Schistosomiasis is a disease caused by a type of infectious parasite. Parasites are infectious organisms that survive by living off of a host (the infected human or animal) and they are usually larger than viruses and bacteria. The parasite that causes schistosomiasis is a type of worm that invades the human body and damages several different organs.
Also known as bilharziasis, schistosomiasis isn’t found in the United States. The worms that cause it live in freshwater snails in tropical areas of South America, Africa, Asia, and Corsica, an island in the Mediterranean Sea
In these regions, schistosomiasis can devastate people’s lives. Without early treatment, it can cause a range of long-term illnesses including anemia, liver disease, brain inflammation, and lung disorders.1 Having schistosomiasis may also make females more likely to get HIV.
In this article, you'll read about how different types of schistosomiasis affect your body and how the disease can be prevented and treated.
Worldwide, schistosomiasis infects about 200 million people.2 It affects more people than any parasite other than malaria.
How Do You Get Schistosomiasis?
People can become infected with schistosomiasis by swimming or standing in water where the parasitic worms live.
A person who has schistosomiasis will excrete the worms’ eggs in their stool. In some areas, that waste is dumped into lakes or other waterways.
When the worm eggs hatch, the larvae (the worms in their early form) float freely into the water. If you’re in the water, that larvae can pass through your skin and into your body without you even noticing it.
After entering through the skin, the larvae invade the bloodstream. They mature and lay new eggs. Some of these eggs are excreted in the stool, and if the waste is dumped into a lake, it’ll infect the water. It’s a hard cycle to break in many areas that rely on this type of waste disposal.
The worms themselves don’t cause illness. The eggs are the real problem. The eggs travel to different parts of the body where they cause short-term (acute) or long-term (chronic) schistosomiasis.
Where the eggs end up in your body depends on the type of schistosomiasis that you are infected with.
Other Types of Waterborne Illnesses
Types of Schistosomiasis
There are six different species of flatworms, known as blood flukes, that cause schistosomiasis in humans.1
Schistosoma mansoni : This is the most common species, infecting over 80 million people. S. mansoni is found in areas of South America, Africa, and the Middle East. It causes severe liver damage.
Schistosoma haematobium: These worms are also found in Africa and the Middle East. Eggs infect the bladder and urinary and genital tracts.
Schistosoma japonicum: This species is located in Asia, mostly in China and the Philippines. Its eggs usually lodge in the liver and intestines. In rare cases, schistosomiasis infects the brain or spinal cord. S. japonicum is usually the cause of this type of infection, which can result in seizures and paralysis.2
Schistosoma intercalatum: The nations of Gabon, the Democratic Republic of the Congo, and Cameroon are the most common places for this species. Like other species, it can cause stomach and intestinal problems.
Schistosoma guineensis: This species is also found in west and central Africa. It becomes stuck in the blood vessels of the liver or intestine, which causes diarrhea, constipation, and bloody stool.
Schistosoma mekongi: This species is similar to S. japonicum, but it’s found along the Mekong River, especially in Cambodia and Laos. It infects the intestine and liver.
Recap
Schistosomiasis is a disease that's prevalent in regions that don’t have advanced sanitation systems. If you go into water infested with the worms, the larvae can go right through your skin and go into your bloodstream.
The larvae then lay eggs inside your body. Your immune system may overreact to these intruders, causing severe illnesses.
Symptoms
You may not have symptoms when you’re infected with the larvae that cause schistosomiasis. Many people, though, show signs of infection within weeks.3 These symptoms can last for a short time, but in some instances, people have health problems for years.
Acute
Acute, or short-term, schistosomiasis can last two to eight weeks.
Symptoms may include:
Itchiness where the larvae entered
Rash
Fever
Headache
Muscle pain
Cough or other respiratory symptoms
This type of acute condition is known as Katayama syndrome. Symptoms may start when you’re first infected or some time later.2
Chronic
Without treatment, schistosomiasis can become chronic—the symptoms can last for years and often become more serious.
