Rare Virus may be Linked to Schizophrenia

by Kristy Wooley

Experts think humans may suffer a range of psychiatric and neurological disorders as a result of infection

BALTIMORE -- A virus once thought to infect only horses and sheep may actually cause some cases of human schizophrenia, according to researchers at the University of Maryland School of Medicine. In a presentation at the annual meeting of the Society of Neuroscience, Royce Waltrip, assistant professor of psychiatry and six other researchers from the National Institute of Mental Health and the Johns Hopkins School of Medicine, reported finding antibodies to the Borna disease virus in blood samples from nine out of 25 schizophrenic twins in a cohort taking part in a NIMH study. By examining sets of identical twins who either both had schizophrenia or manic depressive disorder, and sets of identical twins, one with mental illness and one without, the researchers tried to separate the effects of genetics from the environment. Waltrip says the contrasting twin pairs were less likely to have a genetic form of schizophrenia. Previous researchers have tried to find a link between other infections and schizophrenia, but the studies looked at viruses with no specific link to mental disorder. Waltrip thinks the relationship between Borna disease virus and schizophrenia is more logical. "In animals the virus infects the nervous system and behavior either directly or by triggering a response from the immune system. In horses and sheep the immune response leads to severe brain inflammation and eventually death," he says. The severity of the immune system response differs depending on the species, and a wide range of wild and domestic animals are hosts or have been infected with the disease, including primates. "Because of the range of animals that can be infected, and because the range of infection outcomes is variable and sometimes subtle, experts think humans may suffer a range of psychiatric and neurological disorders as a result of infection and could be natural host for the virus," he says. "There are very few leads in schizophrenia research," says William Carpenter, director of the Maryland Psychiatric Research Center and professor of psychiatry in the School of Medicine. "Dr. Waltrip is trying to further define how Borna may be involved in schizophrenia and if it is, which patients have it because of Borna." Waltrip says Borna disease virus has never been identified as a human pathogen, but recent research suggests that humans are infected.

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