What are the other Names for this Condition? (Also known as/Synonyms)

• Bilharziasis
• Schistosome Infection
• Snail Fever

What is Schistosomiasis? (Definition/Background Information)

• Schistosomiasis is a parasitic infection caused by a type of flatworms (soft-bodied invertebrates) called schistosomes. These waterborne worms infect mammalian hosts including humans, by penetrating the skin in (contaminated) freshwater bodies
• Schistosomiasis is common in the tropical areas, specifically in certain regions of Central and Southern Africa. But, the infection is also reported from Southeast Asia and South America
• The known risk factors for the infection include traveling to or residing in a country where Schistosomiasis is prevalent, poor waste disposal and water treatment, and the use of contaminated water for day-to-day life (especially seen in the local and native communities)
• In some cases, those infected may show no symptoms or have lasting clinical complications. However, inflammation, intense pain, and potential organ damage are a few of the symptoms and complications that can occur in individuals with severe Schistosomiasis
• Schistosomiasis can be diagnosed via a blood serum test and anti-parasitic drugs may be prescribed, if it is suspected/confirmed. In some regions when a majority of the population is affected, large-scale community treatments are undertaken
• With treatment, Schistosomiasis is known to resolve over a period. If the infection is left untreated and it becomes chronic, damage to vital organs (liver and kidney), paralysis, and deaths have been reported

Who gets Schistosomiasis? (Age and Sex Distribution)

• Schistosomiasis is prevalent in the tropical regions of Central and Southern Africa, Southeast Asia, and South America
• All races, ethnicities, and both male and female genders are susceptible to infection
• Children become infected at higher rates, most likely because they spend more time in or around contaminated waters
• Of all the regions of the world, the infection is highly-endemic to Central Africa. Tens of millions of people are suspected to be affected each year, with approximately 85% of them being Africans

In some countries, loss of life and economic impact caused by Schistosomiasis is second only to malaria.

What are the Risk Factors of Schistosomiasis? (Predisposing Factors)

The risk factors of Schistosomiasis include the following:

• Residing in or traveling to an area where the infection is endemic
• Conducting domestic, recreational, occupational, or agricultural activities in and around contaminated waterbodies such as ponds, lakes, and streams
• Having poor waste disposal and water treatment facilities
• Schistosomes can also infect other warm-blooded animals, such as pets and livestock. Such infected animals frequently facilitate the spread of infection to different areas

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Schistosomiasis? (Etiology)

Schistosomiasis is caused by a parasitic waterborne flatworm that enters a human host by penetrating the skin.

• Once through the skin, the parasite generally enters the bloodstream of the host, where it matures and reproduces
• Eggs are eventually released into the bloodstream, which are expelled through urination and defecation, or become embedded in body tissue, causing symptoms and complications
• Urination or defecation into water can lead to a repeated parasitic life cycle as eggs are expelled into the environment
• Freshwater snails act as the secondary hosts for the parasite and are part of the life cycle of the parasite

There are 5 different parasitic strains of Schistosomiasis that can cause infection in humans:

• Schistosoma mansoni, found throughout Africa and South America
• Schistosoma haematobium, found throughout Africa
• Schistosoma japonicum, found in Indonesia, parts of China, and Southeast Asia
• Schistosoma mekongi, found in Cambodia and Laos
• Schistosoma intercalatum, found in Central and West Africa

What are the Signs and Symptoms of Schistosomiasis?

The signs and symptoms of Schistosomiasis depend on where the eggs of the worm localize in the body. If the parasitic eggs are excreted through urine or feces, the infection may resolve with no symptoms. However, if the parasitic eggs become embedded in body tissue, they may lead to a variety of symptoms such as the following:

• Rash and/or itchy skin at location of initial infection
• Fever
• Cough
• Muscle aches
• Abdominal pain
• Diarrhea
• Bloody stool and/or urine

Following initial penetration of the flatworm, itching, skin rash, and bleeding may develop within 2 days. Severe symptoms, such as muscle aches, abdomen pain, diarrhea, bloody stool/urine, and fever generally develop 1-2 months after the initial infection.

It is important to note that the presence of a sign or symptom does not indicate an infection. Furthermore, in some cases, infection may be experienced without the appearance of any symptoms too.

How is Schistosomiasis Diagnosed?

Schistosomiasis is diagnosed on the basis of the following tests and exams:

• A physical examination and assessment of symptoms, if any
• An evaluation of the affected individual’s place of residence, recent travel history and outdoor activity, and medical history
• Checking for the presence of eggs in stool or urine sample can confirm infection
  • Schistosoma mansoni and S. japonicum can be identified through stool samples
  • Schistosoma haematobium can be identified through urine samples
  • Of the 5 types of Schistosomiasis, these 3 (above) are the most common to infect humans
• Serum test to check for the presence of antibodies: The serum test is only accurate when an individual has not been in contaminated water for the last 6 weeks. The result of the serum test should be interpreted carefully, due to the fact that a positive test may occur in individuals, after drinking contaminated water without resulting in active clinical infection

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Schistosomiasis?

The possible complications of Schistosomiasis, particularly of the condition is left untreated and it becomes chronic, include:

• Anemia (decreased number of red blood cells) and malnutrition
• Seizures and paralysis (loss of ability to move)
• Urinary tract obstruction by the parasites can result in frequent urinary tract infections (UTIs)
• Urinary bladder cancer: The type of cancer is usually a squamous cell carcinoma of urinary bladder, caused by long-term irritation of the bladder lining by the parasitic infection
• Liver damage and kidney failure

How is Schistosomiasis Treated?

• The main treatment for Schistosomiasis is prescription anti-parasitic medications
• Treatments on a mass scale may be undertaken, if many individuals in the community report blood in urine
  • Generally, in villages, where more than 50% of the inhabitants are infected, every individual in the village is treated for infection
  • If in between 20% and 50% of the inhabitants are infected, all children are treated

How can Schistosomiasis be Prevented?

The following are some guidelines for the prevention of Schistosomiasis:

• Establishing water and wastewater sanitation, to prevent schistosome eggs from entering fresh water from human waste
• Exterminate freshwater snails that act as the secondary hosts for the parasite. Without freshwater snails in the environment, the parasite cannot develop and infection of humans cannot occur, since they are part of the life cycle of the parasite
• Avoid water-related activities in areas of known parasitic infestation
• Boil or filter water before using it for drinking and cooking purposes. The parasite can enter the bloodstream through the mouth, throat, or esophagus after consuming contaminated water

Conducting activities in the ocean or swimming in chlorinated pools does not present a risk for being infected with Schistosomiasis.

What is the Prognosis of Schistosomiasis? (Outcomes/Resolutions)

• Following treatment with an anti-parasitic drug, the infection and accompanying symptoms typically resolve rapidly
• Without treatment, Schistosomiasis can lead to a variety of severe symptoms and complications. Mortality is a possibility with prolonged and severe cases of infection

Additional and Relevant Useful Information for Schistosomiasis:

• Schistosomiasis is very rare in the United States; however, cases of infections have been recorded in individuals who travel and return from endemic areas
• Schistosomes can survive without a host only for 48 hours, following which the parasite is known to starve and die
• Affected hosts normally do not feel or notice the parasite penetrating the skin during initial infection
• Ongoing research and development is underway to produce Schistosomiasis vaccine