Blind spot. The parasitic worm Onchocerca volvulus ( insert ) can move the eyes and cause blindness in these
two patients in Guinea-Bissau. Onchocerciasis is considered a neglected tropical disease
Harry Anenden / WHO. (Box) CDC
A small parasitic worm is one of the leading causes of blindness worldwide. But now researchers have discovered a molecule in the urine of African patients could help diagnose those infected with the parasite and help eliminate the devastating disease known as river blindness.
The disease, scientifically known as river blindness, is caused by the parasitic worm Onchocerca volvulus . blackfly bites transmit the larvae of the worm to man, and the larvae become adults who form nodules under the skin all over the body. female worms then produce a large number of larvae called microfilaria that move on the skin to be eaten again by biting black flies. The larvae can also enter the eyes, however, which causes blindness. An estimated 500,000 people, mostly in sub-Saharan Africa, have lost their sight because of the parasite.
The World Health Organization has set a goal of eliminating the disease in the Americas by 2017 and Africa in 2025. Infections with Onchocerca volvulus can be treated with ivermectin, which kills the larvae but not the adult worms. The antibiotic doxycycline, which kills bacteria called Wolbachia which lives in symbiosis with the worm, has shown promise in killing adult worms as well and is sometimes used alone or in combination with ivermectin. current control strategies are based on processing of repeated mass of potential patients with ivermectin, however, the diagnosis is often difficult. In some cases, worms surviving adults may spawn a new generation of larvae.
The gold standard for diagnosis is supposedly snip of skin. "You basically cut off some skin and then you can see the larvae of worms," said Daniel Globisch, researcher at the Scripps Research Institute in San Diego, California, and one of the authors of the study. the method is very sensitive, however, especially in less severe infections, which are becoming more common with the progress in controlling the disease, said Maria-Gloria Basáñez, researcher neglected tropical diseases at Imperial College London .
Now Globisch and colleagues identified a new way to test for the disease. They compared the amounts of hundreds of molecules found in the urine samples of infected and healthy Africans and discovered a difference striking: an unknown molecule was present at six times higher in urine samples of infected people than in samples from healthy people the researchers identified the molecule as the rest of a neurotransmitter that the larval stages. excrete worm and which is then broken down in the body before being excreted in the urine, they report online this week in the Proceedings of the national Academy of sciences.
"Finding such a marker was really lucky," said Globisch. "The use of this molecule, we could do a diagnostic test that can be put in a backpack and diagnose if people are infected or not. "This would allow doctors to" specifically address those still infected, "he said. Globisch believes that such a portable diagnostic test could be ready in 3 years.
the approach of researchers "to identify biomarkers is certainly stylish and innovative," wrote Michel Boussinesq, an expert of onchocerciasis in the research Institute for development in Montpellier, France, in an email. But urine samples may not be easier to collect in an African village that skin snips, he warns. An experienced researcher could collect 40 in an hour skin shears, he said, but with urine, researchers must wait until each person can produce the sample. To ensure that the new technique offers an advantage, "it would be necessary to compare the quantitative results of the technique described in the document, and quantitative results of skin snips," he said.
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