Oxyuris equi

Life cycle

Preparasitic phase

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.

Parasitic phase or_da_ar.gif (344 bytes)

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.


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Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000