Strongyloides stercoralis

Abstract

Strongyloidiasis has been estimated to affect over 600 million people worldwide. It is caused by Strongyloides stercoralis , a roundworm endemic to the tropics and subtropics, especially areas where sanitation is suboptimal Autochthonous transmission has been documented in rural areas of the USA and Europe. Humans are infected when larvae penetrate the skin or are ingested. Autoinfection, in which larvae generated in the host go on to re-infect the host, leads to a state of chronic asymptomatic infection often with eosinophilia. Hyperinfection syndrome may develop when patients develop immune suppression, due to medications such as corticosteroids or following solid-organ transplantation. Hyperinfection is characterized by exponential increase in parasitic burden, leading to tissue invasion and life-threatening disease and associated bloodstream infections due to enteric organisms. Cases following use of corticosteroids for COVID-19 pneumonia have been described. Strongyloidiasis can be diagnosed by direct visualization of larvae in stool or other body fluids, or by serology. Ivermectin is highly effective in treating the disease. Patients with exposure to endemic areas and those expected to become immune suppressed should be screened and treated before starting immune suppressive agents. Empiric treatment should be considered when timely testing is not readily available.

Strongyloides stercoralis and immunosuppression in dermatology

“…Actually, hypersensitivity is an important part of the immune response to this parasite, contributing both to the pathogenesis of the disease and to its protection 16 . In fact, a primary Th2 response favors infection by increasing tissue permeability to the parasite and reducing complement activation, important for the larvae-killing capabilities of eosinophils and granulocytes 24,25 , but interleukin-13 causes increased peristalsis, possibly leading to increased larval expulsion 25 . On the other hand, HTLV-1 infection, a known risk factor for severe strongyloidiasis, results in an increased interferon-gamma production and decreased levels of interleukin-4 and IgE, which creates a favorable environment for Strongyloides stercoralis proliferation 16 .…”

“…However, immunocompetent patients with high risk of exposure should still be screened, even if without eosinophilia 5 . Moreover, in patients with risk factors for developing hyperinfection, testing should also be considered, particularly when having a history of originating or travelling to an endemic country, even if in a distant past 5,11,25 . This is especially important in patients that have immunosuppressive conditions or treatments, such as those with hematologic malignancies, undergoing transplantation or corticosteroid therapy 5 .…”

“…This is especially important in patients that have immunosuppressive conditions or treatments, such as those with hematologic malignancies, undergoing transplantation or corticosteroid therapy 5 . Indeed, in this case, both parasitological and serological assays should be used 5,25 . In some cases, pre-emptive ivermectin treatment should be considered, if a diagnostic test is not available 5 .…”

“…This broad-spectrum antiparasitic causes muscle paralysis in invertebrates by activating chlorine channels 52 . It is better tolerated and has a similar efficacy than thiabendazole, and is more effective than albendazol 5,25 . In uncomplicated infections a single 200 μg/kg/day oral dose of ivermectin for one or two days usually sufficient 5 .…”

Using newly optimized genetic tools to probe Strongyloides sensory behaviors

“…In 2017, the global prevalence of strongyloidiasis was estimated at 600 million individuals, with over three-quarters of these cases located in Southeast Asia, Africa, and the Western Pacific [2] . The prevalence of strongyloidiasis is likely underestimated, given that half of cases are asymptomatic and traditional stool-based microscopy detection methods have only limited specificity and sensitivity [3] , [4] .…”