The disease begins with an acute phase lasting typically for six to eight weeks. It continues as a chronic infection, normally without obvious symptoms that cannot be cured and last for life.
“While chronic toxoplasmosis has been shown to have a strong association with conditions affecting the brain such as schizophrenia, and with suicide and self-harming behaviour, the disease in its acute phase has usually been seen as a benign, trivial and self-healing illness,” says Associate Professor Mark Thomas from the university’s Department of Molecular Medicine and Pathology.
His comments follow a questionnaire study completed by 31 adults diagnosed with acute toxo by GPs in Auckland in 2011.
“We were surprised, when the results came in, to discover how common it was for patients to report significant and prolonged symptoms such as impaired memory and concentration, headaches and extreme fatigue.”
Thomas told Rural News the study did not determine whether respondents were rural or urban residents.
“We did ask about cat contact (16/31 respondents) and about gardening with bare hands at least once a week (4/31 respondents).”
While there are probably many reasons for higher rates of suicide and depression in rural populations, Thomas says he couldn’t rule out toxoplasmosis as having some effects.
The few studies of chronic toxoplasmosis incidence in New Zealand hint at increased incidence in rural areas: 60 out of 140 blood donors (43%) tested positive in Waikato in 2005; 163 out of 500 (33%) pregnant women in Auckland in 2004; 340 out of 566 (60%) pregnant women in Hamilton in 1982.
“Perhaps the Waikato and Hamilton samples had higher rates than the Auckland sample because of more rural people in these samples,” Thomas suggests.
Studies of laboratory animals with toxoplasmosis show that the organism releases dopamine – an important brain messenger molecule.
Thomas suspects some human effects of acute and chronic toxoplasmosis may be due to excessive amounts of this.
The Auckland study has been published as a scientific paper in the Scandinavian Journal of Infectious Diseases.
