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610 bytes added ,  13:13, 23 December 2008
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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.
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*After hatching in the intestine, the larvae of most species (but not all) undergo hepato-tracheal migration:
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**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).
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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.
     
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