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Buttressed by Ganem's findings and the enthusiasm of Kistler and Alexander Greninger, an M.D./Ph.D. student who joined the project, the team decided to make PDD the first veterinary disease they would study with the Virochip. Clubb sent tissue from birds that died of PDD and birds that died of natural causes. The writer of the second letter, an Israeli veterinarian named Ady Gancz, sent his own samples.
In January 2007, Kistler selected one of the samples Clubb had sent from Florida, extracted the genetic material, added fluorescent tags, and then washed the mixture over the Virochip. She slipped the chip into a scanner, which reads each of its 20,000 spots, and watched bright dots scroll up the screen: green spots are hits, white spots are strong hits.
Kistler noticed a white spot on the right edge, one she'd never seen in the hundreds of human disease Virochips she had processed. The computer identified it as “bornavirus.” She'd never heard of it. An Internet search revealed that “Borna disease virus,” named for the town in Germany where a peculiar outbreak in horses was first described in 1885, causes poor balance, motor control problems, and abnormal behavior in horses, sheep, and other livestock. The virus latches onto nerves and can cause encephalitis.
The association to PDD was striking. Five of the eight samples, but none of the controls, lit up with bornavirus.
“That was it,” says DeRisi, recalling when he and Kistler watched the first data roll in. “That was a thrilling moment. It gave us an answer that was pretty clear cut.” In two days, the team and their Virochip had solved a 30-year mystery.
Next, Kistler fished out segments of the virus's genetic code. The segments confirmed that they had found a bornavirus unlike any seen before. The viruses recovered from horses and sheep all closely resembled each other at the genetic level, but the parrot viruses looked much different from those viruses and from each other. The team called them avian bornaviruses (ABVs). After analyzing samples from more dead birds, the team discovered five ABV subtypes across a range of parrot species. Kistler, Ganem, and DeRisi eventually spelled out the entire genome—all six genes—of one strain of the new virus. They had found their quarry.
The team published the discoveries in Virology Journal in July 2008. “We became rock stars of the parrot world,” Ganem says. Soon the calls began. Veterinarians asked if a diagnostic test was available. (“Nothing commercially available.”) Breeders hoped the discovery somehow meant a cure was at hand. (“Not yet.”)
That's when bird doctor Jeanne Smith called. She suspected an active PDD outbreak. Did the researchers want to play disease detective? At this point, Kistler had worked only with tissue samples from dead parrots. She jumped at a chance to investigate live cases, and on that scorching Friday in August 2008, she drove three hours and met Smith at the breeder's compound.
The facts of the case: Several months earlier, a female African gray named Kiwi had fallen ill, lost weight, and developed a nasty fungal skin infection. The breeder isolated Kiwi outside, but brought her inside to the kitchen to medicate her. Too close, it turned out, to where he kept the hatchlings, 50 chicks, stacked in cages in the erstwhile living room and dining room and in the pantry, next to the kitchen. In July, some of the chicks started showing symptoms; a few quickly died.