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 of infectious diseases 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," he said.
About 40 per cent of New Zealanders are infected with toxoplasmosis, which is transmitted to humans through cat faeces.
It begins with an acute phase typically lasting six to eight weeks, and then invariably develops into a chronic infection which doesn't have obvious symptoms and cannot be cured.
Most people with chronic toxoplasmosis will be oblivious that they have it and it may never cause any problems.
"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, from the Department of Molecular Medicine and Pathology.
But of the 31 patients who took part in the study, 90 per cent reported fatigue during the acute phase 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."
Toxoplasmosis can be particularly harmful to unborn babies if mothers contract it while they are pregnant, as actor Jodie Rimmer found out.
"If a baby gets it in the womb when it's growing in the first trimester it's likely to not grow a brain and if you find out you've got it in the first trimester it is very advisable to terminate," Rimmer said.
"If a woman is to get it in the second trimester the baby is likely to be blind or deaf or have a lifetime of seizures or neurological problems."
Rimmer believed she contracted the disease from a piece of lettuce, fortunately in the third trimester, and it did not appear to have had any effect on her baby, Theo Riley, who is now 9 months old.
However, he has to take antibiotics for the first year of his life and risks health effects later on.
"I actually knew about toxoplasmosis and I still got it so it goes to show you how full-on it is. I knew not to go gardening without gloves on because of cat faeces, and to thoroughly wash all the food I ate," Rimmer said.
The "horrifying" experience had made her think differently about cats.
"With this cat debate recently it's fine to look after the native birds but toxoplasmosis is everywhere. It means, for a pregnant woman, that you can't eat out at a restaurant for nine months, you can't eat at a friend's house, you and your partner are the only ones that can be trusted to serve you food."
Professor Thomas said the study, published in the Scandinavian Journal of Infectious Diseases, pointed to the need for further research on the effects of toxoplasmosis infection on the brain.