1. Strongyloides stercoralis (Threadworm)
Audra Spring

2. It’s a nematode, so it has two larval forms:
Morphology
It’s a nematode, so it has two larval forms:
Rhabditiform larvae
(non-infective form)
Filariform larvae
(pathogenic form)

3. Morphology
The size and shape of the worm are dependent on whether it’s parasitic or free-living.
Free-living females – 1 mm by 60 µm
Parasitic females – 2.2 mm by 45 µm
Eggs – 55 µm by 30 µm

4. Epidemiology Found worldwide An estimated 50 to 100 million cases
Favors warmer tropical and subtropical climates
Endemic in sub-Saharan Africa, Latin America, southeast Asia, and the southeastern United States

5. Epidemiology Worms can be free-living in the soil or live in a host.
Only females are parasitic.
The definitive host is humans, but may also affect other primates and dogs

6. Life Cycle
Dirt
Skin
Blood
Feces
Autoinfection
Intestine
Heart
Lungs

8. Strongyloidiasis
Strongyloides stercoralis has a direct parasitic life cycle, meaning it can complete its entire life cycle in the definitive host.
This causes an autoinfection in the human, because the worm keeps infecting them without ever leaving.
Disseminated strongyloidiasis, or hyperinfection, occurs in immunocomprised victims when the worms spread throughout the body, leading to sepsis and secondary bacterial infections.
Hyperinfection has an 85% fatality rate.

9. Symptoms Commonly asymptomatic But symptoms may include:
1. Gastrointestinal (diarrhea,
abdominal pain, malabsorption)
2. Respiratory (coughing, wheezing)
3. Dermatologic (ground itch, rash)
4. Anemia
People with weaker immune systems such as elderly people and children are more susceptible.
Immunosuppressed patients have further complications (disseminated strongyloidiasis and hyperinfection).
Infection is diagnosed primarily by stool samples, but string tests may also be used

10. Treatment
The drug of choice is thiabendazole, with and eradication rate of 70-90%.
Side effects, such as dizziness, drowsiness, and gastrointestinal problems
Albendazole and ivermectin are alternatives, with a 60-90% eradication rate.
These have fewer side effects than thiabendazole.
All antihelminthic drugs that either kill the worm on contact, change the permeability of their membranes, or paralyze them

11. Properly dispose of human wastes.
Prevention
Properly dispose of human wastes.
Wear Shoes.
…Don’t eat dirt.

12. References
Sing, Andreas, Lorenz Leitritz, Johannes R. Bogner, and Jürgen Heesemann,. “First-Glance Diagnosis of Strongyloides stercoralis Autoinfection by Stool Microscopy.” Journal of Clinical Microbiology. May 1999: p , Vol. 37, No October <
Lehman, Don. “Strongyloides stercoralis.” Diagnostic Parasitology University of Delaware. 1 October <
“Taxonomy, Common Name, Disease.” Strongyloides stercoralis. College of Agricultural and Environmental Sciences. 1 October <
“2-Nematodes: Hookworms (Ancylostoma duodenale, Necator americanus) & Strongyloides stercoralis.” Columbia University. 1 October <
Zepf, Bill. “Strongyloides stercoralis Infection Can Be Fatal.” American Family Physician. 15 March FindArticles.com. 1 October <
“Strongyloidiasis.” Library Identification of Parasites of Public Health Concern. 26 September Centers of Disease Control. 1 October <