Onchocerciasis, also known as river blindness, may now be detectable through a urine diagnostic developed by investigators from the Scripps Research Institute. The test, a lateral flow immunoassay (LFIA) diagnostic, can detect the parasitic worms that cause the rare disease, possibly providing a diagnosis in real time.
"River blindness affects individuals both in Africa and Latin America, and because many of these endemic regions are difficult to access, what is needed in the field is an inexpensive point-of-care means to monitor the disease," Kim Janda, PhD, the Ely R. Callaway Jr. Professor of Chemistry and member of the Skaggs Institute for Chemical Biology at Scripps Research, said in a recent statement.
Monitoring and evaluation is key when it comes to current elimination efforts for onchocerciasis—interruption of disease transmission indicates that efforts are working.
Currently, a “skin snip” biopsy is the current gold standard for detecting the parasitic worms; however, they are usually insensitive indicators of infection; as the density of microfilaria in the skin decreases, the sensitivity of the skin snip decreases. Other available tests are unable to distinguish between past and current infections.
The assay uses designer antibodies that are able to detect a unique biomarker—N-acetyl-tyramine-O-glucuronide (NATOG)—which only appears when a human host has metabolized tyramine—a worm neurotransmitter. Humans secret this biomarker in their urine. If a test comes back without any lines, the individual has the parasite; a negative test will show a colored line.
The discovery of NATOG as biomarker for onchocerciasis was previously reported in human urine samples. NATOG bypasses the limitations of antibody biomarkers and PCR methodologies with its ability to distinguish between active and past infections.
In the recent study
conducted by the research team, the NATOG-based urine LFIA for onchocerciasis accurately identified 85% of analyzed patient samples (N = 27).
The novel, noninvasive test is unlike the skin snip biopsy in that it uses a metabolite produced by adult worms, Dr. Janda explains. The inexpensive design of the dipstick coupled with smartphone apps, could offer automatic image processing, according to a recent news release. As such, the new assay may help address critical gaps in the surveillance and treatment of onchocerciasis.
“The work took 11 years to accomplish as the dipstick needed to be inexpensive, robust, and simple to use. River blindness affects millions of people and there was no simple test to monitor its control and hopeful elimination. This dipstick test will help these much-needed tasks,” Dr. Janda told Rare Disease Report®.
This past June, the US Food and Drug Administration (FDA) approved moxidectin
8 mg oral for the treatment of onchocerciasis in patients aged 12 years and older.