Classification and Morphology of Oesophagostomum

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Eggs and Adult Worms

Borrowed from http://cal.vet.upenn.edu/parasit/strong/strong_2b.html

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Classification

Phylum: Nematoda
Order: Strongylida
Superfamily: Strongyloidea
Family: Strongylidae
Genus: Oesophagostomum
Species: Bifurcum, Apiostomum, Colombianum, Radiatum, Dentatum, Brumpti.

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The Worm, Magnified
Borrowed from Williams and Wilkins. Parasitic Disorders: Pathology, Diagnosis, and Management. Second Edition, 1999.

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Background on the Phylum
There are over 16,000 species of nematodes (roundworms), 138 of which are well-characterized parasites of humans. The five orders that make up the phylum include Strongylida, Ascaridida, Oxyurida, Rhabditida, Spirurida, and Enoplida. Within the Strongylida order there are three superfamilies, namely Trichostrongyloidea, Strongyloidea, and Ancyclostomatoidea. Oesophagostomum are in the STRONGYLOIDEA superfamily however there is some controversy over which family they belong to. They are typically classified as either being in the Chabertidae family or in the Strongylidae family. As bursate nematodes, Oesophagostomum can potentially be classified into either family. This parasite resembles hookworms in both appearance and size. In fact, infection by Oesophagostomum cannot be distinguished from Necator americanus infection in most cases.

The classification of this parasite is useful in understanding its life cycle and clinical manifestations. As an intestinal nematode, it displays a typical life cycle and presentation of disease that is similar to other intestinal nematodes.

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Morphology

Distinct Anterior Cylindrical Morphology of Oesophagostomum bifurcum


Borrowed from http://cal.vet.upenn.edu/parasit/strong/strong_2b.html

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Because Oesophagostomum is a member of the Strongyloids, their morphology resembles that of other parasites found in this family. Adults are generally stout and white, with the male being smaller (6-16.6 mm) than the female (6.5-24 mm). The eggs are indistinguishable from hookworm eggs. They have a thin shell and range in size from 50 and 100 microns. The stage in which Oesophagostomum can be distinguished from hookworm is the L3 stage. Unlike hookworms, the Oesophagostomum males in L3 taper at the end, forming the posterior bursa. The anterior end of these parasites contains a striated cuticle located between the excretory pore and the mouth. The mouth is surrounded by oral papillae. The cylindrical buccal capsule, as depicted above, is surrounded by a protective "external leaf crown" that is called the corona radiata. Similar to other nematodes in this family, Oesophagostomum contains a well-developed, multi-nucleated digestive tract and an immature reproductive system.

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Oesophagostomum Egg



Borrowed from Leoutsakos et al. "Rectal bleeding due to Oesophagostomum brumpti. Report of a Case." Disease of the Colon and the rectum. 20:632-634.

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Introduction
Classification
Life Cycle
Epidemiology
Clinical Manifestations
Diagnosis
Treatment
Links
References