medical parasitology

1. Strongyloides
stercoralis

2. Synonym Strongyloides instestinalis
Anguillula stercoralis
Common Name Threadworm
Disease Strongyloidiasis
Cochin-China Disease
Geographic Distribution Cosmopolitan (lower incidence
compared to hookworm) and
Sporadic in temperate and cold
regions which parallels
Hookworm
Principal Host Man
Incubation Period in Man 28 days
Mode of Infection Contact with the intact skin of
human beings with the
filariform larva; walking
barefoot

3. FEMALE
ParasiticFemale
 2.2 mm
 Colorless, semitransparent
 Filariform nematode fine
striated cuticle
 Slender tapering anterior
end, and short conical
posterior end
 Vulva 1/3 of body length
from posterior end
 Uteri contain 8-12 thin
shelled, transparent,
segmented ova
Free- Living Female
 1mm, smaller than parasitic
 Resembles typical rhabditoid
free-living nematode
 Muscular esophageal
pharynx is double-bulbed
and intestine is straight
 Vulva 2/5 length from
posterior
 Uteri contain a single column
of thin-shelled, transparent,
segmented ova

5. MALE
ParasiticMale
 Rhabditoid in type
 Identical with free living
male except slightly larger
buccal chamber
Free- Living Male
 0.7mm long
 Tail is curved ventrad
 2 equal copulatory spicules
and gubernaculums
 No caudal end ( a protective
wing-like structure)

6. LARVAE
Rhabditoid Larvae
 Feeding stage of the parasite
 Open mouth, short, and stout
 Club-shaped anterior portion
with a post median
constriction and a posterior
bulbous esophagus
 Relatively conspicuous
primordium on the ventral
side halfway down the midgut
 Buccal cavity is short and of
small diameter
 Molt 4 times before becoming
an adult
Filariform Larvae
 Non-feeding stage
 Close mouth, long, delicate,
and slender
 Has long esophagus
 Tail with notched or blunt or
fork appearance
 Infective to man
 Can swim in water, and
survive in water or soil for
several threads

10. Egg or Ova  Ovoid
 Thin shelled
 Transparent
 Partially embryonated
 Hatch in mucosal epithelium
 Strongyloides stercoralis is an ovoviviparous

11. Mode of Infection
▶ Penetration on bare skin
Disease
▶ Strongyloidiasis, Cochin China diarrhea

12. Clinical Manifestations
▶ Dermatitis, swelling, itching, larva currens and
mild hemorrhage at the site where the skin has
been penetrated
▶ Pnuemonia-like symptoms Lofflers
syndrome
▶ Tissue damage, sempsis and ulcers
▶ Hyperinfection syndrome has a mortality rate of
close to 90%

13. LIFE CYCLE

15. Specimen
▶Feces
▶Sputum
▶Duodenal aspirates
▶Gastric aspirates

16. Diagnostic Stages:
▶ S. sterocoralis eggs = Papanicolau stained
smears of duodenal or gastric aspirate
▶ Filariform Larvae = Ascitic Fluid, CSF,
Feces and Sputum
▶ Rhabditiod Larvae = Stools, duodenal
aspirates and sputum

17. Immunologic Test
▶ Indirect hemagglutination
▶ Enzyme-linked immunosorbent assay (ELIZA)
Treatment
▶ Ivermectin with albendazole (uncomplicated strongyloidiasis)
▶ Ideal method would be prevention by improved sanitation (proper
disposal of feces)
▶ Practice good hygiene (washing of hand is the right manner)