The Lost City of the Monkey God

by Douglas Preston

When our team members were diagnosed, biopsies were taken from our lesions and sent to another lab at NIH, called the Molecular Parasitology Section, where the lab’s director, Michael Grigg, had originally identified the parasite as L. braziliensis by sequencing part of its genome. I called up Grigg to find out if he had found out anything unusual. “The type of leish you have was very hard to grow,” he recalled. In fact, like some difficult strains, it wouldn’t grow at all. He smeared tissue samples from our biopsies on blood agar plates, but the parasites refused to multiply. Because of that, his lab wasn’t able to tease enough parasites clear of human tissue to sequence the entire genome at the time—there was too much human DNA mucking up the works. Instead, he explained, they initially sequenced one gene or marker: a characteristic one that reveals the species. That marker matched braziliensis. But later, Grigg sequenced five markers—which he described as “five little windows into the parasite.” He got a big surprise. In two “windows” he found genetic sequences different from any known species of leish. In another window, he found that the DNA resembled another species called L. panamensis, an equally bad mucosal strain. But that gene also had a couple of mutations. Our parasite, he said, might have been a hybrid between panamensis and braziliensis, in which the two species mingled in a sand fly gut, mated, and produced hybrid offspring. That hybrid was then isolated an...