Scientists in Portugal and Angola have discovered a fast, non-invasive way to test for a cancer-causing parasite that kills hundreds of thousands of people every year. The two teams have also made important discoveries on hormonal changes and mutations caused by this infection.
The parasite Schistosoma haematobium is contracted through contaminated waters when parasite larvae released by infected snails enter the blood vessels via the skin, where they can live for up to 5 years. During that period, the larvae release eggs, which - when excreted to the outside - again infect snails and initiate a new life cycle of parasites.
However, rather than being excreted out, many eggs get stuck on tissues and organs, resulting in schistosomiasis. This triggers immune attacks that also destroy the surrounding tissue. Most often, the urogenital system is affected, where the disease can cause bladder cancer.
In terms of public health, experts consider only malaria to have a more devastating impact in developing countries. Schistosomiasis is endemic in 76 of the poorest countries in the world.
About 243 million people are infected with the disease, which kills about 200,000 people every year. Following infection, women often contract female genital schistosomiasis, which affects the cervix and uterus. Female genital schistosomiasis results in bleeding and pain during sex and infertility.
Screening the urine of women at risk of infection for catechols is a quick, non-invasive test that will improve public health in endemic regions.
Until recently, experts thought that infertility and bladder cancer arising from this infection were byproducts of the immune system attacking the parasite eggs trapped inside the body. The team responsible for the new research has now shown that estrogen-like molecules are produced by the parasite, which they say could be responsible for encouraging cancer development.
The researchers wondered if these molecules, called catechols, may also be responsible for infertility in women with schistosomiasis. Enlisting the help of fertility specialists, they analyzed the urine from 93 women in a region of Angola where the S. haematobium parasite is endemic.
They discovered catechols in the urine of women who tested positively for parasite eggs, but not in the urine of uninfected women. The researchers also found an association between catechols and infertility.
Studying the mechanisms involved, the team found that the catechols "down-regulate" estrogen receptors and trigger DNA mutations. Either or both of these actions could be responsible for the bladder cancer and infertility common to schistosomiasis patients.
Explaining their findings, recently published in the journal PLOS ONE, team leader Monica Botelho says:
"Estrogen metabolism/degradation is a normal body process - estrogens are degraded into catechols and these into quinones. But if there are too many quinones (due to an excessive estrogen production or altered metabolism) this can cause DNA damage, because they tend to bind to DNA disturbing it. Now we detect these molecules not only in the serum, but also the urine of patients infected with Schistosoma, while uninfected patients do not have them.
They have been linked before to cancer (thyroid, breast and prostate) and auto-immunity (when the immune system attacks the own body). Now we see them in infertility associated with schistosomiasis infection."
However, Botelho's team have yet to answer the question of why the parasite produces estrogenic molecules at all. Current theories suggest that the molecules may reduce the density of the bladder wall in order to facilitate the escape of the eggs from the body, or that the manipulated hormonal environment better suits the living conditions of the parasite.
While further research will be needed to answer this, more immediate benefits to vulnerable groups are offered by the discovery of the catechols. It is now possible to diagnose infection quickly and easily by screening urine for presence of these molecules, which, the team notes, "should improve the public health in under-resourced and under-served populations."
Written by David McNamee