Changes

[[Image:Toxocara canis.jpg|thumb|right|150px|''Toxocara canis'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]

[[Image:Toxocara canis.jpg|thumb|right|150px|''Toxocara canis'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]

[[Image:Toxoscaris leonina 2.jpg|thumb|right|150px|''Toxoscaris leonina'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]

[[Image:Toxoscaris leonina 2.jpg|thumb|right|150px|''Toxoscaris leonina'' - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]

*Non-bursate.

*Non-bursate

*Big fleshy worms; typically 5-40cm long (depending on age, sex and species).

*Big fleshy worms; typically 5-40cm long (depending on age, sex and species)

*Three lips around the mouth.

*Three lips around the mouth

*A single-bulbed pharynx.

*A single-bulbed pharynx

 

== General Life-Cycle ==

== General Life-Cycle ==

*Adult females in small intestine lay eggs.

*Adult females in small intestine lay eggs

*Eggs have a thick protective shell.

*Eggs have a thick protective shell

*Some also have a sticky outer albuminoid coat.

*Some also have a sticky outer albuminoid coat

*Eggs passed in faeces.

*Eggs passed in faeces

*L1 → infective L2 inside the egg.

*L1 → infective L2 inside the egg

*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 5 years

*After hatching in the intestine, the larvae of most species (but not all) undergo hepato-tracheal migration:

*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).

**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.

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.