Isaac Bogoch/Toronto General Hospital

Scientists have used an iPhone and a simple US$8 lens to diagnose intestinal worm infections in rural Tanzania.

A cheap lens, flashlight and a little plastic wrap can turn a smart phone into a field microscope to test children for intestinal worms, researchers reported on Monday.

Microscopes are scarce in the countries where doctors often need them the most to figure out if children -- and often adults, too --are infested with worms that can cause anemia, stunt growth and cause other health problems.

Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital in Canada, had seen reports from scientists who turned their smart phones into microscopes. “There were a couple of papers that showed how certain groups were attaching the little ball lenses to their iPhones in a laboratory setting, and they were saying, ‘Hey, you can magnify specimens pretty easily,’” Bogoch told NBC News.

“We thought that this was a really good idea and we could take this into the field.”

For Bogoch and colleagues, into the field meant Pemba Island in Tanzania, where 199 children were already taking part in a clinical trial for a new treatment against intestinal worms.

“We are looking for very common parasites that affect over a billion people on the planet,” Bogoch says. “If untreated, they can lead to anemia and malnitrution and stunted cognitive and physical development.”

Right now, public health workers often simply guess. “Diagnosing these illnesses is a bit different in resource-poor settings because we apply population-based mass treatments so that only a small sample of the population is diagnosed in order to estimate the prevalence in a given endemic area,” says Dr. Peter Hotez, Dean of the National School of Tropical Medicine at the Baylor College of Medicine in Houston.

The World Health Organization then has guidelines for treating communities en masse if, say, 20 percent or more of those tested have a parasite. But that may mean treating children who don’t need the drugs, or treating them for the wrong parasite.

“Many rural health outposts have no diagnostic capability at all. They have no microscopes,” Bogoch says. “They do the best they can.”

They often simply guess about whether someone’s infested and if so, what with.

Bogoch and his colleagues bought an $8 lens off the Internet and used two-sided tape to attach it to his iPhone. They got stool samples on glass slides from the 199 children, wrapped them in cellophane, and used a flashlight to shine light up through the smear. They used the phone to magnify an image, and looked for parasite eggs.

They found evidence of intestinal worm in 70 percent of the samples that also tested positive using a microscope, the team reported in the American Journal of Tropical Medicine and Hygiene.

The method detected some worms better than others.  The doctors using it detected 81 percent of infections with giant roundworm, A. lumbricoides, and 54 percent of infections with another roundworm, T. trichiura. However, it could help spot only 14 percent of hookworm eggs.

But with a little tweaking, it could still help in places where there’s no diagnostic capability at all, said Hotez. And many people even in very poor countries carry smart phones.

Bogoch says another potential use could be to check blood smears for malaria parasites.

“If we do not have to bring in trained microscopists for this work it makes public health control more straightforward,” said Hotez, who was not involved in the study. “Developing simple hand-held devices could be an advance in the global control of neglected tropical diseases.”

As for the “ick” factor? “Obviously, the stool isn’t in direct contact with the phone,” said Bogoch. “Any time you are going to use it as a phone you will want to wash it down with an alcohol swab.”

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