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A Case of the "Baghdad Boil"

by Jeff Worley

When Staff Sergeant Eric DiVona, from Ft. Campbell, Kentucky, returned from serving nine months in Iraq, he brought along with him an unwelcome souvenir. In an interview in mid-April with AP reporter Stephen Manning, DiVona described how the small bumps on his left earlobe and face kept swelling, one bump growing to the size of a silver dollar.

The condition is common enough in Iraq that soldiers have given it a name: the "Baghdad boil"; its scientific name is leishmaniasis. Doctors at Walter Reed Army Medical Center, where DiVona was treated, reported 653 cases of leishmaniasis by April 19.

Photo of Sam TurcoSam Turco

"I'm not surprised, really, by these numbers," says Sam Turco, a UK professor of biochemistry who has spent 20 years studying the unique characteristics of this rugged and potentially deadly parasite. "This is the peak season for sand fly breeding, and I understand that many soldiers sleep outside at night, which is the sand fly's favorite mealtime."

Leishmania is a survivor. It lives—and thrives—in the gut of a sand fly. When a host sand fly bites a human, and macrophages rush to the site of the bite to fight off the invader, leishmania doesn't care. Engulfed by the mighty macrophages, leishmania makes itself at home and calmly goes about its business of replicating.

"One of the intriguing things about this parasite is its ability to live in the most hostile of environments," Turco says.

Leishmaniasis that remains on the skin causes open, slow-healing and sometimes disfiguring skin sores. If the bug works itself inwards, it can spread to several organs and can cause death if left untreated. About 2 million new cases of leishmaniasis occur each year, primarily in India, Sudan and Afghanistan.

Turco and his colleagues at UK, along with collaborators at Washington University in St. Louis have recently made some important inroads to understanding how this parasite functions.

"We've been looking at various parasite-molecules in this single-cell organism that allow it to survive so well, and we found likely candidates—sugar-coated lipids and sugar-coated proteins," Turco says. In lab tests, when the researchers genetically engineered leishmania to prevent it from making these lipids and proteins, the parasite didn't survive in sand flies or in macrophages. "So we found that these lipids and proteins are essential for the parasite to survive and likely important in enabling disease in humans."

But because of a second discovery about this crafty parasite, this wasn't the end of the road for leishmania.

"We were on the right track, but, unfortunately, we've also discovered 20 different leishmania species," Turco explains, "and our magic sugar-coated lipid and protein bullets appear to work in only some of these. In other species of leishmania, if we knock out these lipids and proteins, the parasite still survives." The research team is currently working to understand the biochemical makeup of these non-affected species, which may be making other specialized molecules to protect themselves.

Turco has given lectures around the world on his parasitic infectious disease research. His current work is being supported through two grants from the National Institute of Allergy and Infectious Diseases, one of which was a prestigious MERIT award.

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