Schistosomiasis: At-risk Populations, Symptoms, Transmission, and Treatment
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Schistosomiasis: At-risk Populations, Symptoms, Transmission, and Treatment

This article outlines a Neglected Tropical Disease that is common in Africa, Asia, and some parts of South America. Schistosomiasis is a disease caused by a parasitic worm that is transmitted through contact with contaminated water. At-risk populations, symptoms, transmission, and treatment of this disease are discussed in this article.

Throughout the world, different populations are susceptible to the contraction of specific diseases and parasites.  Schistosomiasis is categorized as a Neglected Tropical Disease (NTD) caused by a parasitic worm from the Genus Schistosoma that is transmitted by contact with contaminated water containing an intermediate host for the disease.  NTDs are becoming more of a problem, as control often needs to be tailored for specific areas and large-scale treatment can fail or has not been implemented for multiple reasons. At-risk populations, symptoms, transmission, and treatment of this disease will be discussed in this article.

At-risk populations: Large populations in developing areas with little or no sanitation are generally at risk for this type of helminth infection. 

  • Populations that contact contaminated water that also contains the intermediate host, a freshwater snail which varies along with the species of Schistosoma worm, are at-risk.
  • Species of Schistosoma worms are endemic, or naturally occurring, in Africa, Asia, and some parts of South America.  Bodies of freshwater also contain species of freshwater snails that the Schistosoma worms, known as bloodflukes, require to develop into a lifecycle stage that can infect humans.
  • People travelling to Africa, Asia, and some parts of South America should research water bodies before swimming in them, using them recreationally, or drinking from them.
  • Children in endemic areas are particularly susceptible to this disease, and often have co-infections with Malaria, HIV, and other helminth species.

Symptoms: Schistosomiasis is diagnosed by the organ system it manifests itself in and as acute or chronic infection.

  • Urinary Schistosomiasis is characterized by frequent, bloody, and painful urination after contact with contaminated water.
  • Intestinal Schistosomiasis is characterized by diarrhea, bloody feces, and abdominal pain after contact with contaminated water.
  • When Schistosoma eggs are retained in the body and build up in tissues, chronic Schistosomiasis occurs. This is characterized by inflammation of the organ due to a high number of eggs building up in one area. Schistosoma worms can also enter the bloodstream and travel to the Central Nervous System causing more complications.

Transmission: The lifecycle of the Schistosoma worms is complex, so it will be summarized here as simply as possible.  All worms within this Genus have the same lifecycle; the only thing that differs is the specific snail that serves as the intermediate host.

  • The lifecycle begins with contamination of water with human or animal feces that contain the Schistosoma eggs.
  • The eggs hatch in freshwater and infect the freshwater snail.  Inside the snail, they mature and are released back into the water in a life stage that is able to infect humans. 
  • The worms are now able to swim freely and find humans or animals.  Upon contact, the worms burrow into the skin and travel through blood and tissues to the liver.
  • Once in portal blood in the liver, they mature into adults.  The males and females pair and move to the bladder or bowel where the females lay eggs.  The eggs are then released with feces or urine and the lifecycle begins anew.

Treatment:

  • Mass Drug Administration (MDA) has traditionally been used in endemic countries.  Poor distribution in rural areas, problems with patient compliance, and local stigmas about disease and government have lead to little success with this treatment strategy.  Antiparasitic drugs such as Praziquantel are commonly used, sometimes in conjunction with corticosteroids. 
  • Some countries in Africa have adopted natural remedies, which have more of a psychological effect than a physical one. Some natural remedies used are: garlic, olive leaves, Echinacea, and curled mint.
  • Some countries focus on control of the intermediate snail hosts.  However, this can be difficult due to the multiple species of snail and ever-changing habits surrounding the bodies of fresh water. Also, the use of pesticides to control the snail poses a significant health problem for people using the water.
  • Education of susceptible populations is focused on, as some groups of people view local governments with distrust and do not understand the diseases that are endemic in their countries.

NTDs, such as Schistosomiasis, will continue to be a problem in endemic countries until local governments design specific strategies for problem areas and populations. Unfortunately, many governments in developing countries just do not have the necessary funding to deal with NTDs at the moment.

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