PARASITES AND PARASITIC
DISEASES OF DOMESTIC ANIMALS
Oxyuris equi has a direct life cycle and its predilection site is the
large intestine (B). After
fertilization, the gravid female migrates to the anus of the definitive host, emerges head
first and lays her eggs in clumps (C)
in a yellowish-grey gelatinous material on the perineal skin. After completing their egg
laying, the females pass outof the anus and die.
Development to the infective third stage larva takes place inside the egg and is
quite rapid, taking only 3 to 5 days.
The infective stage of Oxyuris equi is an egg containing a third stage
larva (Egg + L3) and the definitive host is infected by ingestion.
Larvae (L3s) hatch in the small intestine (A),
pass into the large intestine and enter the mucosal crypts of the cecum and colon.
Here they molt to the fourth stage (L4) about 8 to 10 days after infection. The final molt
to immature adults takes place between 45 and 60 days after infection and this is followed
by a lengthy maturation phase of about 100 days until gravid females lay their eggs
anywhere from 139 to 156 days after infection.
The prepatent period is approximately 5 months.