ORGANISM 3 Enterobius vermicularis
GENERAL CHARACTERISTICS
COMMON NAME: Pinworm, seatworm.
GEOGRAPHICAL DISTRIBUTION: Worldwide
PATHOGENESIS: Slight eosinophilia (4 to 12 percent); secondary infections, perianai
irritations.
HABITAT: Large intestine, cecum.
INTERMEDIATE HOST: None.
RESERVOIR HOST: None known.
INFECTIVE FORM: Embryonated egg (Rhabditiform larva).
SPECIMEN SOURCE: Perianal swab or "scotch tape prep."
Figure 4-7. Life cycle of Enterobius Vermicularis.
OVA
SIZE: 25 x 55 mcm.
SHAPE: "D" shape (oval); one flattened side.
COLOR: Hyaline.
OPERCULUM: Absent.
CONTENT: First stage vermiform larva, may contain undeveloped larva known as
tadpole larva.
SHELL WALL: Triple layer.
MD0842
4-11