Diagnostic test for schistosomiasis on the horizon

An international research team has made significant progress towards a new diagnostic test for schistosomiasis, which could help the World Health Organization (WHO) achieve its goal of interrupting transmission of the disease and eventually eliminating it. Their work has been published in The Lancet Microbe.

Schistosomiasis, spread by parasitic blood flukes, is prevalent in tropical and subtropical areas. Urogenital schistosomiasis — one of two forms of the disease — affects an estimated 200 million people, causing both acute and chronic illness. It is also considered a risk factor for HIV, especially for women, and is associated with bladder cancer.

“This is a disease of poverty,” said Dr Mark Pearson, a Research Fellow at the Australian Institute of Tropical Health and Medicine at James Cook University and lead researcher on the new study. “Although there are effective drugs available to treat it, it becomes a serious health issue where contaminated drinking water and waterways lead to frequent reinfections.

“To interrupt the spread of the disease, a test needs to be sensitive enough to identify people with low-level infections, who can still pass the parasite on to others when they might not know they’re infected themselves.”

The research team aimed for a test for urogenital schistosomiasis that is non-invasive, can be administered at point of care (by a community health worker, for example) and will deliver a quick result. Their search focused on the proteins that the parasite Schistosoma haematobium produces while resident in the human body.

“Thanks to our collaborators at the University of California, who were able to fit almost a thousand of these proteins on a chip that’s about twice the size of the SIM card in your phone, we were able to work quite efficiently at identifying which proteins were the major targets of antibody responses,” Dr Pearson said. The fluke proteins were screened for antibodies in blood and urine samples that international collaborators had collected in previous studies in Gabon, Tanzania and Zimbabwe.

“Importantly, these included samples taken from populations where we know the infection level was low,” Dr Pearson said. “This enabled us to test whether our proteins were clearly recognised by antibodies from people with light infections, as well as those suffering heavy infections.”

The candidate proteins were also screened through ELISA, a test used since the 1970s to detect antibodies in the blood. Dr Pearson said, “Between the high-tech chips and the old-school approach using ELISA, we narrowed our options down from 992 proteins to just five lead candidates, from which we chose the two that showed the greatest sensitivity.”

The result is a point-of-care test strip, not unlike a pregnancy test, that carries recombinant versions of the chosen proteins and can detect even low-intensity schistosomiasis infections. While the test currently works on serum (blood), Dr Pearson said the next step would be to refine it for use as a urine test.

“This was an international effort, involving researchers from across Africa and Europe, as well as in Australia, the United States and Thailand,” he said. “It represents an important step forward in protecting vulnerable communities from a tiny parasite that does a great deal of harm.”

Image caption: Dr Mark Pearson with Schistosoma haematobium — the parasitic blood flukes that spread schistosomiasis. Image credit: Romy Bullerjahn.

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