Microscopy:

Eggs

Eggs of Oesophagostomum bifurcum, the most-common species infecting humans, cannot be differentiated morphologically from the eggs of Necator or Ancylostoma (eggs of other animal oesophagostome species tend to be larger than typical hookworm eggs, however).  The eggs of O. bifurcum measure 60-75 µm long by 35-40 µm wide.  Eggs are often in a later stage of cleavage than hookworm species when shed in feces.

A	B

A, B: Eggs of Oesophagostomum sp. in an unstained wet mount of stool.

Adults

Adults of Oesophagostomum spp. are bursate nematodes, related to and morphologically-similar to, the hookworms.  Females measure 1.5-3.0 cm in length; males are smaller.  In both sexes, the anterior end has a cephalic inflation or vesicle, a transverse cephalic groove, and an oral opening guarded by external and internal leaf crowns (corona radiata).  The cuticle is ringed with transverse striations.  The posterior end of the female is short and pointed; the male possesses a symmetrical bursa and paired, equal spicules.  Adults reside in the large intestine of the definitive host.

C	D

C: Adult of Oesophagostomum sp.
D: Higher magnification of the anterior end of the specimen in Figure C.  Note the presence of the cephalic vesicle (CV), cephalic groove (CG) and esophagus (ES).

E	F

E: Higher magnification of the anterior end of the specimen in Figures C and D.  Note the presence of the cephalic vesicle (CV) and corona radiata (CR).
F: Posterior end of a female Oesophagostomum sp., showing the pointed tail.

G	H

G, H: Posterior end of a male Oesophagostomum sp., shown in two different focal planes.  Note the spicule (SP) and bursa (BU).

 

I	J

I, J: Cross-sections of an adult of Oesophagostomum sp. in a colon biopsy specimen from a patient from Africa, stained with hematoxylin and eosin (H&E).  Note the large, platymyarian muscle cells (MU), intestine with brush border (IN), paired reproductive tubes (RT), and thick, muscled esophagus (ES).  Images taken at 200x magnification.