Motility Of Intestinal Fluke, Echinostoma Spp, Metacercariae In Fish Dishes Prepared By Different Uncooked Methods

Abstract

Fish-borne trematode is a worldwide problem. In addition to the major liver flukes, several types of intestinal flukes also use minnows as the intermediate host. Traditional ingestion of undercooked and uncooked fish preparations is a major factor in pathogen acquisition. Several freshly killed freshwater fish, Cyclocheilichthys armatus, were purchased from the local market and sent to the laboratory to be examined under a stereoscopic microscope for active Echinostoma spp metacercariae. A total of 10 fish were infected with many active metacercariae and used in the preparation of uncooked fish dishes: 1) left to dry at room temperature; 2) frozen; 3) refrigerated; 4) marinated in saline; and 5) marinated in 5% acetic acid solution. The motility of the metacercariae in each of these dishes was examined under a stereoscopic microscope. Motility was estimated as the level of activity or degeneration of the metacercariae at the start of the experiment and then every 30 minutes until all the parasites appeared degenerate (and therefore, presumably not viable). Degeneration of the parasites was slowed by cooling: degeneration of all metacercariae took approximately 10 hours in the refrigerated or frozen fish, compared with 4 hours in all other dishes left at room temperature. Of interest, this period is longer than reported times for the metacercariae of the intestinal flukes in recent published works. In conclusion, the studied uncooked preparation mimicking the traditional practice cannot induce degeneration to the contaminated metacercariae of in the short period. Since the real practice of the Thais is rapidly eating after preparation, hence, the active strategy to change this rooted behavior is necessary.