Trematodes

• Trematodes


  Also known as "flukes"
• Trematodes


  • Flat leaf-shaped organisms
  • With oral & ventral hook or cup-shaped suckers
  • Monoecious; Hermaphrodites (possessing both male and female reproductive organs)
  • Has an incomplete alimentary canal and complex reproductive structures

  
• Trematodes have an incomplete alimentary canal (digestive system) because they have no anus
• Trematodes have complex reproductive structures because a single adult trematode has a testis, ovary, and a uterus
• Metacercaria


  Infective stage of trematodes

  
• 1st Intermediate Host (Snail)

  • Segmentina
  • Hippeutis
  • Gyraulus convexiusculus
  • Hippeutis umbilicalis
  • Cerithidea
  • Pirenella
• 2nd Intermediate Host (Aquatic Vegetation)

  • Trapa bicornis (water caltrop)
  • Eliocharis tuberosa (water chestnut)
  • Ipomea obscura (water morning glory)
  • Nymphaea lotus
• 2nd Intermediate Host (Fish)

  • BALANAK – Mugil spp.
  • TILAPIA – Tilapia spp.
  • KANDULI – Arius manilensis

  
• Heterophyid worm Definitive Host

  • Man birds
  • Fish-eating mammals
• Diagnostic Stage


  Detect characteristic eggs in feces

  
• Trematode eggs are operculated (except Schistosomes)

  
• Trematode Life Cycle


  1. Egg

  2. Miracidium – 1st larva stage

  3. Sporocyst – emerges from miracidium

  4. Rediae – intermediate larval stage

  5. Cercariae – final stage of development in snail

  6. Metacercariae – encysted form in 2nd intermediate host

  7. Adult

  
• Fasciolopsis buski (Giant Intestinal Fluke)


  • Adult measures 2.5-6.5x1.1 mm, elongated, rounded tapering ends posterior more attenuate
  • Has a horseshoe-shaped collar, bearing one or two rows of straight spines, which surrounds the dorsal & lateral sides of the oral sucker
  • Large & strong ventral sucker
  • Genital sucker (gonotyle), with spines, is adjacent to ventral sucker
  • Two oval testes situated posterior part of the body
• Echinostoma ilocanum (Garrison's fluke)


  • Egg is straw colored, ovoid

  
• Heterophyid flukes


  • Smallest trematode of man; deadliest trematode
• Trematodes are parasites of central & Southeast Asia (China, Korea, India), Northern Luzon, Leyte, Samar, Mindanao, Egypt, Middle East, Far East

  
• Trematode Eggs


  • Large, operculated, unembryonated when first passed
  • Indistinguishable from other fasciolid eggs (F. hepatica and F. gigantica)
  • Echinostoma ilocanum egg is straw colored, ovoid
  • Angiostrongylus malayanum egg is larger, golden brown, operculated

  
• Adult Trematodes


  • Has simple intestinal ceca
  • Two dendritic testes in tandem
  • Branched ovaries
  • Circumoral disk with crown of spines (49-51 spines) surrounding the oral sucker
  • Has genital sucker surrounding the genital pore

  
• Liver Fluke 1st Intermediate Host (Snail)


  • Lymnea philipinensis
  • Lymnea Auricularia rubiginosa
• Liver Fluke 2nd Intermediate Host


  • Water cress
  • Grass
  • Freshwater fish of the family Cyprinidae
• Liver Fluke Definitive/Reservoir Host

  • Sheep
  • Cattle
  • Goat
  • Man
  • Pig
  • Dog
  • Cat
  • Rat
• Liver Fluke Diagnostic Stage

  • Detect characteristic eggs in feces (eggs resemble F. buski)
  • Microscopic identification of eggs
  • Antibody detection tests

  
• Fascioliasis diagnosis


  Early invasive stages when the eggs are not yet apparent in the stool, or demonstration of characteristic eggs in feces (operculated with shoulders & small comma-shaped appendage at abopercular end)

  
• Fasciola habitat


  • Liver parenchyma, gall bladder, bilary duct
• Acute phase of fascioliasis


  Caused by the migration of the immature fluke through the hepatic parenchyma
• Chronic phase of fascioliasis

  Caused by the adult fluke within the bile ducts, with more discrete symptoms reflecting intermittent biliary obstruction & inflammation
• Ectopic locations of fascioliasis infections can occur, such as in the intestinal wall, lungs, subcutaneous tissue & pharyngeal mucosa

  
• Symptoms of fascioliasis


  • Abdominal pain
  • Hepatomegaly
  • Fever
  • Diarrhea
  • Urticaria
  • Eosinophilia
  • Vomiting
• Fascioliasis is found worldwide in areas where sheep & cattle are raised, and where humans consume raw watercress, including Europe, the Middle East & Asia
• Infections with Fasciola gigantica have been reported, more rarely, in Asia, Africa & Hawaii

  
• Fasciola eggs


  • Large, elliptical to oval, operculate, light yellowish-brown unembyronated ova
• Fasciola adult


  • Spindloid flukes measuring about 16 by 4 mm, with a cephalic cone and well-developed shoulder, larger than F. hepatica with a less-developed shoulder and shorter cephalic cone, leaf-like with transparent tegument, vitellaria found in the middle third of the body
• False fascioliasis (pseudofascioliasis) refers to the presence of eggs in the stool resulting not from an actual infection but from recent ingestion of infected livers containing eggs

  
• Diagnosis of fascioliasis


  Microscopic demonstration of eggs in the stool or in duodenal aspirate, or the adult fluke can be removed at surgery

  
• Treatment of fascioliasis


  Unlike infections with other flukes, Fasciola hepatica infections may not respond to praziquantel, so triclabendazole with bithionol is an alternative
• Paragonimus westermani is the common name for the Oriental lung fluke, which is often misdiagnosed as tuberculosis and is common in Sorsogon, Philippines
• Paragonimus westermani life cycle


  • Infective stage is human ingestion of crustacea (crabs, crawfish) infected with metacercaria, first intermediate host is a freshwater snail (Antemelania asperata or Antemelania dactylus), second intermediate host is a freshwater crayfish or crab (Sundathelphusa philippina-mountain crab), definitive host is man, wolf, fox, tiger, leopard, cat, dog, monkey

  
• Paragonimus westermani diagnosis


  Demonstrate characteristic egg in feces or sputum (may appear macroscopically in sputum as reddish-brown flecks resembling iron filings), operculated with shoulders & thick abopercular shell, "Chinese vase egg"

  
• Paragonimus westermani pathology


  • Light infections asymptomatic, high eosinophilia, chronic cough & abundant mucus in heavy infections, hemoptysis
• Paragonimus westermani is found in Japan, Korea, China, Philippines (Sorsogon), and Southeast Asia