Microbiology
A nematode. Many animals have their own, with Strongyloides stercoralis being the main human species. S. fuelleborni in central Africa and S. kellyi in Papua New Guinea can infect humans.
Epidemiologic Risks
Walking barefoot in human stool. It is found throughout the third and developing world, including Kentucky (PubMed) and the US South.
18% of immigrants will have it; most common in those from sub-Saharan Africa (PubMed). Seroprevalence is higher than in stool studies.
10% of renal transplant patients in Houston are seropositive, high enough to warrant routine screening (PubMed).
Dogs may be a source (PubMed).
HIV likely a risk as well.
Risks in Japanese series: HTLV-1 infection, recent steroid use, organ transplant, or cirrhosis (Pubmed).
Syndromes
Local irritation/itching where you stepped, gi upset.
It is a small bowel pathogen.
With steroids or hematologic malignancy, the organism can disseminate with a hyper-infection syndrome (PubMed) from the bowel to everywhere and anywhere, often accompanied with poly-microbial bacteremia from the bowel (PubMed), hyper-eosinophilia and 2/3 will die (PubMed). They can get the thumbprint sign of the skin: the organism goes up the umbilical veins to the skin and causes a hemorrhagic rash. Larva currens due to the rapid migration of the larvae through the skin. Larva currens is a red line that moves rapidly (more than 5 cm or 2 inches a day), and then disappears.
It can cause disease both from reactivation and be acquired from the transplanted organ (PubMed).
People from endemic areas should be screened before immunosuppression, but most will not think of the disease.
And, for an off the wall cause of recurrent meningitis, chronic strongyloidiasis with human T-lymphotropic virus type 1 (PubMed).
Treatment
Ivermectin 200 micrograms /kg for 2d is probably the treatment of choice; transplant patients may require longer courses of therapy (PubMed).
And one test of cure study suggests ivermectin does not cure any patient with the standard treatment plans (PubMed) with all patients remaining PCR positive and most remaining stool positive. So how long should patients get therapy?
Thiabendazole 25 mg/kg bid for 2 days (maximum of 3 g/day). Albendazole 200 mg/kg/day for 1 to 2 days. In the hyper infection syndrome treatment for 2 to 3 weeks.
Also, 7-day course of oral albendazole 800 mg daily is INFERIOR to Ivermectin single dose (200 micrograms/kilogram body weight), or double doses, given 2 weeks apart, in Thai patients with chronic strongyloidiasis (PubMed).
Notes
There is a case of one person manifesting 75 years (seventy-five, so you know it is not a typo) after leaving an endemic area (PubMed). This is because the unusual ability to cause autoinfection: the larvae penetrate the wall of the bowel or the skin of the perineum, enters the circulation, travels to the lungs, and then back home to the small intestine. Most other parasites have to leave the human for a while to finish reproducing.
In the UK it is called threadworm.
And it makes diabetes better (PubMed).
Curious Cases
Relevant links to my Medscape blog
Last Update: 02/29/20.