Rapid diagnosis of onchocerciasis using urinary biomarkers

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Onchocerciasis or river blindness is a parasitic disease affecting 17 million in sub-Saharan Africa. It causes visual impairment, sometimes leading to irreversible blindness, and intense itching of the skin. The symptoms of the disease can be controlled by annual treatment with the drug ivermectin, which kills the larval stages in the skin, but the adult worms are not eliminated and can survive for more than 10 years.Diagnosis of the disease has been dependent for many decades on microscopic examination of skin snips for the larval stage. This is a painful procedure that, not surprisingly, is being met with reduced compliance in communities that have been sampled repeatedly over many years.In this proposal, we aim to radically improve the diagnosis of onchocerciasis by testing for the presence of adult worms using a patient's urine sample. We have discovered that the worms release proteins and small RNA molecules into urine that can be detected by mass spectrometers and sequencing technology. The molecules are associated with small "packets" called extracellular vesicles. We will isolate these vesicles from urine samples to identify the best markers for the disease. To facilitate the process, we will also test urine samples from African cattle, which are infected with a parasite very closely related to that which causes human onchocerciasis. By treating the cattle with drugs that kill the adult parasites, we will test whether the molecules released in urine are a good indicator of whether live worms remain in the host's body. This is a particularly important at the present time, as several drugs with potential activity against adult worms are being tested in clinical trials in humans, and currently the only way to know whether the worms have been killed is to perform surgery on the volunteers.In the final stages of the proposal, we will investigate methods to capture parasite molecules from urine in an efficient manner. This will be necessary to move away from a diagnostic test that is dependent on expensive laboratory equipment to a kit that ultimately could be used in rural Africa.