San Francisco — An inexpensive dye could give some of the world’s poorest people an early warning if they are infected with deadly parasites.
The dye reacts with a molecule produced by trypanosomes, the microbes that cause leishmaniasis, Chagas disease and sleeping sickness. If the patient is infected, the chemical turns fluorescent green and glows brightly under a blacklight.
“Early diagnosis is the key to improving treatment of these diseases,” said Ellen Beaulieu, a chemist at SRI International who helped to develop the dye, March 21 here at the meeting of the American Chemical Society. “Diagnosis with conventional tests is difficult in developing countries where these diseases occur.”
Trypanosomes infect millions of people each year, and sicken great numbers of livestock as well. As far as parasitic diseases go, the death toll from trypanosome infections is second only to malaria.
Many of the medical lab tests that we take for granted require expensive equipment, refrigerated blood samples, high-end microscopes and trained personnel. In the developing world, it’s hard to find any of those things.
The new test could be performed by unskilled personnel anywhere, in just a few minutes, with little more than an ultraviolet flashlight.
Health care workers could use strips of paper coated with the dye to diagnose people with all three trypanosomal diseases. To find out if their patient is infected, they would add a reducing agent to a bit of serum and then dunk the test strip into that mixture. If the paper glows with a fluorescent green hue when placed under a blacklight, the person is infected and should get antiparasitic drugs immediately.
Until recently, leishmaniasis was mostly a plague of the developing world, but quite a few soldiers picked up the disease while serving in Iraq, and immigrants have been bringing it to the United States.
“There is a concern that [leshmaniasis] is getting into the blood supply,” said Mary Tanga, a medicinal chemist from SRI international. “And soon blood donations will have to be tested for leishmaniasis.”
The test is still in an early stage of development and may not be used in the field until 2015, Beaulieu said. It should be put through a rigorous battery of tests to make sure it’s sensitive and accurate enough.
Image: Shine a blacklight on the dye alone, and it is almost perfectly clear. Mix it with a peptide that is produced by parasites, and it will turn fluorescent green./Elizabeth Wilson
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