The female threadworm is small (2.5 mm x 35 mm) and rarely seen in a stool specimen. Males have not been identified in parasitic phase.

The egg is rarely seen, but it is thin shelled, measures 54 x 32 mm and often is segmented.


The primary diagnostic stage in humans is the rhabditiform (hookworm) larva (see below). It is 200 to 250 mm long x 15 mm width, with a short buccal capsule, large bulb in the esophagus, and a prominent genital primordium located in its posterior half to posterior third. The filariform larva has a notched tail, is 500 mm long x 15-16mm, and has an esophageal-intestinal ratio of 1:1. The filariform larvae may be capable of existing as a free-living worm (4).

Clinical Manifestations in Humans

Symptoms of infection may range from no symptoms to abdominal pain, vomiting, and diarrhea. Cough may be present as the migrating larvae pass through the lungs. Heavy infestation of adult worms may damage the intestinal mucosa and cause malabsorption. Weight loss can occur in heavily infected people (2).

This shows a creeping Strongyloidiasis eruption on the back (6).