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Fun Facts!!
Carries 60-85% mortality rate for immunocomprimised patients.
Adult females may live up to 5 years and continue the reproductive cycle.
Strongyloides is the only helminth to secrete larvae (and not eggs) in feces
Unlike most parasitic worms, Strongyloides stercoralis has a heterogonic life cycle.
First described in the nineteenth century in French soldiers returning home from expeditions in IndoChina.
Taxonomy Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Rhabditida
Family: Strongyloididae
Genus: Strongyloides
Species: S. stercoralis
Morphology(parasitic vs. free-living)
Parasitic females can grow up to 2.5mm long with blunt ends and males = 0.9mm. females filariform esophagus
covers 1/3 of body length. Ovary is didelphic and opens at vulva (2/3 of bodies length)
Free living adults approx. 1 mm long. *female slightly larger than male Both sexes have rhabditiform
esophagus. Female has didelphic ovary with vulva mid way of body.
Geographic Range
Endemic Tropics and subtropics
Also can occur in temperate climates Likes warm moist climates
significance Africa, Tropical America, Pacific
Islands and parts of North America
Widespread in Eastern Europe and Mediterranean region.
*about 1% of world population is infected
Host
Definitive host: Humans, dogs,cats
Intermediate Host: None
Reservoir Host: Dog, monkey. Might use other mammals, like the two above.
Life Cycle
L3 stage penetrates skin
Enters bloodstream and migrates to pulmonary capillaries
Once in alveoli of lung, it is taken to throat where it is swallowed
Inside small intestine it matures into adult female by molting 2X
Female undergoes asexual reproduction and lay eggs that will hatch into rhabditiform.
From there they either exit the body or molt 2X more into filariform.
Filariform either penetrates intestinal wall or perianal skin, thus starting the infection all over again.
Life Cycle
Rhabditiform in the soil either develop into filariform (2X molting) or adults (4X molting).
The free-living male and female produce eggs
Eggs can either molt into infective filariform or adults
The adult worms only live through one copulation cycle in the wild. But inside humans (only females there) adults can survive longer.
Pathogenesis
Acute strongyloidiasis Wheezing Low-grade fever Epigastric tenderness
Chronic strongyloidiasis Chronic urticaria Larva currens
Severe strongyloidiasis Diffuse abdominal tenderness; abdominal distension;
hyperactive, hypoactive, or absent bowel sounds; vomiting; hematemesis; and hematochezia
Altered mental status and meningismus (if CNS involvement) Rash, Cough, respiratory distress, wheezing, hemoptysis, and
crackles Fever, chills
Symptoms
Minor infections can be asymptomatic but usually one or more of the following symptoms occur: Anemia, cough,
constipation, diarrhea, nausea, stomach ach, vomiting, weight loss
Immunosupressed and immunocomprimised patients: DEATH, distension,
shock, septicemia, neurological and pulmonary commplications
Treatment and diagnosis
stool samples will confirm the presence of this parasite. Other techniques used include direct fecal smears, culturing fecal samples on agar plates, serodiagnosis through ELISA.
Treatment includes Ivermectin is the drug of first choice for treatment because of higher tolerance in patients.
Thiabendazole and Albendazole are also sometimes used.
Control
The ideal method would be prevention by improved sanitation (proper disposal of feces), practicing good hygiene (washing of hands), etc..
Stay away from moist soil, do not work or play with contaminated water/soil.
References
http://www.dpd.cdc.gov/dpdx/html/imagelibrary/Strongyloidiasis_il.htm
http://animaldiversity.ummz.umich.edu/site/accounts/information/Strongyloides_stercoralis.html
http://emedicine.medscape.com/article/788652-overview
http://www.parasitesinhumans.org/strongyloides-stercoralis.html