As part of our research on infectious agents as possible causes of schizophrneia and bipolar disorder (manic-depressive illness), the Stanley Laboraratory for Developmental Neurovirology is also researching how such infectious agents could theoretically be transmitted to humans. Cats are being investigated as one possible reservoir for infections. It should be stressed that at this time we have no proof that cats are involved in causing these diseases, and we are not advocating that anyone avoid contact with their cats or otherwise change their behavior toward cats. We are merely exploring the possibility as one line of research with the goal of developing new methods for disease prevention and treatment.
Why even consider cats at all? There are several reasons to do so:
1. Cats carry at least 30 infectious agents which are known to be transmitted to humans. The best known of these are rabies, the bacteria which causes cat scratch disease, and toxoplasmosis. Some pediatric cancer specialists also suspect that some childhood leukemias may be associated with a virus carried by cats but this has not been proven.
2. Areas of the world in which cats are very common (e.g. Ireland, Scandinavia) have a comparatively high prevalence of schizophrenia and areas in which cats are not common (e.g. Papua New Guinea) have a comparatively low prevalence.
3. Cats being widely kept as housepets is a comparatively recent phenomena, starting in the early-mid 19th century in England and North America. The increased prevalence of cats as housepets coincides temporally with the increased prevalence of schizophrenia and bipolar disorder according to one analysis (see E.F. Torrey and J. Miller, The Invisible Plague: Rising Mental Illness from 1750 to the Present, Rutgers University Press, to be published late 2001).
4. Two studies have reported that individuals with schizophrenia and manic-depressive illness, compared to individuals who do not have these disorders, have had greater exposure to cats in childhood.
5. Some studies have reported that individuals with first-onset schizophrenia have an increase in antibodies to toxoplasmosis.
6. There are case reports in the literature of psychiatric and behavioral abnormalities in some individuals with Toxoplasma infection
7. Some of the medications used for the treatment of schizophrenia have the ability to inhibit toxoplasma in cell culture.
Relevant articles, abstracts and presentations at scientific meetings are linked below.
Could Schizophrenia Be A Viral Zoonosis Transmitted From House Cats? E. Fuller Torrey and Robert H. Yolken, Schizophrenia Bulletin, 1995
The Antecedents of Psychoses: A Case-Control Study of Selected Risk Factors E. Fuller Torrey, R. Rawlings, R.H. Yolken, Schizophrenia Research, 2000.
Antibodies to Toxoplasma Gondii in Individuals With First-Episode Schizophenia. RH Yolken, S. Bachmann, I Ruslanova, E Lillehoj, G Ford, EF Torrey, Clinical Infectious Diseases, 2001
The Control Study of Schizophrenia and Affective Disorders and Toxoplasma Infection. L Qiuying, L Xiaonian, L Li, et al. Acta Academiae Medicinae Hubei, 1999. (TABLES ONLY AT THIS TIME)
PRESENTATIONS AT SCIENTIFIC MEETINGS
MOLECULAR SYSTEMATICS OF TOXOPLASMA GONDII AND RELATED COCCIDIA: EXPANDING THE RANGE OF DISTINGUISHING CHARACTERS FOR TAXONOMY, SYSTEMATICS AND DIAGNOSTICS. John R. Barta, Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada
TOXOPLASMA ANTIBODY TITERS IN TREATMENT NAIVE FIRST EPISODES OF SCHIZOPHRENIA. John Gilmore , University of North Carolina at Chapel Hill, Chapel Hill, NC
ARTICLES IN GENERAL INTEREST PERIODICALS