FASCIOLOPSIS BUSKI

Introduction largest intestinal fluke in humans.Infection occurs Fasciolopsis buski is known scientifically as the largest intestinal fluke in humans.Infection occurs primarily in Asia and the Indian subcontinent, especially in area where humans raise pigs and consume freshwater plants, so this helminth is also named as “giant Asian intestinal fluke”.This giant parasite has even been described as “meat worm” or “reddish worm” in traditional Chinese medical book.

I. Morphology (1) Adult Long elliptic, flesh-colored, looks like a slice of raw meat The size: 20-75×8-20×0.5-3mm The ventral sucker (filler-like / infundibular ) is larger and near by the much smaller oral sucker Two coral-liked(珊瑚) testes are located in the posterior half of the body No seminal receptacle

uterus ventral sucker is 3-4 times larger than oral sucker oral sucker cecum ovary vitellaria testes

(2) Egg The thinner shell with an operculum (not so obvious) encloses an ovum and 20-40 yolk cells Slightly yellow in color 130-140×80-85µm (the largest helminth egg) Oval / long elliptic in shape

The first intermediate host： Segmentina

The second intermediate host： Aquatic plant vector water caltrop水红菱 茭白cane shoot Water chestnut荸荠 The second intermediate host： Aquatic plant vector

II. Life cycle Site of inhabitation: small intestine, 2. Infective stage: metacercaria, 3. Infective route and mode: eating raw water plants with metacercariae, 4. Intermediate hosts: Planorbis snail, 5. Reservoir hosts: pig, 6. Life span: 1-4 years, 7. Egg output: 15,000/worm/day.

man eats metacercariae in feces ──────────────────────────── Adolescent Adult Eggs Duodenum In Human Body 3 months are discharged man eats metacercariae in feces on raw water plants ──────────────────────────── Metacercaria Eggs get into water encystations on the In Water 25-30℃ surface of water plants 2-3 months 3-4weeks Miracidia hatch out invades Many cercaria asexual reproduction Planorbis snail Many daughter rediae Many mother rediae Sporocysts

III. Pathology and Symptomatology The enteritis due to worms’ adhesion manifests abdominal discomfort and diarrhea. 2. Malnutrition results from the worms sharing food with the host and diarrhea.

IV. Diagnosis 1. Direct fecal smear, 2. Water sedimentation method Stool examination: 1. Direct fecal smear, 2. Water sedimentation method

V. Treatment and Prevention 1. The treatment of the patients, carriers and pigs Drug of choice is praziquantel. Other effective drugs include hexachloroparaxylene, bithionol (bitin). The drug for pig is dipterex (敌百虫). 2. Prevention (1) Health education (2) Deal with night soil. (3) Avoid feeding pigs on raw water plants

VI. Epidemiology This disease is prevalent in Southeast Asia,China, Japan, Korea, Thailand, Burma, Kampuchea, Vietnam, Bangladesh, Philippines,Indonesia, Malaya and India . In China it is found in 18 provinces, city and autonomic region except north and west regions. The prevalence of fasciolopiasis is relative to growing water plants and feeding pigs on water plants.

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