TREMATODES

• Flukes


  • With oral and ventral suckers (acetabulum)
  • Body is covered by an integument which often bears spines, tubercles
  • No body cavity, circulatory and respiratory organ
• Types of habitat


  • Blood fluke
  • Pulmonary or lung fluke
  • Liver or hepatic fluke
  • Intestinal fluke
• Species


  • Schistosoma japonicum (Oriental Blood Fluke)
  • Schistosoma mansoni (Manson's Blood fluke)
  • Schistosoma haematobium (Vesical Blood Fluke)
  • Schistosoma intercalatum
  • Schistosoma mekongi
  • Paragonimus westermani (Oriental Lung fluke)
  • Fasciola hepatica (Sheep Liver Fluke)
  • Clonorchis sinensis (Chinese Liver Fluke, Oriental Liver Fluke)
  • Opistorchis felineus (Cat Liver Fluke)
  • Fasciolopsis buski (Busk Fluke, Giant Intestinal Fluke)
  • Echinostoma ilocanum (Garrison's Fluke)
  • Heterophyes heterophyes (Von Siebold Fluke, Dwarf Fluke)
  • Metagonimus yokogawai (Yokogawa's fluke)
• Non-hermaphroditic/ Dioecious


  Male and female worms are separate

  
• Adult blood flukes


  • Male worms are shorter & robust; females are longer & slender
  • Both male & female are provided with oral & ventral suckers
  • Males are provided with Gynecophoric canal – used by male worms to carry female during copulation
• Eggs of blood flukes

  Non-operculated
• Blood flukes require only one intermediate and one definitive host
• Infective stage of blood flukes

  Cercaria – a larva equipped with mouth, GIT & forked tail
• Diagnostic stage for blood flukes is the eggs
• Mode of transmission for blood flukes

  Skin penetration by cercaria
• Schistosomiasis/Bilharziasis is the disease caused by entry of blood fluke cercaria into human skin
• Specific habitat of adult blood flukes

  • S. japonicum - Superior mesenteric veins
  • S. mansoni - Inferior mesenteric veins or veins draining rectum
  • S. haematobium - Vesical veins or veins draining the urinary bladder
• Diagnostic specimen for blood flukes

  • S. japonicum - STOOL
  • S. mansoni - STOOL
  • S. haematobium - URINE
• Integument of adult blood flukes

  • S. japonicum - smooth
  • S. mansoni - With coarse tuberculations
  • S. haematobium - With fine tuberculations
• Number of testes in male blood flukes

  • S. japonicum - 6-8
  • S. mansoni - 8-9
  • S. haematobium - 4-5
• Number of eggs in uterus of female blood flukes

  • S. japonicum - 50-100
  • S. mansoni - 1-4
  • S. haematobium - 20-30
• Largest adult blood fluke

  S. japonicum
• Smallest adult blood fluke

  S. haematobium
• Genus of snail intermediate host

  • S. japonicum - Oncomelania quadrasi
  • S. mansoni - Biomphalaria, Planorbis and Tropicorbis
  • S. haematobium - Bulinus, Physopsis
• Characteristics of blood fluke eggs

  • S. japonicum - Non-operculated with minute lateral spine, tissue or red cells maybe adherent, size 70 – 105 x 50 -80 um
  • S. mansoni - Non-operculated egg with distinct lateral spine, measures 45-70 x 140 -180 um
  • S. haematobium - Non-operculated with distinct terminal spine, measures 112 – 170 x 40 – 70 um
• Miracidium


  Ciliated larva released from the egg when hatched
• Schistosomule


  Cercaria that has lost its tail after entry into human skin
• Sporocyst


  Sac-like larva developed from miracidium
• Redia


  Larva developed from sporocyst, absent in Schistosoma
• Cercaria


  Larva developed from redia or sporocyst, infective stage that is always fork-tailed
• Metacercaria


  Cercaria that has lost its tail after entry into a 2nd intermediate host
• Cercaria that escapes from the snail host (1st intermediate host) enters a 2nd intermediate host
• Type of 2nd intermediate host

  • Fresh Mountain Crabs
  • Snail/Mollusk
  • Fresh water vegetation, Edible Aquatic plants
  • Fishes
• 1st intermediate host genus/species

