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Ascariasis
[Ascaris lumbricoides]

Fertilized and unfertilized Ascaris lumbricoides eggs are passed in the stool of the infected host.  Fertilized eggs are are rounded and have a thick shell with an external mammillated layer that is often stained brown by bile.  In some cases, the outer layer is absent (known as decorticated eggs).  Fertile eggs range from 45 to 75 m in length.  Unfertilized eggs are elongated and larger than fertile eggs (up to 90 m in length).  Their shell is thinner and their mammillated layer is more variable, either with large protuberances or practically none.  Unfertile eggs contain mainly a mass of refractile granules.

Ascaris lumbricoides fertile egg Ascaris lumbricoides fertile egg
A B

A, B: Fertilized eggs of A. lumbricoides in unstained wet mounts of stool, with embryos in the early stage of development.

Ascaris lumbricoides fertile egg Ascaris lumbricoides fertile egg
C D

C: Fertilized egg of A. lumbricoides in an unstained wet mount of stool, undergoing early stages of cleavage.  Image taken at 200 magnification.
D: Fertilized egg of A. lumbricoides in an unstained wet mount of stool.

Ascaris lumbricoides fertile egg Ascaris lumbricoides fertile egg
E F

E: Fertilized egg of A. lumbricoides in an unstained wet mount of stool, 200 magnification.  A larva is visible in the egg.
F: Fertilized egg of A. lumbricoides in an unstained wet mount of stool.

 

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