Strongyloides Stercoralis, A Neglected Tropical Threadworm, Highly Prevalent In Resource-Poor Countries
The threadworm, also called Strongyloides stercoralis, is a soil-transmitted worm (helminth) endemic world-wide, yet more prevalent in hot and humid climates as well as resource poor countries with inadequate sanitary conditions. In a new report published on July 11, 2013 in PLOS Neglected Tropical Diseases, world-wide data on infection rates of threadworm have been collected from a number of sources, analyzed using spatial statistics and presented – for the first time – on a global map.
The findings document high infection prevalence rates in the general populations of high risk areas. In Thailand, for example, infection prevalence in the general population reaches almost 25%, and in Argentina tops 55%. In addition, the review highlights that threadworm is prominent in several at-risk groups such as HIV/AIDS patients and alcoholics.
Threadworms are commonly found living in soil, from where the larvae penetrate intact human skin. Through the blood circulation, heart, lung and trachea, the larvae reach the intestine where they mature to adult worms of a few millimeters in length. The “small human worm” has the unique ability of reproducing within the intestinal tract. The larvae can develop directly into adult worms in the intestine and a subsequent generation may arise. This unique feature called autoinfection may lead to life-long infections if untreated. Furthermore, the immune system plays a major role in confining threadworms to the intestine. If immune suppression occurs, e.g., by use of medicine such as corticosteroids, a threadworm infection may disseminate to any organ of the body. In such cases, patient mortality increases significantly.
The study published in PLOS Neglected Tropical Diseases documents the high prevalence rates of this worm infection and produces strong evidence that large scale interventions are urgently warranted in endemic countries. In addition, the study further highlights that migrants from resource-poor countries are at highest risk for this worm infection, likely acquiring the worm on their migratory itinerary. E.g., 70% of migrants arriving in Canada do suffer from a threadworm infection. In most cases the infection remains undiagnosed and untreated.
Finally, the study draws our attention to the fact that adequate information on prevalence is still lacking from many countries where the devastating small worm is most likely to occur. In many tropical countries of Sub-Saharan Africa, for example, no information is currently available although the prevailing socio-economic and ecological settings are favorable for the transmission of threadworms. The current information published in this review underscores that threadworm must no longer be neglected.