Strongyloides stercoralis and Strongyloidosis

Strongyloidosis is a chronic, soil-transmitted, intestinal parasitic disease. Strongyloides stercoralis is a roundworm and the main causative agent of this disease. S. stercoralis has a unique life cycle, which consists of direct (homogonic) development and indirect (heterogonic) development. Parasitic adult females produce both sexes of the next generation parthenogenetically. Female larvae can choose the direct or indirect development depending on various environmental conditions. Autoinfection is one of the characteristic features of this parasite, which causes hyperinfection and disseminated infection. Strongyloidosis occurs mostly in humid tropics and subtropics of more than 70 countries, affecting people between 30 million and 100 million or higher. However, the precise number is not known up to the present, because of difficulties in diagnosis. Even in highly developed countries, like the USA, serious problems have been caused by transmission of S. stercoralis through organ transplantation. We describe the current status of strongyloidosis with special reference to biology, epidemiology, immunology, and vaccine development.