Strongyloides stercoralis: Hyperinfection Syndrome and Disseminated Disease

Abstract

Threadworm (Strongyloides stercoralis) is the nematode helminth which causes strongyloidiasis in every continent of the world, especially tropical and subtropical areas, and infects more than 100 million people. The symptoms are dependent on the patient condition, from uncomplicated to highly severe and finally lead to mortality.  The severe infection can be distinguished into two patterns, hyperinfection syndrome (an amplification of normal parasite life cycle in the usual pattern) and disseminated strongyloidiasis (a massive migration of parasite larva into the organs that are not involved in normal life cycle), according to the site of pathology. Even if the infection shows mostly mild symptoms, the patient will develop more severe symptoms when immunocompromised, such as having immunosuppressive agents, malignancy, or some viral infections. The conventional laboratory diagnosis remains another limitation because of many factors. Direct wet smear, the standard detection method, has low sensitivity in detecting the parasite larvae in stool samples. Other methods such as agar plate culture, despite having higher sensitivity, are still routinely unusable because of time consumption.  The detection of parasite larva in sputum is ultimately limited to severe cases only. The treatment is another concerning issue; ivermectin and azoles show inconsistent cure rates depending on many factors and also several adverse effects which need to be considered. So, the most appropriate way to avoid severe infection is to protect oneself from the parasite.