The ViroChip, which DeRisi and Ganem developed, is a high-throughput screening technology that uses a DNA microarray to test viral samples. The team was able to recover virus sequence from a total of 16 diseased birds from two different continents. The complete genome sequence of one isolate was captured using ultra deep sequencing.
The virus they identified is highly divergent from all previously identified members of the Bornaviridae family and represents the first full-length bornavirus genome ever cloned directly from avian tissue. Analysis of the Avian Bornavirus genome revealed at least five distinct varieties.
PDD is a fatal disease that causes nervous system disorders in both domesticated and wild birds in the psittacine, or parrot, family worldwide. The disease has been found in 50 different species of parrots, as well as five other orders of birds, and is widely considered to be the greatest threat to captive breeding of birds in this family, the researchers said.
The disorder often leads to the birds' inability to swallow and digest food, with resulting wasting; many birds also suffer from neurologic symptoms such as imbalance and lack of coordination. Regardless of the clinical course the disease takes, it is often fatal.
Scientists have theorized for decades that a viral pathogen was the source of the disease, but until now, no one had been able to identify the likely culprit.
"This provides a very compelling lead in the long-standing search for a viral cause of PDD," Ganem said. "With the development of molecular clones and diagnostic tests for ABV, we can now begin to explore both the epidemiology of the virus and how it is linked to the disease state."
|Contact: Kristen Bole|
University of California - San Francisco