Long-term problems start if parasitic eggs get permanently trapped in organs like the liver.1 Your immune system sees the eggs as something harmful, so it fights the intruders. That leads to inflammation.
Symptoms of chronic schistosomiasis include:
Stomach pain
An enlarged liver
Blood in the urine and stool
Problems passing urine
Sores or ulcers on the walls of your intestines or other internal body areas
Polyps on the liver
Cirrhosis, or scarring of the liver
Some people at high risk of repeated infections, like fishermen or people who regularly wash in infested lakes, are more likely to develop chronic schistosomiasis.
The parasitic flatworms live an average of three to ten years, but in some cases they can continue to lay eggs and infect a person for as long as 40 years.2
Complications
You can end up with serious and even permanent damage to your body when you have chronic schistosomiasis. This causes many health problems.
Cancer
When they travel to the liver, intestines, and bladder, these parasites can increase the risk of:4
Liver cancer
Colorectal cancer
Bladder cancer
Sexual Health
S. haematobium eggs may infect the uterine lining in females. This can cause lesions, which are like sores, to develop in the lining. It can cause pain and bleeding. Females are at risk of infertility and miscarriage due to these infections.1
Researchers have found that lesions in the female reproductive tract can also increase the risk of HIV infection.5
Children’s Health
In communities where schistosomiasis is common, children usually have their first infection by age 2.2 They’ll often have repeated infections throughout their childhood.
This can lead to:
Anemia
Stunted growth
Malnutrition
Learning problems
Between 60 and 80% of school-age children in areas of high rates of schistosomiasis are actively infected.1
Urinary Tract Disorders
S. haematobium may damage the bladder and kidneys.
Recap
The first possible signs that you’re infected could be skin irritation or itching. Headaches and body aches or fever are also possible.
People who visit or live in high-risk areas should be aware of the symptoms of a chronic schistosomiasis infection: stomach pains, blood in the urine, or a distended abdomen (stomach appears enlarged), which could be caused by liver problems.
Treatment
Medication can cure schistosomiasis. Biltricide (praziquantel) is an anthelmintic drug, which means it kills worm-like parasites. It’s usually taken three times in one day to treat the infection and rid the body of the eggs.
If the infection doesn’t completely clear up. another round of medication is given three to six weeks later.6
Unfortunately, treatment may not work for several reasons:
Some cases of schistosomiasis are resistant to the medication, which means the drug has no effect on the worms.
If the disease is found late, damage that’s already been done to the body can't be undone.
People who live in certain areas are very likely to be re-infected, so staying free of the parasites can be very difficult.
Prevention
Schistosomiasis can cause severe medical problems before you even know you’re infected. That’s why avoiding infection altogether is the best way to stay healthy.
If you’re visiting an area where schistosomiasis is known to be present, take these cautionary steps:2
Don’t go into freshwater. Even dipping your toes into the lake could lead to an infection.
Only drink safe water. You don’t get schistosomiasis by swallowing infected water, but the parasites can enter through your lips or other body parts that touch the water.
If you’re unsure where the water came from, boil it for at least one minute before drinking it or cooking with it.
Boil water you use for bathing (be sure to let it cool down before you use it).
If you accidentally have contact with freshwater, rub a towel vigorously on your skin to try and prevent the parasites from going through your skin.
In some regions, the World Health Organization's (WHO) strategy for schistosomiasis control focuses on reducing disease through periodic, targeted treatment with praziquantel through the large-scale treatment preventive treatment of affected populations.7
Summary
Schistosomiasis is a dangerous disease. Not everyone who gets infected ends up with serious health problems, but the risks are high.
If you travel to areas where the species are known to thrive, avoid freshwater. See a doctor if you think you’ve been exposed to parasite-infested water, even if you don’t have symptoms.
If you are diagnosed with the infection, medication usually works to get the eggs out of your system, and it's important to start treatment early before any organ damage develops.
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