Humans at risk from disease spread by cats

A disease carried by cats commonly thought of as "benign" and "trivial" can be much more debilitating than previously believed, University of Auckland researchers have found.

Associate Professor Mark Thomas and his colleagues investigated the "neuropsychiatric" effects of acute toxoplasmosis and found this wasn't the case.

"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."

About 40 per cent of New Zealanders are infected with toxoplasmosis at some point in their lives. It begins with an acute phase typically lasting six to eight weeks, and can develop into a chronic infection which doesn't have obvious symptoms and cannot be cured.

"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," said Professor Thomas.

But of the 31 patients who took part in the study, 90 per cent reported fatigue which persisted for a median of six weeks, 74 per cent reported headaches and 52 per cent found they had difficulty concentrating.

Sixteen of the 31 had aches in their muscles and 12 had fever. One was briefly admitted to hospital because of fever, sweats, muscle aches and an elevated heart rate.

"Most respondents reported that these effects had a significant impact on their overall physical and mental health."

Dr Thomas said the study points to the need for further research on the effects of toxoplasmosis infection on the brain.

Studies of laboratory animals with toxoplasmosis have shown it releases dopamine - an important brain messenger molecule - and he suspected that some of the effects of acute and chronic toxoplasmosis in humans may be due to production of excessive amounts of the chemical.


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