Schistosomiasis (Bilharzia): Symptoms, Prevention and UK Travel Advice

Schistosomiasis, also commonly known as Bilharzia, is a parasitic infection caused by schistosome worms. According to the NHS, it is one of the most common parasitic diseases in the world, particularly affecting those who travel to or live in tropical and subtropical climates. The infection is not found in the United Kingdom, but it is a significant consideration for British holidaymakers, backpackers, and those visiting friends and relatives abroad.

The parasite is carried by certain types of freshwater snails. The snails release the larvae into the water, where they can penetrate human skin during contact. Once inside the body, the larvae develop into adult worms that live in the blood vessels, where the females produce eggs. Some of these eggs travel to the bladder or intestines to be passed out in urine or stool, while others become trapped in body tissues, causing immune reactions and organ damage over time.

Many people do not experience any symptoms when they are first infected. However, within hours of the parasite entering the skin, some individuals may develop a localized, itchy rash often referred to as 'swimmer’s itch'.

A few weeks later, a more systemic reaction known as Katayama fever may occur. This is an acute response to the larvae moving through the body and the start of egg production. Symptoms include:

• High temperature (fever) and chills
• A dry cough
• Muscle and joint aches
• Abdominal pain and diarrhoea
• A general sense of feeling unwell (malaise)

If left untreated, chronic schistosomiasis can develop months or years later. This occurs as a result of the body’s immune system reacting to the trapped eggs, potentially leading to inflammation and scarring of the liver, bladder, or intestines.

Before booking a trip, it is vital to check the latest travel health advice. Schistosomiasis is most prevalent in areas with poor sanitation where freshwater is contaminated by human waste. The highest risk regions include:

• Africa: Particularly the Great Lakes region (e.g., Lake Malawi and Lake Victoria) and the Nile River valley.
• South America: Parts of Brazil, Suriname, and Venezuela.
• Asia: Southern China, the Philippines, and parts of Southeast Asia (e.g., the Mekong River).
• Middle East: Parts of the Arabian Peninsula.

Even if the water looks clear and is a popular spot for tourists, the risk of Bilharzia remains if the specific snails are present. NICE guidance suggests that any freshwater contact in endemic areas should be treated as a potential exposure.

Unlike malaria, there is no vaccine or preventative tablet for schistosomiasis. Prevention is entirely based on behaviour while abroad. The most effective ways to protect yourself include:

Avoid Freshwater Contact

The only way to be 100% safe is to avoid swimming, wading, or washing in freshwater lakes, rivers, or streams. Stick to chlorinated swimming pools or the sea, as the parasite cannot survive in salty or properly treated water.

Treat Your Water

If you must use freshwater for washing, ensure it has been boiled for at least one minute and allowed to cool. Filtering water through a fine mesh may help, but boiling is the gold standard. Storing water in a tank for 48 hours before use can also kill the larvae, as they cannot survive long without a host.

Dry Yourself Vigorously

If you accidentally come into contact with potentially contaminated water, dry yourself immediately and vigorously with a towel. This may help prevent the larvae from penetrating the skin, although it is not a guaranteed method of prevention.

If you have recently returned to the UK from a tropical region and spent time in freshwater, you should monitor your health closely. You may wish to speak to a GP online if you develop a persistent fever, skin rash, or digestive issues within three months of your return.

An online GP consultation is a convenient way to discuss your travel history and symptoms from the comfort of your home. The doctor can review your risk factors and, if necessary, advise on the appropriate blood or stool tests required for diagnosis. In the UK, diagnosis is typically confirmed by detecting eggs in a sample or identifying antibodies in the blood. It is important to wait at least 6 to 12 weeks after your last exposure before having a blood test, as it takes time for antibodies to become detectable.

Treatment for schistosomiasis is generally straightforward and highly effective. The primary medication used is Praziquantel. This is usually administered as a short course of tablets, sometimes taken in a single day or over two days.

Praziquantel works by killing the adult worms, allowing the body to clear the infection. While the medication kills the worms, it does not necessarily reverse damage already caused to organs in chronic cases, which is why early detection and treatment are essential. Following treatment, a follow-up test may be required to ensure all parasites have been eradicated.