeutis sp. About 58.3% of the above snails (7 out of 12) were dead before shedding the cercariae, anti the remainder shed the cercariae for a period of 7 to 9 days before death. 2. Cercarial shedding from the infected snails started from the 25th day after the exposure to mi.acidia, and the total number of cercariae shed per snail was 684 in average (range; 482-904). 3. The sixte of refine developed in the infected Hippeutis sp. snails was 1$, 242{\times}214{\;}{\mu}m$ in average, and the number of rediae per snail was 350 in average (range; 120-510). 4. About 40 to 50 cercariae shed from the Hippeutis sp. snails were each exposed to several species of snails reared in the laboratory. The metacercarial formation was confirmed by dissecting the infected snails, 12 to 16 days after the infection. The infectivity to each snail species was 100% in Hippeutis sp. (recovery rate; 56.7%) and Radix auricuzaria coreana (recovery rate; 66.4%), 66.7% in Physa acute (recovery rate; 37.5%), and 50% in Cipangopaludina sp. (recovery rate; 8.0%), respectively. 5. The swimming cercariae attached first at the cephalo-podial part of the snails and then migrated to the mantle, internal organ s and hemocele areas to form the metacercariae. 6. Adult worms of E. cinetorchis were obtained from the rats infected with the metacercariae encysted in the experimental snails. Summarising the above results, it is suggested that the mud-snail (Cipangopaludina sp.) may play an important role as a source of human infection with E. cinetorchis in Korea, and that several species of fresh water snails are involved in the life cycle as a second intermediate host.

실험실에서 사육한 수종 패류를 이용하여 Echinostoma cinetorchis의 생활환을 형성시키 며 발육과정을 관찰하였다. 성충체(흰쥐에서 얻음)에서 분리한 충란을 배양하여 miracidium을 얻고 제 1중간숙주인 Hippeutis sp. 우렁이에 20개씩 감염시킨 바 58.3%(12개 중 7)는 cercaria 유출 전에 감염사하였고 나머지는 25일 째부터 7∼9일간 cercaria를 유출하였다. 이 cercaria를 수종의 패류에 접촉감염(패당 40∼50마리)시켰더니 피낭유충 형성은 Hippeutis sp.에서 100%(접촉 cercaria에 대한 피낭 비율은 56.7%), Radix auricuzaria coreana 100% (66.4%), Phyla acute 66.7% (37.3%) 및 자연산 Cipangopaludina sp. 50% (8%) 감염으로 전 실험 패류가 피낭유충을 형성하였다. Cercaria는 침입시 노출부인 두부, 족부에 부착한 후 포복하여 외투강 내로 이행하며, 패 체내의 피낭부위는 외투막, 원체강내, 내부 기관 및 조직 사이였다. 그리고 이를 흰쥐에 감염시켜 성충을 검출할 수 있었다. 이상의 결과로 한국에 있어서 E. cinetorchis의 주요 인체 감염원 역할을 할 것으로 믿어지는 논우렁이(Cipnngopaludina sp.)에 있어서 피낭유충 형성을 확인할 수 있었고 이 극구흡충은 타종(특히 E. hortense)과 달리 여러 담수 패류가 제2중간숙주 역할을 하고 있음을 확인하였다.