Intestinal Heterophyes & Mentagrophytes

• Intestinal Flukes


  • Fasciolopsis buski
  • Echinostoma ilocanum
  • Artyfechinostomum malayanum
  • Heterophyes heterophyes
  • Metagonimus yokogawai
  • Gastrodiscoides hominis

  
• Heterophyid Flukes


  • Heterophyes heterophyes
  • Metagonimus yokogawai
• Life cycle of Heterophyes heterophyes


  1. Ova ingested by snail host

  2. Miracidium released and penetrates snail tissues

  3. Redia released

  4. Cercaria released

  5. Cercaria infects freshwater fish

  6. Metacercaria develops

  
• The life cycle of M. yokogawai is very similar to H. heterophyes
• The adult stage are found in the small intestine of the infected human host, therefore, humans are the definitive host

  
• What will be discharged in the stool is the embryonated ova
• The ova will be ingested by the snail host
• Inside the snail, the ova will release the miracidium and the miracidium will eventually penetrate the tissues of the snails forming the redia → releases the tail stage cercaria
• Cercaria infects the second intermediate host, which is a freshwater fish where they will become the metacercaria

  
• Eating raw fish will predispose human host to develop infections with these two parasites

  
• Heterophyes heterophyes


  • Intestine is simple, unbranched
  • Testes are round
  • Ovary is round
  • Vitellaria is small in quantity, found near the ovary
  • Genital sucker for attachment and release of eggs
  • Posterior to ventral sucker
• First intermediate host


  • Pirenella conica snail
  • Cerithideopsilla
• Second intermediate host


  • Bouri and Bolti (Tilapia) fishes
• Heterophyes Egg


  • Ovoid
  • Light brown in color
  • Operculated with thickened rim
  • Fully embryonated when laid – present miracidium
  • Similar to Clonorchis and Opisthorchis but posterior protruberance is absent

  
• The ova of Clonorchis and Opisthorchis have the thickened portion in the egg that is called the shoulder where the operculum is fitted onto, and they have the characteristic posterior protruberance or knob
• Pathogenesis, Pathology, Symptomatology


  • Some patients with heterophyiasis are asymptomatic
  • Worms have three suckers with spines, causing abdominal pain and mucoid diarrhea
  • Adult worms may burrow into intestinal wall and enter vascular/lymphatic system
  • Eggs and adult worms can enter vascular/lymphatic system and travel to ectopic sites like heart, brain, spinal cord
  • Heart can be affected with tissue reaction causing heart failure
  • Eggs in brain/spinal cord can cause neurological disorders and fatalities

  
• Metagonimus yokogawai has a similar life cycle to H. heterophyes, hence mode of transmission is similar
• Heterophyes heterophyes and Metagonimus yokogawai commonly inhabit the small intestine, and their life cycles and eggs are almost identical

  
• Human infection by H. heterophyes occurs in Asia, Egypt, and Hawaii while M. yokogawai is the most common intestinal fluke of humans in the Far East, Spain, and the Balkan countries

  
• Heterophyes heterophyes


  • Has a gonotyl to release eggs
  • Ventral sucker at middle portion
• Metagonimus yokogawai


  • Absent gonotyl
  • Ventral sucker releases the eggs from the uterus
  • Ventral sucker displaced laterally
• Prevention


  • Eating properly cooked fish
  • Health education
  • Proper human waste disposal