Classification and Morphology of
Eggs and Adult Worms
Apiostomum, Colombianum, Radiatum, Dentatum, Brumpti.
The Worm, Magnified
Borrowed from Williams and Wilkins.
Parasitic Disorders: Pathology, Diagnosis,
and Management. Second Edition, 1999.
Background on the
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,
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
cycle and clinical manifestations. As an intestinal nematode, it displays
a typical life cycle and presentation of disease that is similar to other
Distinct Anterior Cylindrical Morphology of
Borrowed from http://cal.vet.upenn.edu/parasit/strong/strong_2b.html
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.
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.