Today, the countries of the old Indochina (Vietnam, Cambodia, and Laos) still have endemic strongyloidiasis, with the typical prevalences being 10% or less.
In tropical Australia, some rural and remote Australian Aboriginal communities have very high prevalences of strongyloidiasis.
[7] In some African countries (e.g., Congo), S. fuelleborni was more common than S. stercoralis in parasite surveys from the 1970s, but the current status is unknown.
However, in some areas, another species, S. kellyi,[8] is a very common parasite of children in the New Guinea Highlands and Western Province.
[8] Knowledge of the geographic distribution of strongyloidiasis is of significance to travelers who may acquire the parasite during their stays in endemic areas.
Because strongyloidiasis could theoretically be transmittable through unsanitary bedclothes care must be taken never to use unclean hotel bed sheets in endemic areas.
The females live threaded in the epithelium of the small intestine and, by parthenogenesis, produce eggs, which yield rhabditiform larvae.
[citation needed] In the case of Strongyloides, autoinfection may explain the possibility of persistent infections for many years in persons not having been in an endemic area and of hyperinfections in immunodepressed individuals.
[13] Urocanic acid concentrations can achieve at least fivefold greater levels on the foot sole than any other part of the human body.
These autoinfective larvae penetrate the wall of the lower ileum or colon or the skin of the perianal region, enter the circulation again, travel to the lungs, and then to the small intestine, thus repeating the cycle.
Symptoms include dermatitis: swelling, itching, larva currens, and mild hemorrhage at the site where the skin has been penetrated.
If the parasite reaches the lungs, the chest may feel as if it is burning, and wheezing and coughing may result, along with pneumonia-like symptoms (Löffler's syndrome).
The intestines could eventually be invaded, leading to burning pain, tissue damage, sepsis, and ulcers.
[18] In severe cases, edema may result in obstruction of the intestinal tract, as well as loss of peristaltic contractions.
However, in immunocompromised individuals, it can cause a hyperinfective syndrome (also called disseminated strongyloidiasis) due to the reproductive capacity of the parasite inside the host.
[20][21][22] Immunosuppressive drugs, especially corticosteroids and agents used for tissue transplantation, can increase the rate of autoinfection to the point where an overwhelming number of larvae migrate through the lungs, which in many cases can prove fatal.
Larva currens appears as a red line that moves rapidly (more than 5 cm or 2 in per day), and then quickly disappears.
Locating juvenile larvae, either rhabditiform or filariform, in recent stool samples will confirm the presence of this parasite.
Ideally, prevention, by improved sanitation (proper disposal of feces), practicing good hygiene (washing of hands), etc., is used before any drug regimen is administered.
Hence, repeat treatments with ivermectin or albendazole must be administered to kill newly matured parasites that have developed from the autoinfective larvae.
This means a full treatment dose every two weeks until all larvae capable of maturing into adults have been extirpated.
Follow-up stool samples, potential additional treatment, and blood tests are necessary to ensure a cure.