Rhabditoid first-stage (L1) larvae
The first-stage rhabditoid larvae (L1) of Strongyloides stercoralis are 180-380 Ám long, with a short buccal canal, a rhabditoid esophagus and a prominent genital primordium. These L1 larvae are usually found in stool, as the eggs embryonate and hatch in the mucosa of the small intestine of the host. They may also be found in soil and cultured feces.
A: Rhabditoid larva of S.
stercoralis in an unstained wet mount of stool. Notice the
rhabditoid esophagus (blue arrow) and prominent genital primordium (red
C: Close-up of the anterior
end of a rhabditoid larva of S. stercoralis, showing the short
buccal canal (red arrow) and the rhabditoid esophagus (blue arrow).
Image taken at 1000x oil magnification.
Filariform (L3) larvae
Infective, third-stage filariform larvae (L3) of Strongyloides stercoralis are up to 600 Ám long. The tail is notched and the esophagus to intestine ratio is 1:1. Infective L3 larvae are found in soil and invade the human host by direct penetration of the skin. They may be found in respiratory specimens during cases of autoinfection.
E, F: Filariform (L3) larvae of S. stercoralis in a sputum specimen, stained with Giemsa. Notice the characteristic notched tail in Figure F. Image E taken at 200x magnification; Image F at 1000x oil magnification.
Adult parasitic females and larvae in tissue
Adults and larvae of Strongyloides stercoralis in tissue specimens, stained with hematoxylin and eosin (H&E).
G: Cross-sections of
female S. stercoralis (blue arrows) in small intestine tissue, stained
with H&E. Image taken at
I: Higher magnification
(1000x oil) of a female of S. stercoralis from the same specimen
as Figure G. Notice the intestine (red arrow)
and ovaries (blue arrows).
Cross-sections of larvae of S. stercoralis in a intestinal biopsy
specimen, stained with H&E. Image taken at 1000x oil magnification.
The patient was infected with Strongyloides following transplant of
an infected kidney.