(Courtesy of Animal Planet)
Schistosomiasis is also known as Bilharzia, Katayama fever; Swimmer's itch; or Snail Disease.
Causative Agent: Schistosoma mansoni, S. haematobium, and S. japonicum * This disease is caused by parasitic flatworms of the genus Schistosoma that feed on the blood of humans and some animals. * Motile * Size 7-20 mm males slightly smaller. * Live in the freshwater lakes, rivers, and streams of Africa, Asia and South America.
* Infections occur when skin comes into contact with contaminated waters. * There are three main sub-species:
Schistosoma mansoni- * Most at risk are children, but any human or animal that enters the water in areas where there is inadequate sanitation, or infected snail vectors, are susceptible to infection. * Estimated 200 million people worldwide * “An estimated 85% of the world’s cases of Schistosomiasis are in Africa, where prevalence rates can exceed 50% in local populations (CDC).” * Endemic throughout southern and sub-Saharan Africa, and the Nile River of Egypt and the Sudan. South America- Venezuela, Brazil and Suriname. Also known to be found in the Caribbean but at a much lower rate.
Schistosoma haematobium- * Identical to S. mansoni areas but also includes the Maghreb region of North Africa
Schistosoma japonicum- * Found in Indonesia and parts of China and Southeast Asia
Signs and Symptoms:
Symptoms are not caused by the worms themselves but from the body’s allergic reaction to their eggs. * Most people are asymptomatic upon first infection of the flatworm. * Within days they may develop a rash or have intense itching, fever, or diarrhea. * 1-2 months may develop fever, chills, muscle ache, and cough.
Reoccurring infections with the Schistosoma cause more severe symptoms * Anemia, malnutrition, and learning difficulties in children. * After years of infection, the parasite can damage the liver, intestine, spleen, lungs, and bladder. * If left untreated, Schistosoma will persist and cause chronic symptoms which include abdominal pain, enlarged liver, blood in the stool or blood in the urine, problems passing urine, and increased risk of bladder cancer (CDC). “Chronic effects are usually severe and are caused by fibrous degeneration of tissue around deposited eggs of the parasite in the liver, lungs, and central nervous system (FDA).”
Snails are the first intermediate hosts where they go through a developmental stage, and then re-enter the water where they seek out their next host with a blood supply. (Oberholzer) (Drugline) The life cycle of Schistosoma mansoni: 1. Eggs are eliminated in urine or feces.
2. Eggs hatch.
3. Penetrate snail and go through developmental stages
4. Release from snail and penetrate human host.
5. Migrate thru tissues to residence (Trematodes)
Infection occurs when skin comes into contact with larval cercariae in freshwater lakes and rivers. The larvae are attracted to the fatty acids in the skin. They swim toward their new host and enter through a hair follicle and excrete a chemical that dissolves the skin allowing entry into the host. Once inside they mature into adult worms where they live in the blood vessels close to the liver, near the large and small intestines, and in the bladder and the ureters. They mate in the blood stream and deposit their eggs near the intestines where some of them will be excreted in the feces or urine which will start the cycle all over again.
Treatment includes Praziquantel, a broad spectrum…