Egg hatches to free-swimming miracidium in 3 weeks. Miracidium penetrates snail within 2 hrs. Segmentina and Hippeutis spp.
In the snail: Sporocyst Redia Daugher redia Cercaria.
Cercaria leave the snail and attaches to fresh water plants and becomes metacercaria.
Water plants include water callrop, water hyacinth, water chestnut and water bamboo.
These plants are grown in ponds and eaten raw.
Ponds are fertilized by human faeces.
When metacercaria is ingested it excysts in the duodenum and is attached to the intestinal wall.
Common in China, Vietnum, Thailand, Laos, Cambodia. Transmission is by eating fresh water plants with metacercariae. Pigs harbour infection. Incidence is highest in China. Dried plants are safer.
Attached to intestine by suckers.
Mucosa inflamed, ulcerated and abscesses form. Epigastric pain, nausia, diarrhoea.
Heavy infection leads to oedema, ascites and anarsaca.
Toxic products of worm.
Anaemia, leukocytosis, lymphocytosis, and oesinophilia.
Good prognosis if worm treated early.
1000-2000 worms affect intestinal secretions and food passage and intoxication and sensitization.
Diagnosis, Treatment, & Control
Eggs in faeces. Diffentiate from F. hapatica , Gastrodiscoides and Echinostoma sp.
Adult worms vomited or passed in stool.
Praziquantel is the drug of choice: 15 mg/kg body weight, single dose.
Sanitary disposal of human faeces.
Discourage use of night soil.
Cooking or steeping of water plants.
MORPH: Pyriform, greyish, 1.3 x 0.5 mm. Oral, Ventral and Genital suckers.
EGG: Light brown in colour, thick shell, operculated, 29 x 16 µm, Fully developed miracidium.
Adult in man Egg Miracidium Snail (Sporocyst Redia Cercaria). Cercaria enter fish and encysts as Metacercaria in fish (mullet ( Mugil cephalus ) and minnow ( Gambusia affinis ). Metacercaria swallowed in undercooked fish, excysts in small intestine and develops into adult in 7 days.
Similar to Heterophyes. Adult in jejunum of man (but also cats, dogs, pigs, and pelican). Egg ingested by snail. Miracidium in intestine of snail. Sporocyst Mother redia Daughter redia Cercaria. Metacercaria in fish. Ingested metacercaria excysts in duodenum and develops into adult in jejunum.
Far East: Japan, China, Korea, Philippines, Taiwan also Greece and Spain.
Infection is through consumption of raw fish.
Infection spread by contamination of water with human and animal excreta.
Similar to Heterophyes.
Heart and CNS granulomatous lesions may occur through eggs.