Kiwi also died, and the necropsy tissue was positive for PDD. “He introduced a sick bird with PDD into the nursery. He wasn't washing his hands, washing the counters, taking precautions,” Smith says. “So it just spread like wildfire.”

The breeder was worried. He agreed to let Kistler take samples, but only if he could remain anonymous.

On Kistler's first visit, she collected the young red macaw, and she and Smith sampled nearly every organ. At the UCSF lab, Kistler ran the tissue through a polymerase chain reaction (PCR) test she had developed with the ABV genome data. The test can quickly fish out bits of ABV. The brain and digestive tract were marinating in virus. Kistler returned to the compound for another dying bird. Same results.

The breeder panicked. He wanted all the indoor chicks tested. In mid-September, Kistler and Smith arrived armed with vials for blood and a batch of large Q-tips for swabbing the birds' cloaca, or backsides. They started with the African grays and spent three hours wrangling screeching parrots. When Kistler ran the samples at the lab, she found virus in 12 of 46 chicks. She e-mailed the results to the breeder. He never wrote back. The breeder also cut off contact with Smith, his veterinarian for 10 years. “He went into denial,” Smith says.

There were still more casualties. Another client of Smith's, a second breeder, had boarded three hatchlings at the first breeder's house earlier that summer. After the second breeder brought the chicks home, one of them displayed symptoms and died. Kistler and Smith found ABV in 8 of 10 other birds exposed to the dead chick, even though some were asymptomatic. It was the same strain found in the first breeder's birds. The case was a slam dunk. “We linked the strains,” says Ganem. “We proved the birds in the second aviary caught the strain we saw at the first place.”

The second breeder wanted the virus gone, the birds out; she needed to protect her flock. She asked Smith to quarantine the exposed birds. Kistler and Smith watched the birds for a few months, but Smith eventually euthanized all of them to search for virus in their tissues.

Though they were long-time friends, the two breeders no longer talk. The second breeder, who eliminated the virus from her flock, also doesn't want to be identified. “It's one of those things that can severely damage my reputation,” she says. “I'd never sell another bird again.”

DeRisi acknowledges that it is a complex situation. It's a small world and breeders are a close-knit community. “Maybe someday when birds have certificates of health, and you get a test result from an independent testing service before you buy a bird, it will help clear that up.”

DeRisi, Ganem, and Kistler are convinced that ABV causes PDD. In late 2008, Gancz, the Israeli veterinarian collaborating with the HHMI team, injected three cockatiels with an extract from ground-up ABV-infected parrot brain. One rapidly died from severe PDD, and the other two got sick. The group expects to publish its findings in an upcoming issue of the journal Virology.

A host of other questions now come into play. DeRisi wonders where the parrot outbreaks originate. Do wild ducks or geese carry it? “Maybe parrots are just the dead end,” he says. “What about poultry?”

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