The rhabditiform larva of a hookworm may emerge from its egg if a fecal specimen sits for several hours. This larva then may need to be distinguished from the rhabditiform or filariaform larva of Strongyloides stercoralis.
Larva
Length
Buccal Capsule
Size of Genital Primordium
rhabditiform larva of Necator or Ancylostoma
250 microns
relatively long
small and refractile
rhabditiform larva of Strongyloides
225 microns
short and blunt
large (as long as larva wide) and cellular
filariaform larva of Strongyloides
400 to 700 microns (and thin)
NA
NA
where:
• The buccal capsule is the oral opening leading to the pharynx.
• The genital primordium is in the midportion of the larva.
• The rhabditiform larva is the first stage larva.
• If still in doubt the stool can be examined for hookworm eggs. Strongyloides eggs are unusual to find except in hyperinfections.
To read more or access our algorithms and calculators, please log in or register.
