Strongyloidiasis is caused by infection with Strongyloides stercoralis. Manifestations of infection can range from asymptomatic eosinophilia in the immunocompetent host to disseminated disease with septic shock in the immunocompromised host.
Strongyloidiasis is endemic in tropical and subtropical regions and occurs sporadically in temperate areas. In tropical and subtropical regions, the overall regional prevalence may exceed 25 percent. The highest rates of infection in the United States are among residents of the southeastern states [1,2] and among individuals who have been in endemic areas (including immigrants, refugees, travelers, and military personnel) [3,4]. Transmission of strongyloidiasis in a long-term care setting has also been described .
A Canadian study of newly arrived Southeast Asian refugees identified strongyloidiasis seroprevalence among Kampucheans, Laotians, and Vietnamese (76, 56, and 12 percent, respectively) . In another study, over 40 percent of Cambodian immigrants to Australia had positive or equivocal strongyloides serology indicating possible infection .
The infection begins when human skin contacts filariform larvae (the infective larval stage) of S. stercoralis, which are found in soil or other materials contaminated with human feces (figure 1) [6,7]. The filariform larvae penetrate the skin and migrate hematogenously to the lungs where they penetrate into the alveolar air sacs. The larvae then ascend the tracheobronchial tree and are swallowed.
The larvae mature into adult worms that burrow into the mucosa of the duodenum and jejunum. Adult worms may live for up to five years. The adult female produces eggs, from which noninfectious larvae (rhabditiform larvae) develop within the lumen of the gastrointestinal tract. The rhabditiform larvae are generally passed in the feces. The cycle from dermal penetration to appearance of larvae in the stool requires approximately three to four weeks.