healthHealth and Medicine

Volunteers Are Being Infected With A Parasite That Has No Guaranteed Cure

The volunteers are only being infected with male worms, such as the one shown here

The volunteers are only being infected with male worms, such as the one shown here. Jubal Harshaw/Shutterstock

In a laboratory in Holland, volunteers are signing up to be infected with a parasitic worm – and there is a chance they might not be cured of it.

The experiment is part of research to develop new treatments for the parasitic worm that causes the disease schistosomiasis, reports Science. It is caused by up to five different blood flukes that belong to the genus Schistosoma, and is particularly common in poor and rural communities.


The disease causes a variety of symptoms, including abdominal pain, diarrhea, enlarged liver, hypertension, and blood in one's stool and urine. The 17 people that have signed up so far will be infected with male worms so that they cannot lay eggs – the main cause of the disease's symptoms – but some doctors are concerned that there is no guarantee that the patients will be cured of the disease once the experiment is over.

The team, which will carry out the study at Leiden University Medical Center, hope that the research will aid in the development of a vaccine to treat the disease. At present there is only one drug that works, but even that is inadequate. By doing experiments in the lab, the team hope to get better results than what could be achieved in the field.

Schistosomiasis – also known variously as snail fever and bilharzia – is a neglected disease that is prevalent in tropical countries. Most commonly found in Africa, but also present in both Asia and South America, it is thought that up to 700 million people in 70 different countries are at risk of being infected by the parasite.

The parasite gets into people by piercing their skin and entering their circulatory system, where they swim around until they mature and mate, often heading towards the liver. At this stage, the females lay their eggs, which make it into either the intestine or bladder. When an infected person then goes to the toilet in freshwater, the eggs are excreted and hatch. These then find their way into freshwater snails and molluscs, where they develop further before being released to find another human host.   


Because of this reliance on freshwater molluscs, the parasites primarily infect children who are likely to play in infected water, as well as fishermen and farmers who are frequently in rivers and lakes.

It is precisely because the parasite largely infect poor children and fishermen in developing countries that the disease is neglected. It is hoped that this experiment will help to show that humans can be safely infected with the worms in an experimental setting, which will then lead to more vaccines that can be tested.

[H/T: Science Magazine]


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