You may not have realized it, but you quite possibly have a video microscope in your pocket with the potential to indicate treatment for hundreds of thousands of blind individuals throughout the world and millions more at risk for blindness. All you need is an app and a handheld device you could probably assemble in your basement with $100 in parts. And a ticket to sub-Saharan Africa, where most of the need is.
The second leading cause of infectious blindness in the world is river blindness, or onchocerciasis, caused by a parasitic worm transmitted through bites from blackflies that live and breed near fast-flowing rivers. The World Health Organization estimates at least 25 million people have the infection, primarily among 30 sub-Saharan African countries, with a couple pockets of Latin America and the Middle East. Among those infected, 300,000 are blind and 800,000 have some visual impairment, and another 123 million people are at risk for infection.
But there’s a hitch.
Ivermectin is actually so good at killing Loa loa worms that killing them all at once in someone with too many in their blood – more than 30,000 parasites per milliliter – can potentially cause fatal encephalopathy, said Daniel Fletcher, a professor of bioengineering at the University of California at Berkeley. The drug kills all three parasites, but it can kill the person too.
This risk has slowed or even suspended ivermectin administration programs because each person infected with river blindness or lymphatic filariasis has to be tested for Loa loa first to determine whether they can safely take the drug. That testing requires a trained technician using a conventional light microscope to manually count the Loa loa larvae in a blood smear, a process that usually takes at least a day. For millions of people.
But Fletcher and his colleagues have invented a simple device composed of a 3D-printed plastic base, with LED lights, micro controllers, gears, circuitry and a USB port, which can turn a smartphone into CellScope Loa, a mobile phone video microscope that can be used to count Loa loa worms in a blood sample in a few minutes. After a quick fingerprick, the blood sample is placed under the phone’s camera lens. An algorithm analyzes the larvae wiggling in the blood and tallies the total Loa loa worms in just two minutes. (Watch the video below to see a demo.) Since the app prompts the user each step of the way, little training is needed. Though this device uses an iPhone, a similar setup could be built for other smartphones.
How does the app identify the right critters in the blood when the person has other parasites as well? The Loa loa worms only venture out from the lungs into the bloodstream a few hours a day and at different times than the river blindness worms, Fletcher said. “By measuring at specific times, between 10 a.m. and 2 p.m., we can have increased confidence that we’re measuring Loa,” he said. “In addition, other moving things in blood like trypanosomes are much smaller than Loa, so we can look for particular sizes to further increase confidence.”
A proof-of-concept study published yesterday in the journal Science Translational Medicine found that the app’s count is, in fact, pretty accurate. Fletcher’s team tested the device on 33 patients in Cameroon and found the phone’s parasite count to approximately match up with the technicians’ count in a head-to-head trial. The CellScope Loa delivered no false negatives (patients with too many worms who were identified as having fewer) and two false positives (patients with a lower worm count identified as having a higher one). That made the device 100% accurate in identifying those with too many worms to receive the drug.
The study group was very small, so more trials are needed, and the cost would need to drop a bit, but Fletcher roughly estimates that about 15 million people living in Loa-endemic areas could safety receive river blindness treatment using this smartphone video microscope.
South Sudanese fisherman Riek Bol, who lost his eyesight to river blindness, pauses with his net along the bank of a stream in Kacnguan in southern Sudan, Nov. 24, 2003. (AP Photo/John Moore)
“This device demonstrates that a mobile phone can serve as the core of a portable, automated diagnostic device that requires minimal user training, opening the possibility of creating more mobile phone-based diagnostics that can increase access to high-quality measurements that could only previously be obtained in clinics or hospitals,” Fletcher said.
This method isn’t a perfect fix, as noted in NPR’s coverage, since river blindness treatment is needed once a year and there are still millions infected with it, but it’s a start for these parasitic infections regarded as “neglected tropical diseases,” which deeply affect quality of life but don’t usually kill people. “These neglected diseases often have existing therapies if the right patients can be identified,” Fletcher said, “and we hope that technology like ours that can help find those patients.”
Watch the device in action here:
Published: 5/07/2015. By Tara Haelle
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