Parasites

Morphology

Adult female worm: 2-3 mm long & 30-40 μm in diameter, cylindrical, pointed tail, rounded anterior end
Rhabditiform (juvenile) larvae: 180-400 μm long & 15-20 μm in diameter
Filariform larvae: 500-600 μm long & 15-20 μm in diameter, notched tail
Egg: 50-60 μm x 30-40 μm; rarely seen in stool

Cytology:
Larvae may be identified in duodenal fluid, sputum, bronchoalveolar lavage, bronchial washings, and, in disseminated disease, occasionally in pleural or peritoneal fluid. Cytologic recognition relies on slender curved larvae; filariform forms show a notched tail.

Histology: 
Biopsies, especially from the duodenum/small intestine, may show adult females and larvae within crypts, glands, or mucosa/submucosa. Associated findings include eosinophil-rich lamina propria inflammation, active duodenitis/cryptitis, villous blunting or villous atrophy, and crypt hyperplasia. In severe disease, eggs, eosinophilic crypt abscesses, granulomatous inflammation, or colonic involvement may also be seen.

Differential Diagnosis:

• Schistosomiasis
• Amebiasis
• Balantidiasis
• Ancylostomiasis/Necatoriasis

Clinical notes

Mostly asymptomatic, with possible symptoms if larvae migrate to gastrointestinal (abdominal pain, diarrhoea, vomiting) or respiratory tract (dyspnea, wheeze).
Hyperinfection syndrome or disseminated strongyloidiasis in immunocompromised patients, if left untreated, can be fatal.

Ancillary Testing

Additional Information

Filariform larvae in contaminated soil can penetrate human skin and migrate via the lungs to the gastrointestinal tract, where matured adult females reproduce by parthenogenesis. Eggs hatch in the intestinal mucosa, releasing rhabditiform larvae that are either passed in stool or develop into filariform larvae causing autoinfection.