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Amy Kistler knows more about birds than she ever intended when she joined the Ganem and DeRisi labs. Her research on a deadly avian virus helped solve a 30-year puzzle and opened her eyes to veterinary research.
Behind the house, dozens of cages—some as big as 6 feet square and 8 feet tall, with wooden nesting boxes inside—littered the yard. Each held a pair of parrots. Majestic macaws, big cream-colored crested cockatoos, African grays with blood-red tails.
As the owner showed Kistler around, the birds screamed and shrieked—a cawing cacophony. “There were more than 100 birds, and they absolutely flipped out,” Kistler says. “I had never seen anything like it before.”
Ignoring the riot, the owner explained the situation: A young macaw was sick. It had stopped eating and was losing weight. During the past six weeks, other parrots in his collection, mostly chicks that lived inside the house, had wasted to the bone and died. Kistler collected the red bird, put its carrier in the backseat of her car, and drove to a local bird veterinarian, Jeanne Smith.
At Smith's office, the pair euthanized the sick bird and opened it up. Smith pointed to one of the digestive organs, the proventriculus. Situated in the upper gastrointestinal tract of birds, the proventriculus normally passes partially digested food farther down the line. In this macaw, though, the organ was grotesquely swollen and clogged with food. This young bird had PDD, proventricular dilatation disease. This and the other dead birds meant an outbreak was spreading.
PDD is the AIDS of the parrot world, devastating captive flocks and stigmatizing breeders whose birds carry it. How Kistler, a virology postdoctoral fellow at the University of California, San Francisco (UCSF), got involved is a story of DNA chips, perseverance, and good timing.
When she arrived at UCSF in 2003, Kistler had never heard of PDD, let alone touched a bird. She had signed on for a postdoctoral position with two HHMI investigators, Joseph DeRisi and Don Ganem, attracted to the operation they had built to link viruses to human diseases. (See “Modern Day Virus Hunters,” HHMI Bulletin, August 2006.) Ganem, the physician of the operation, had found in the late 1990s that human herpesvirus 8 causes Kaposi's sarcoma, a tumor found in many AIDS patients. DeRisi, the lab polymath, is a pioneer in DNA microarrays—glass slides spotted with thousands of genetic fragments.
In 2002, DeRisi and David Wang, a postdoctoral fellow in his lab at the time, invented the Virochip, a DNA array for detecting every virus found in plants, animals, insects, and humans. The Virochip can also identify unknown viruses if they share a smattering of genetic code with a known virus.
In 2003, the Virochip pinned severe acute respiratory syndrome (SARS) on a previously unknown coronavirus, proving the worth of the chip in a pressure-cooker international outbreak that killed hundreds of people.
Photo: Lenny Gonzalez