Tuesday, July 08, 2003

By Michael Woods, Post-Gazette National Bureau

WASHINGTON -- The seemingly far-fetched idea that people might catch a mental illness in the same way they catch the flu gained credence yesterday as scientists reported witnessing in mice a mechanism by which a virus could cause mental disorders.

"Our results suggest that viral infection may play a role in the development of psychiatric disorders," said Dr. Keizo Tomonago, a member of a Japanese research team whose study on Borna Disease Virus was published in yesterday's weekly journal of The National Academy of Sciences.

Dr. W. Ian Lipkin, a Columbia University authority on borna virus, called the Japanese research "elegant." Lipkin was the first to isolate the borna virus from human brain tissue, and he headed the lab that deciphered the virus's genome.

"Mental disorders represent four of the 10 leading causes of disability in individuals over the age of five years," Lipkin said. "Despite progress in identifying susceptibility genes, the causes of most mental disorders remains unknown."

The borna virus has long been suspected as a cause of clinical depression, hyperactivity, schizophrenia and other mental illnesses.

Researchers have found, for instance, that borna virus infections are more common in people with mental illness than in healthy people. Children of mothers exposed to the virus during pregnancy have an increased risk of autism and schizophrenia, as well.

Nevertheless, Lipkin said, more research is needed to prove that the borna virus actually causes such conditions, rather than just being an innocent bystander, and few scientists believe that borna virus alone could cause mental illness.

Tomonago, a virologist at Osaka University, echoed those reservations in an interview from Japan.

"At present, there is no direct evidence that this virus infection links to a specific human disorder," he said. "Although the broad potential host range of this virus suggests that humans are targets for infection, the sources and routes of human infection are not clear now."

Borna Disease Virus was named after Borna, a town in southern Germany where an epidemic killed horses and sheep in the 1880s. People called it "sad horse disease" because depression is among the first symptoms.

The virus also can infect birds, rats, monkeys, cows, rabbits, cats, dogs and other animals, including humans. Scientists think the virus is transmitted much like cold and flu viruses, via infected saliva and mucus.

Infected animals develop symptoms similar to human psychiatric illnesses. Young infected rats become hyperactive, for instance, and rat pups cannot communicate normally -- a condition similar to autism. Other infected animals become violent.

"These observations suggest that BDV is a human pathogen and that viral infection may play a role in the induction of certain human mental illnesses," Tomonago said.

Michael Woods can be reached at mwoods@nationalpress.com or 1-202-662-7072.