Digestive Trematodes


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Digestive Trematodes

  1. 1. Digestive Tract Trematodes FAMILY ECHINOSTOMATIDAE - intestinal parasites recognized by their anterior collar of spines.   Echinostoma - Chap. 17 Cosmopolitan parasite of ________________________________ – shows low host specificity Common definitive hosts in Wisconsin are ___________________________________________________ Human cases have been reported in the Orient, primarily Taiwan and Indonesia – _________species reported from humans Taxonomy a mess – _____________described species. E. revolutum now confined to bird hosts; E. trivolvus is new name for species in mammals in Wisconsin.
  2. 2. Morphology of Adult Echinostoma Adults are elongate, up to an inch in length. Characteristic structure is: ____________________________________________ ______________________ Internal organs are distinct and easy to identify.
  3. 3. Morphology of Adult Echinostoma Vitellaria Testes Mehlis’ gland Ovary uterus Collar of spines around oral sucker
  4. 4. Life Cycle of Echinostoma Parasite shows low host specificity throughout cycle   1. Adults occur in _________ ________________________________________   2. Eggs are released via the feces into an aquatic habitat.   3. Miracidia hatch, swim to snail, and penetrate ________________________ (1 st intermediate host).
  5. 5. Life Cycle of Echinostoma 4. Sporocysts and rediae occur within snail. Cercariae are released. 5. Cercariae penetrate ________________________________________________ (2 nd intermediate hosts) and encyst as metacercariae.   6. Definitive host is infected by ingesting 2nd intermediate host, metacercariae excyst in stomach, and adults mature in small intestine.  
  6. 7. Echinostoma How are humans infected? ______________________________ ____________________________________________________   <ul><li>PATHOLOGY - inflammation of the small intestinal mucosa at the attachment site. </li></ul><ul><ul><li>  Symptoms are intestinal pain and diarrhea. </li></ul></ul><ul><ul><li>  Parasite is never life-threatening. </li></ul></ul>
  7. 8. FAMILY HETEROPHYIDAE - family of tiny flukes in the small intestine of fish-eating birds And mammals. Two heterophyids are important human parasites.   Heterophyes heterophyes – Chap. 18, p. 291-292 Adults are small parasites in the human small intestine. Distributed in the Orient (Japan, Korea, China, Taiwan, and the Philippines), Africa, and Asia Minor. Reservoir hosts - ______________________________________ Parasite is a __________________________  
  8. 9. Morphology of Adult Heterophyes Adults are small, less than 2 mm in length. Characteristic structure is the ____________________ , a muscular and spinous sucker surrounding the common genital pore. Gonotyl is located near acetabulum. Ovary is anterior to testes. Testes are opposite and posterior.  
  9. 10. Life Cycle of Heterophyes 1. Adults occur __________________________________________________________________ 2. Eggs are released in feces and must be eaten by aquatic ____________________ (1 st intermediate) 3. Miracidia hatch in snail and undergo sporocyst and redial generations.
  10. 11. 4. Free-swimming cercariae are released from snail and penetrate a _____________________________ (2 nd intermediate) where metacercariae encyst in the muscle. 5. Humans become infected ______________________________________________________________. Adults mature in small intestine in 7-10 days.
  11. 12. Life Cycle of Heterophyes Mullet second intermediate host Metacercaria in mullet muscle
  12. 14. Pathology of Heterophyes <ul><li>ADULTS: ________________________________________ _________________________________________________ _________________________________________________ </li></ul><ul><li>In heavy infections, the mucosa and submucosa may become ulcerated. </li></ul><ul><li>EGGS can get into the bloodstream and may be carried to the _____________________ where they cause a severe tissue reaction called ____________________________________ . </li></ul><ul><ul><li>  14% of fatal heart attacks in the Philippines </li></ul></ul>
  13. 15. Heterophyes DIAGNOSIS - Identify eggs in the feces. Eggs are similar to Clonorchis. (We do not have slides of Heterophyes eggs.)   TREATMENT -
  14. 16. Metagonimus yokagawai Common heterophyid trematode in humans in the Orient (overlaps with Heterophyes ), Russia, and the Balkan countries. ADULT MORPHOLOGY - small, less that 2 mm long Acetabulum ____________________________________________________ There is no gonotyl. Seminal vesicle and seminal receptacle are ___________. acetabulum
  15. 17. Metagonimus LIFE CYCLE, PATHOLOGY, DIAGNOSIS, AND TREATMENT is identical to that of Heterophyes.
  16. 18. STRIGEOID TREMATODES - 2 families of trematodes that inhabit the small intestine of birds and mammals - Chapter 16, p. 247-249   Alaria spp.   Many species of Alaria occur in the small intestine of carnivores. Alaria canis in dogs. Alaria americana in foxes. Alaria mustelae in mink and weasels. Alaria taxideae in badgers (we will examine this one in lab)  
  17. 19. Morphology of Adult Alaria Body is divided into 2 regions: 1. 2. Three suckers are present - _____________________________________________________________________   Common genital pore is posterior.
  18. 20. Life Cycle of Alaria LIFE CYCLE is unusual in that 3 or 4 hosts may be involved.   1. Adults in small intestine of carnivore definitive host.   2. Eggs in feces hatch in water releasing miracidia that penetrate _____________________ first intermediate host.   3. Cercariae released from snail penetrate a _____________________ second intermediate host and transform into an unencysted stage called the ______________________ .
  19. 21. Life Cycle of Alaria 4. If tadpole is eaten, frogs, snakes, mice can serve as _____________________________________________. Mesocercariae undergo no further development.   5. Carnivore becomes infected by eating tadpole or paratenic host.
  20. 22. Life Cycle of Alaria 6. ______________________ penetrate the intestine, burrow through the diaphragm, and reach the lungs. Here they become _______________________ 7. Metacercariae migrate up the respiratory tree and are swallowed. Adults in the carnivore's ______________________  
  21. 23. Pathology of Alaria infections PATHOLOGY - Adult parasites cause severe damage to the small intestine of the carnivore. Often occur together in clumps.     Forebody Hindbody
  22. 24. Pathology of Alaria infections <ul><li>HUMAN INFECTION – few cases involved infection with _______________________________ </li></ul><ul><ul><li>most cases involved mesocercariae migrating to the eye </li></ul></ul><ul><ul><li>one fatal case occurred in Canada from ingestion of poorly cooked _____________________________ </li></ul></ul><ul><li>Mesocercariae were identified in nearly every organ at autopsy. </li></ul><ul><li>Photo shows mesocercaria in lung </li></ul><ul><li>  </li></ul>
  23. 25. Uvulifer ambloplitis is associated with ____________________________ Fish are the 2 nd intermediate host – common in ____________________________ ____________________________
  24. 26. Uvulifer Adults occur in the ________________________________________________ (fish-eating birds). This is the only definitive host – shows ____________________________________
  25. 27. Uvulifer Blackspot is caused by the _____________________________ in the fish muscle and fins. ___________________________ is produced by the fish in response to the parasite and is deposited into the metacercarial cyst.
  26. 28. Uvulifer LIFE CYCLE involves: (1) _______________________________ (2) ____________________________________ (3) ___________________________ (only one - shows high host specificity)
  27. 29. Uvulifer What happens if humans eat poorly cooked fish with blackspot?