Oxyuris equi		Contents		Rev 23-10-2025
Horse Pinworm		Classification
		Morphology and Anatomy		Life Cycle
Return to Oxyuris Menu		Distribution		Ecosystem Functions and Services
		Feeding		Management
Return to Oxyuridae Menu		Biology and Ecology		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

Classification:

Chromadorea
Chromadoria

           Rhabditida 

                       Spirurina

                          Oxyuroidea

                   Oxyuridae

 

            Oxyuris equi Schrank, 1788

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Morphology and Anatomy:

• Adults whitish in color with pointed tails

Male:

• Length 9-12 mm

Female:

• Length 100-150 mm with a long filiform tailThe elongated
• Eggs 40 x 80-90 um, slightly flattened on one side, with an operculum at one of the poles

Ref: Marchiondo, 2020

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Distribution:

Worldwide

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Feeding:

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Hosts:

Intestinal parasaite of horses, donkeys, mules and other equids. Although larval forms occur in horses of all ages, adults are mainly in young and adolescent aninaks, rrealy in mature equids.

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Life Cycle:

Direct lifecycle, no intermediate host required.

• Infective stage is an egg containing the L3 which develops in 3-7 days in the egg; the definitive host becomes infected by ingestion of the larvated egg.
• L3 larva hatches in the small intestine of the host and enters the mucosal crypts of the cecum and colon.
• In the caecum and colon, larvae develop and to the L4 in about 3-11 days after aftyer infection. A final molt of the L4 to the L5 (immature adult) occurs 45-60 days post infection, followed by a lengthy maturation phase of  about 100 days.
• After fertilization, gravid females move toward the rectum and lay their eggs around the perianal region between 139 and 159 days after infection.
• The gravid females protrude from the anus and lay 8000-60,000 eggs at one time in a sticky film directly onto the anus and perianal skin.
•  The eggs are covered by a whitish, yellowish, or greenish colored sticky fluid that adheres them to the host�s skin for several days.
• Egg masses attached to the anus and surrounding area can be irritating to the host which responds by licking and rubbing the affected area. This activity causes infected eggs or released L3 to be directly ingested by the host.
• If the egg mass becomes dried out, it can be dislodged, falling to the ground or into feed or water, thus contaminating the environment and exposing other horses to ingesting of  the infective eggs.
• Eggs can survive for 8-10 weeks. The prepatent period is 4-6 months, although egg masses can be seen on young foals as early as 3.5 months (Marchiondo, 2020).

Ecophysiological Parameters:

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Copyright  1999 by Howard Ferris.
Revised: October 23, 2025.