Oesophagostomum bifurcum

The definitive hosts of Oesophagostomum spp. become infected from the ingestion of infective L3 larvae, which develop in the environment. L3 larvae are longer than the L3 larvae of hookworms, measuring 710-950 µm in length. The intestine is made-up of alternating triangular-shaped cells (zigzag gut cells). The tail end has a long, thin, tapered sheath, with a considerable gap between the end of the tail and the end of the sheath.

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.

(From DCD-DPDx 2013)

Oesophagostomum spp. are primarily parasites of livestock and non-human primates, and humans tend to be only incidental hosts for parasites in this genus. Eggs of O. 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.

From CDC-DPDx