Smartphones aren't simply an amazing convenience. In Africa they can be used to make a lifesaving diagnosis. In fact, scientists are hoping to use a souped-up smartphone microscope to help them eradicate a devastating disease called river blindness.
Onchocerciasis, as the disease is also known, is caused by a parasite that's spread by flies. Thirty years ago, it was simply devastating in parts of Africa, like Mali.
"We went out to villages where 40 to 50 percent of the adults were blind," says Dr. Gary Weil, a parasitic disease specialist at the Washington University School of Medicine in St. Louis. Worldwide, 300,000 people are blind as a result of this parasite, according to the World Health Organization.
That situation changed dramatically when researchers discovered that a veterinary medicine called ivermectin could prevent river blindness in people. Since 1987, drugmaker Merck has donated more than a billion doses of this drug to fight river blindness and a related disease. The drug is given both as a preventive and after someone is diagnosed.
"The ivermectin has had an amazing effect," Weil says. There's a massive campaign underway to use the drug to eradicate river blindness entirely with an annual dose.
But there's a problem. In some areas, people are also infected by another parasite, a worm called Loa loa. And if someone has a raging Loa loa infection and you give them ivermectin, that can occasionally prove deadly.
The workaround has been to look for Loa loa worms in people before giving them the drug.
"The traditional way of making the measurement involves taking blood smears, looking at them under a conventional microscope by a trained individual, and counting [the worms] manually," says Daniel Fletcher, a bioengineering professor at the University of California, Berkeley. "And that's a far too laborious and long process to be used in a mass drug-administration program, which is what they were running."
Fletcher has been working on novel ways to use iPhones as the centerpiece of inexpensive, portable microscopes. One day he got a call from Dr. Thomas Nutman at the National Institute of Allergy and Infectious Diseases, asking Fletcher if he could develop a device that could quickly and reliably detect Loa loa in a drop of blood.
The worms don't make this job easy. They hide out in the lungs and "are only present in the bloodstream between 11 a.m. and 1 p.m.," Fletcher says. "The tests all have to be done during that time frame, so being quick is really important."
Fletcher's group at Berkeley set to work and came up with a way to detect the squirming motion of those worms when they emerge and circulate in the blood. They report their advance in the journal Science Translational Medicine.
"The phone does pretty much everything," Fletcher says. A health worker collects a pinprick of blood in a small glass tube and pushes it into a compact and inexpensive microscope adapter that connects to the iPhone.
"You press one button, 'go,' and the phone controls the movement of the sample, controls taking of a video and controls analysis and reporting of the results."
In three minutes, start to finish, the process can tell the health worker whether it's safe to give the person ivermectin. But even producing an answer every three minutes still only translates to 40 results per day per phone, since the tests can be run only during a two-hour period. That's much faster than the conventional method, but the numbers are still daunting.
Weil says it seems useful on a smaller scale, but "I don't see it how it could be scaled up to the scale of tens of millions of people" who currently live in areas where both the Loa loa worm and the river blindness parasite live.
"And it wouldn't just be a one-time test," Weil adds, "since the treatment for river blindness is a once-a-year treatment, every year they would have to be tested."
The real solution, Weil says, is to find a drug that can safely kill both parasites at the same time. Researchers are working on that right now.