NIH: When it comes to devising new ways to provide state-of-the art medical care to people living in remote areas of the world, smartphones truly are helping scientists get smarter. For example, an NIH-supported team working in Central Africa recently turned an iPhone into a low-cost video microscope capable of quickly testing to see if people infected with a parasitic worm called Loa loa can safely receive a drug intended to protect them from a different, potentially blinding parasitic disease.
As shown in the video above, the iPhone’s camera scans a drop of a person’s blood for the movement of L. loa worms.
Customized software then processes the motion to count the worms (see
the dark circles) in the blood sample and arrive at an estimate of the
body’s total worm load. The higher the worm load, the greater the risk
of developing serious side effects from a drug treatment for river
blindness, also known as onchocerciasis.
This work represents the latest advance
in biomedical research’s long, ongoing battle against river blindness,
which affects about 25 million people in Africa, Latin America, and the
Middle East. Major progress was made starting in the late 1980s, when
the pharmaceutical firm Merck discovered that its drug ivermectin
(Mectizan®) kills the parasitic worm that causes river blindness (Onchocerca volvulus) and then took the bold step of donating an unlimited supply of the drug to needy nations that requested it.
Nearly three decades and a billion pills later, the ivermectin
distribution campaign has made a big difference in fighting river
blindness. Still, in the Republic of Cameroon and other countries in
Central and West Africa, the campaign ran into an unexpected problem: a
small, but significant, fraction of people who received ivermectin fell
severely ill or even died from neurological complications. Researchers
later determined that patients who suffered such adverse reactions not
only were infected with O. volvulus worms, but also had unusually heavy loads of L. loa worms in their bodies. By itself, L. loa infection, called loiasis, usually isn’t serious. However, when large numbers of L. loa worms
are suddenly killed by ivermectin, they incite an inflammatory reaction
that can block tiny blood vessels, leading to devastating complications
in the brain, liver, and other organs.
Laboratory and field-based blood tests exist that can determine which individuals have too many L. loa
worms in their blood to receive ivermectin safely. But due to the
logistics and requirements for trained personnel and sophisticated
equipment, these have proven to be too impractical to administer on a
wide-scale basis in remote areas. So, by the early 2000s, annual
ivermectin treatments to combat river blindness were halted in this area
To get at the problem, Thomas Nutman, an immunologist with NIH’s
National Institute of Allergy and Infectious Diseases (NIAID), and his
colleagues first tried to simplify standard screening tests, with mixed
results. Then, a few years ago, Nutman heard about the work that
bioengineer Daniel Fletcher was doing in adapting smartphones for use as
mobile microscopes. Already, Fletcher’s group at the University of
California, Berkeley had reconfigured smartphones to test for
tuberculosis and malaria, with other applications on the drawing board.
So, the Nutman and Fletcher labs began talking, and their
conversations led to a re-engineered iPhone 5s, which they’ve dubbed
CellScope Loa. What’s innovative about their new screening test is its
reliance on the phone’s built-in video camera and processors.
Here’s how the process works: A person’s finger is pricked and a drop
of his or her blood is loaded into a thin, roughly four-inch
capillary—the equivalent of a glass slide for a standard microscope. The
capillary inserts into a slot on the side of the phone, and the “go”
button is punched. That prompts the phone’s video camera to image the
sample briefly from five different fields of view with the help of two
lenses that have been repositioned to focus on the capillary. An
image-processing algorithm programmed into the phone automatically
identifies disturbances to red blood cells caused by wriggling of
immature L. loa worms, called microfilariae. Based on this
motion detection, the phone estimates the individual’s worm load. If the
count is under 30,000 microfilariae per microliter of blood, a person
can safely receive ivermectin treatment. But if the count is above
30,000, treatment is not recommended due to risk of adverse reactions.
In their pilot study, just published in Science Translational Medicine
, the researchers used CellScope Loa to test 33 people living in the
Republic of Cameroon. Compared to traditional microscopy, CellScope Loa
was successful 94 percent of the time at identifying individuals
eligible for ivermectin treatment, and, most importantly for purposes of
preventing adverse reactions, it was nearly 100 percent successful at
detecting individuals with microfilariae counts above the recommended
level for treatment. In fact, researchers calculated that using their
new smartphone-based test, only 1 in 10 million people at high risk for
adverse reactions would mistakenly receive the green light for
ivermectin treatment. Since the phone is reusable, what’s really nice is
each test costs less than three cents, mainly to cover the cost of the
capillary, swabs, and other testing materials.
Nutman and his colleagues plan to return to the Republic of Cameroon
this summer to use their smartphone test to screen 60,000 people. If
their preliminary findings are confirmed by the larger study, this
system may provide an efficient, cost-effective way to enable resumption
of ivermectin campaigns in Central and West Africa, helping to reduce
the suffering and disability still being caused by river blindness in
this area of the world.