  • Paragonimus westermani - Brotia asperata
  • Fasciola hepatica - Lymnea philippinensis
  • Fasciolopsis buski - Segmentina spp., Hippeutis spp
  • Clonorchis sinensis - Alocinma spp., Bulimus spp.and Parafossarulus spp
  • Opistorchis felineus - Bithynia spp.
  • Echinostoma ilocanum - Gyraulus convexiusculus and Hippeutis umbilicalis
  • Heterophyes heterophyes - Pirenella spp. Cerithidea spp.
  • Metagonimus yokogawai - Semisulcospira spp., Thiara spp., Hua spp.
• 2nd intermediate host genus/species

  • Paragonimus westermani - Fresh Mountain crabs (Sundathelpusa spp., Parathelpusa spp.)
  • Fasciola hepatica - Watercress (Nasturtium officinale), Kangkong (Ipomea obscura)
  • Fasciolopsis buski - Water caltrop (Trapa), Water chestnut (Eliocharis), Bamboo shoots (Zizania)
  • Clonorchis sinensis - Cyprinoid Fishes
  • Opistorchis felineus - Cyprinoid Fishes
  • Echinostoma ilocanum - Kuhol (Pila luzonica) and Susong Pampang (Vivipara angularis)
  • Heterophyes heterophyes - Fishes (Mugil- balanak, Tilapia tilapia and Arius manilensis - kanduli)
  • Metagonimus yokogawai - Salmonoid Fishes (Plecoglossus and Salmo), Cyprinoid Fishes (Richardsonium)

  
• Hermaphroditic/monoecious


  Adult worms are both male and female
• Adult worms of lung, liver and intestinal flukes

  • With leaf-like, non-segmented body, still equipped with oral and ventral suckers
• Eggs of lung, liver and intestinal flukes

  Operculated
• Lung, liver and intestinal flukes are heteroxenous, requiring at least 2 intermediate hosts & 1 definitive host
• Infective stage of lung, liver and intestinal flukes

  Metacercaria
• Mode of transmission for lung, liver and intestinal flukes

  Ingestion
• Distinct features of adult worms

  • Clonorchis sinensis - Assumes a coffee bean appearance
  • Opistorchis felineus - Appears as if it has shoulders because of the CEPHALIC CONE
  • Fasciola hepatica - With branched testes, ovaries & intestina ceca
  • Fasciolopsis buski - Appears like F. hepatica but NO CEPHALIC CONE, Intestinal ceca is unbranched
  • Echinostoma ilocanum - Equipped with 3rd sucker -GENITAL SUCKER/ GONOTYL
  • Heterophyes heterophyes - Closely resembles H. heterophyes but slightly larger and with no genital sucker
  • Clonorchis sinensis & Opistorchis felineus - Closely resemble one another but: C. sinensis - with granular vitellaria & dendritic testes, O. felineus - with transverse vitellaria & lobed testes

  
• Egg morphology


  • Paragonimus westermani - Egg with FLAT operculum, opposite the operculum is an abopercular shell thickening, measures 80 – 120 um x 50-60 um
  • Clonorchis sinensis - Broadly ovoidal eggs with wide operculum, opposite the operculum is a median protuberance called abopercular knob, measures 29 x 16 um
  • Opistorchis felineus - Elongately ovoidal eggs with tapering ends, size is 30 x 11 um
  • Heterophyes heterophyes - Thick shelled light brown eggs with distinct operculum, no abopercular knob, measures 26 – 30 x 15 – 17 um
  • Metagonimus yokogawai - Thin shelled light-yellow egg, measures 27 x 16 um
  • Fasciola hepatica - Large ovoidal, yellowish brown eggs, measures 130-150 x 63-90 um
  • Fasciolopsis buski - Large operculated eggs indistinguishable from Fasciola hepatica and Fasciola gigantica, yellowish and ellipsoidal, measures 130-140 x 80-85 um
  • Echinostoma ilocanum - Straw colored, operculated ovoid eggs, measures 83-116 x 58-69 um

  
• Faust Maloney egg hatching technique and Circum-oval precipitin test are other diagnostic tests for flukes