Compounds of the upper gastrointestinal tract induce rapid and efficient excystation of Entamoeba invadens

The infective stage of Entamoeba parasites is an encysted form. This stage can be readily generated in vitro, which has allowed identification of stimuli that trigger the differentiation of the parasite trophozoite stage into the cyst stage. Studies of the second differentiation event, emergence of the parasite from the cyst upon infection of a host, have been hampered by the lack of an efficient means to excyst the parasite and complete the life cycle in vitro. We have determined that a combination of exposures to water, bicarbonate and bile induces rapid excystment of Entamoeba invadens cysts. The high efficiency of this method has allowed the visualization of the dynamics of the process by electron and confocal microscopy, and should permit the analysis of stage-specific gene expression and high-throughput screening of inhibitory compounds.

[The mucosal changes and influencing factors in upper gastrointestinal anisakiasis: analysis of 141 cases]

BACKGROUND/AIMS

Anisakiasis is a well known parasitosis resulted from eating raw seafoods and there were many reports of cases. However, its endoscopic and clinical characteristics have not been reviewed well. The aim of this study was to clarify the gastric mucosal changes and influencing factors of upper gastrointestinal (UGI) anisakiasis.

METHODS

We analyzed retrospectively the endoscopic and clinical characteristics of 141 cases with UGI anisakiasis diagnosed during UGI endoscopy, based on the review of medical records. The patients' data were collected consecutively from October 1999 through September 2006.

RESULTS

In the 141 patients with UGI anisakiasis, the peak age was the 40s (44.7%). The female to male ratio was 1.82:1. The most prevailed season was winter (41.1%). The most frequent symptom was acute epigastric pain and 76.6% of the patients developed symptoms within 12 hours after the ingestion of raw seafoods. The greater curvature of body was the most preferred site of anisakid larvae. The median time from meal to symptom onset was shortest in esophageal location and longest in fundus location (3 vs. 18.7 hours). The various mucosal changes were observed and the most frequent mucosal change was edema (90.8%). Submucosal tumor was also found in 31.9% of the patients. The severity of mucosal change was related inversely with the time interval from meal to endoscopy (p=0.048).

CONCLUSIONS

Anisakiasis presented various mucosal changes depending on the time interval from ingestion of raw seafood to endoscopy. Delayed endoscopy may lead chronic mucosal change and cause difficulty in the detection of anisakiasis. Therefore, the prompt endoscopic examination is required for the patients presenting acute gastrointestinal symptoms after taking raw fish.