Difference between revisions of "Ascaridoidea"

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*Infection is by ingestion of the embryonated egg (egg in which a larva has formed).
 
*Infection is by ingestion of the embryonated egg (egg in which a larva has formed).
 
*Eggs can remain viable in humid environment for up to 5years.
 
*Eggs can remain viable in humid environment for up to 5years.
 +
*After hatching in the intestine, the larvae of most species (but not all) undergo hepato-tracheal migration:
 +
**egg hatches in intestine → larva penetrates intestinal mucosa → hepatic portal blood → liver → venous blood → heart → lung capillaries → alveoli → ascends trachea → swallowed → small intestine (where the adults develop).
 +
 +
 +
NOTE: there are important variations on this theme; for example, the migratory larvae of some species can cross the placenta or enter the mammary glands (examples of vertical transmission); while some species will utilise paratenic or intermediate hosts.
  
  

Revision as of 13:13, 23 December 2008



Infectious agents and parasitesWikiBugs Banner.png
PARASITES
NEMATODES



General Appearance

  • Non-bursate.
  • Big fleshy worms; typically 5-40cm long (depending on age, sex and species).
  • Three lips around the mouth.
  • A single-bulbed pharynx.


General Life-Cycle

  • Adult females in small intestine lay eggs.
  • Eggs have a thick protective shell.
  • Some also have a sticky outer albuminoid coat.
  • Eggs passed in faeces.
  • L1 → infective L2 inside the egg.
  • Infection is by ingestion of the embryonated egg (egg in which a larva has formed).
  • Eggs can remain viable in humid environment for up to 5years.
  • After hatching in the intestine, the larvae of most species (but not all) undergo hepato-tracheal migration:
    • egg hatches in intestine → larva penetrates intestinal mucosa → hepatic portal blood → liver → venous blood → heart → lung capillaries → alveoli → ascends trachea → swallowed → small intestine (where the adults develop).


NOTE: there are important variations on this theme; for example, the migratory larvae of some species can cross the placenta or enter the mammary glands (examples of vertical transmission); while some species will utilise paratenic or intermediate hosts.




Ascaridida

Occlusion of pancreatic ducts sometimes happens Pancreas - parasitic

In Peritoneal Cavity Parasitic - Pathology