Schistosomiasis (Bilharzia) Prevention

Photographed by Krish Maharaul

Malawians will tell you that you haven’t really visited Malawi until you have seen Lake Malawi.  This lake is an incredible tourist attraction and Malawi’s pride!  (Thank you to my patients and their friends who have shared their Lake Malawi pictures with me so we can all enjoy them!) For Malawian residents, the Lake is where we go to relax and have family vacations.  Family getaways are so important for maintaining healthy family relationships that help children thrive.  For that reason, I don’t want to tell you not to go to Lake Malawi. However, Lake Malawi is home to schistosomiasis, so we need to take precautions to reduce the risk of exposure as much as possible. Schistosomiasis is also found in fresh water in most of Africa and other parts of the world.

What is schistosomiasis and how is it spread?

Photographs by ‘BAKE’N’FLAKE

Schistosomiasis (also called bilharzia) is an infection caused by a parasite, more specifically a worm.  The eggs are released into fresh bodies of water when someone that has schistosomiasis pees or poos in or near the water.  Once in the water, the eggs hatch and the larvae (immature form of the worms) are absorbed by a type of freshwater snail. Inside the snail, the larvae continue to grow and develop into a second stage of larvae. These parasites eventually leave the snail and go into the water where they will survive for another 48 hours. The parasite is absorbed from the water into the human body through the skin.

What happens in the body?

The parasites that are released in the water from freshwater snails dig into human skin and travel in the blood, usually to the liver and bowel.  After several weeks the larvae grow into adult worms and release eggs into the bowels and bladder, starting the cycle all over again.  The parasite can remain in the body for several years releasing eggs that could cause chronic problems with the bowels, bladder, liver, heart, lungs, and the nervous system. 

What are the signs and symptoms?

When exposed: Some people get itchy red bumps where the tiny worms dug into the skin, but most people don’t have any symptoms when exposed.  

After about a month after exposure:  Some experience a reaction to the worms being released causing high fever, rash (itchy, raised, blotchy), cough, diarrhea, and muscle aches. This is called acute schistosomiasis. If untreated, these symptoms will go away after a few weeks. 

Months and years later: The long-term effects of schistosomiasis depend on where the eggs have lodged and caused scarring.  Symptoms range from blood in the urine or stool, anemia, abdominal pain, cough, heart problems, seizures, or headaches. 

Ideally children under the age of four should avoid exposure to schistosomiasis.

Tips for Ways to Enjoy the Lake and Avoid Exposure:
  1. Instead of swimming and playing in the Lake, play in chlorinated swimming pools.
  2. Don’t bathe children in Lake water unless it has rested in a storage tank for one to two days or the water has come to a full rolling boil.
  3. Bring an inflatable kiddie pool or wash basin and fill it with water that has been in a storage tank for a couple of days or water that has been boiled and cooled.  You’ll get to enjoy the Lakeside view as your little one splashes and plays.  Be sure to bring fun containers and toys to play with in the pool.

Photograph by Zaitun Arif

Ways to minimize exposure:

  1. Limit the amount of time in the Lake water.
  2. Swim or play in areas that have fast moving water where snails are less likely to live.
  3. Avoid wading in shallow water close to villages. (Remember that the parasite gets in the body through the skin, so wading counts as exposure.)
  4. While there is not enough scientific evidence to say it is effective, it never hurts to ALSO rigorously dry off skin after swimming and apply insect repellant that has DEET. 

There are several factors involved in making a post exposure treatment plan.  The following should be discussed with your doctor: 

Under 4 years of age: The medicine used for adults and older children is not approved for kids under the age of four. Therefore, if your child has had significant exposure or has symptoms of schistosomiasis, she should be treated only under the supervision of your healthcare provider. Your doctor will discuss with you the risks and benefits of treating or watchful waiting. Avoiding schistosomiasis is the best option for kids under four.

School age children: The World Health Organization is battling schistosomiasis through mass drug administration with Praziquantel targeted to school age children. In some parts of the world, children receive yearly preventative for schistosomiasis

Amount and type of exposure: Children that are regularly exposed to fresh bodies of water but are not getting the routine preventative, should talk to their health care provider about getting weight-based preventative.

Minimal exposure in fast moving water may be watched.

Even short hiking expeditions into streams and rivers have resulted in significant exposure. Places that have more snails are at a higher risk. Places close to villages are at higher risk.

General health and symptoms: 

Let your health care provider know if your child has been exposed to the Lake and has any of the symptoms listed above.  If your child seems to be having some unexplained chronic medical concerns mention any possible exposure to schistosomiasis to your doctor.  Keep in mind that a lot of people never have any symptoms. 

Return to passport country: 

The UK National Healthcare System advises that travelers see a tropical medicine or infectious disease specialist upon return to their home country if they have traveled to an area that has schistosomiasis. Most cases of schistosomiasis were diagnosed in expats that had been living in Africa.  When my family travels back to the United States after being in a place known to have schistosomiasis, I treat my whole family with Praziquantel.  It’s not a bad idea for visitors and expats to see a healthcare provider before leaving Malawi to make a post exposure plan.

Photograph by Zaitun Arif

A health care provider should oversee post exposure treatment:

The treatment for schistosomiasis is weight-based, so it is important that your health care provider calculate the correct dose for your growing child. 

There may be a brand that your doctor prefers to use. 

The medicine for treatment can cause headache, dizziness, nausea, vomiting, and general “yucky” feeling, so you want to discuss a treatment plan that works with these side effects. When possible take the medicine at night or at least when you have a day off to feel “sick”. 

Praziquantel is NOT effective against the larvae, so it must be taken at least six weeks to three months after exposure to effectively treat the adult worms. 

Photograph by Krish Maharaul

Information retrieved on November 3, 2020: 

from https://www.cdc.gov/parasites/schistosomiasis/gen_info/faqs.html

from https://www.nhs.uk/conditions/schistosomiasis/

from https://travelhealthpro.org.uk/factsheet/28/schistosomiasis

from https://www.who.int/news-room/fact-sheets/detail/schistosomiasis

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