Schizophrenia linked to cats

WORLD OF SCIENCE - BOB BROCKIE

Recent surveys point to a connection between a microbial cat disease and human schizophrenia. The microbe is called toxoplasma or "toxo" for short. Most cats carry the bug but it is a silent infection with them, causing them no harm.

Cats spread the microbe when they deposit their urine or droppings in their litter box, in your garden or in the children's sandpit, though you can pick it up by merely handling the cat. Farm animals and birds also carry toxo. Half the deer in New Zealand carry the infection and you can catch it by eating undercooked meat.

Most of us become infected with toxo at some stage in our lives with little or no effect but it's a different matter for foetuses. If a pregnant woman becomes infected, the microbe sometimes makes its way into the brain of the early growing foetus. A recent survey showed that about 2 per cent of pregnant Auckland women had been infected with toxo.

The bug wreaks havoc with brain development but the results don't show up in babies. Not till kids reach teenage years do problems develop – behavioural problems, learning disabilities, mood swings, mental impairment or schizophrenia.

The connection between toxo and schizophrenia has long been suspected because so many schizophrenics recall their family having a cat when they were babies. Several recent surveys have revealed stronger connections. A study of 1.2 million Swedes showed that early foetal infections increased psychoses and schizophrenia in teenagers by 50 per cent.

Hundreds of schizophrenic Danish teenagers were found to have more than their share of early toxo infections. Robert Yolken of Johns Hopkins Children's Center in Baltimore found that kids with early toxo infections were 16 times more likely to have psychotic disorders than those without.

But it was not only toxo infections. Scientists have found good connections between schizophrenia and women who caught the flu in the early stages of their pregnancies. The connection between flu and schizophrenia was first detected after the 1918 influenza pandemic when a "schizophrenic syndrome" was reported among victims afflicted by acute infections of the disease.

Later the American psychiatrist Alan Brown showed that if women caught the flu early in pregnancy, it increased their chances of producing schizophrenic teenagers seven-fold.

Catching German measles in early pregnancy also increases a woman's chance of producing a schizophrenic child while mumps and herpes are also under suspicion. A curious thing about toxo is that it makes rats and mice less fearful of cats. This makes them more likely to approach and be eaten by a cat – a clever strategy on the part of the microbe to ensure its transmission from host to host. The parasite can also subtly alter human personality, making some men more cautious and some women more kind and open- hearted. There are genes that predispose you to schizophrenia but it seems that cats and toxo give them an extra push.

- © Fairfax NZ News