To find a vaccination for schistosomiasis, a neglected tropical disease that affected more than 200 million people in 2016, physicians at Leiden University Medical Centre are infecting volunteers with the parasite that causes the disease.
People in countries across the tropical belt, including India, are impacted by schistosomiasis. Only one drug, praziquantel, is available to treat it, and it is not very effective. Meta Roestenberg, the physician leading the study, believes that infecting people with the parasite could speed up the development of a new cure or vaccination.
Schistosomiasis generally infects humans when they come into contact with water that is infected by the parasite. People can be exposed to the disease during routine work involving tasks such as agriculture or domestic chores. The body reacts to the parasite’s eggs, which results in various symptoms and complications. Consequences such as bladder cancer, infertility, kidney damage, etc can develop in the later stages of the disease. In some cases, the disease also results in death.
Being a neglected disease, significant resources have not been allocated to finding a cure for the disease. Studies such as this one which involve deliberate infecting of humans have been performed with malaria, cholera, and flu, but not yet with schistosomiasis. The researchers are aiming to find if this infection model is safe, and later use it to test what vaccination would be effective in preventing the disease.
Before infecting any volunteer, Roestenberg collected different drugs in what she calls “the emergency box” to treat any extreme allergic reaction that may occur. 13 volunteers have been infected so far. The way the study has been designed poses minimal risk to the volunteers. The symptoms of the disease emerge from the eggs of the parasite, which are born in humans when they are infected by both male and female parasites. But Roestenberg is only using males, which means no eggs will be born.
After being infected, the volunteers will be tested every week for the presence of a molecule called CAA in their blood, which is released by the parasite. In future trials, the absence of CAA will indicate that a cure or vaccination has worked and the parasite has died.