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Strongyloides stercoralis: ultrastructural study of newly hatched larvae within human duodenal mucosa
  1. Daniele Dionisio1,
  2. Lidia Ibba Manneschi2,
  3. Simonetta di Lollo3,
  4. Alessandra Orsi4,
  5. Alessia Tani2,
  6. Alessandra Papucci3,
  7. Francesco Esperti1,
  8. Francesco Leoncini5
  1. 1Infectious Diseases Unit, Pistoia Hospital, Piazza Giovanni XXIII, 51100 Pistoia, Italy
  2. 2Department of Human Anatomy and Histology, University of Florence, Florence, Italy
  3. 3Institute of Pathology, University of Florence
  4. 4Laboratory for Microbiology and Virology, Careggi Hospital, Florence, Italy
  5. 5Infectious Diseases Unit, Careggi Hospital
  1. Dr Dionisio email: infdispt{at}


Aim—To investigate the ultrastructural features of the newly hatched larvae of Strongyloides stercoralis in human duodenal mucosa.

Methods—Duodenal biopsies from an AIDS patient were studied by transmission electron microscopy to investigate morphology, location, and host–worm relations of newly hatched larvae.

Results—Newly hatched larvae were found in the Lieberkuhn crypts within the tunnels formed by migration of parthenogenic females. Delimiting enterocytes were compressed. Release of larvae into the gut lumen was also documented. It was shown that both a thin and a thick membrane surrounded the eggs and larvae, as a tegument derived respectively from parasite and host. Segmentary spike-like waves, caused by contractures of worm body musculature, were observed on the surface of newly hatched larvae, and their intestinal lumen was closed and empty, with no budding microvilli. Immaturity of the cuticle and some degree immaturity of amphidial neurones were found, but there was no evidence of either immaturity or signs of damage to other structures.

Conclusions—Newly hatched larvae of S stercoralis appear to be a non-feeding immature stage capable of active movement through the epithelium, causing mechanical damage. The tegument resulting from the thin and the thick membrane may protect the parasite and reduce any disadvantage caused by immaturity.

  • Strongyloides stercoralis
  • ultrastructure
  • larvae
  • immune deficiency

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