Infectious diseases you’ve probably never heard of Part I: SCHISTOSOMIASIS
We’ve all heard of malaria, dengue fever, typhoid fever and hepatitis. These are all common infectious diseases we hear about while traveling, especially in developing countries. But what about the lesser known infectious diseases? Like schistosomiasis?… Shisto-what? Exactly.
What is Shistosomiasis?
Shistosomiasis, also known as Bilharzia, is caused by parasitic worms (helminths). It is spread through contact with fresh water in tropical and subtropical countries, especially in developing countries without proper sanitation and access to safe drinking water. It can be a risk in rivers, ponds, lakes and streams. It is not a risk in saltwater (oceans or seas). Freshwater snails are necessary for part of the parasite’s lifecycle.
The disease occurs when the worm’s larvae penetrate the skin then develop and migrate to veins around the liver or bladder where mature worm pairs begin to produce eggs 1 to 3 months after the parasite enters the body. Adult worms can live for up to 15 years. They produce a large number of eggs that exit the body through the urine or feces.
Are you at risk?
About 85% of the world’s cases are in Africa. Many countries where the disease is common have established control programs, but others have not. Most cases of schistosomiasis acquired during travel occur in sub-Saharan Africa in areas frequently visited by travelers. These areas include Lake Malawi, Lake Tanganyika, Lake Victoria, the Omo River (Ethiopia), the Zambezi River, the Nile River, the Banfora region (Burkina Faso), and areas populated by the Dogon people (Mali). Most freshwater sources in Africa can be a potential source of infection.
Infection in travelers is usually acquired through swimming, rafting, boating or bathing in infected waters in Africa. The larvae can penetrate the skin within 30 seconds and for up to 10 minutes after contact, so even brief exposure in infected waters is a risk.
What are the symptoms?
A few hours after exposure 10% of people experience tingling and a rash where the parasites have entered the body, which usually resolves within 24 hours. Katayama fever occurs weeks later when the adult worms begin to produce eggs. Signs and symptoms of Katayama fever include high fever, malaise and increased white blood cells, often accompanied with cough, wheeze, shortness or breath, diarrhea, swelling of the liver and spleen, and hives. Chronic infections can lead to complications in the bowel, liver, urinary tract and bladder.
Is there treatment?
Schistosomiasis can be treated with the medication Praziquantel. A single course of treatment is usually effective, although a repeat treatment after 2-4 weeks may be needed.
There is no vaccine or medications available to prevent schistosomiasis. The best way to prevent schistosomiasis is to avoid swimming or other contact with freshwater in countries where schistosomiasis is a risk. If water exposure cannot be avoided, then wearing protective footwear and clothing such as rubber boots and wetsuits can prevent infection. The parasites cannot survive drying, so vigorous towel drying of exposed skin and clothing provides some protection. Insect repellents containing DEET can help to prevent the parasites from penetrating the skin, but this may be short-lived and cannot reliably prevent infection. It is safe to swim in chlorinated swimming pools.
So now you’ve learned about schistosomiasis, a Neglected Tropical Disease. Be mindful of your freshwater exposure during your travels, especially in sub-Saharan Africa!
TravelSafe Clinical Educator – Kristin Cain, RN, BSc, MSc(A)
Lake Malawi by Kristin Cain