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Tuesday, September 4, 2012

How your cat could make you suicidal

How your cat could make you suicidal

Scientists believe a disease spread by cats could be more serious for humans than they thought

LAST UPDATED AT 11:24 ON Tue 4 Sep 2012

A DISEASE spread by cats that might cause behavioural changes in some humans and miscarriage in pregnant women is infecting 350,000 people per year in the UK, according to a report to be published by the Food Standards Agency this week.

Some scientists are now calling for the infection - called toxoplasmosis - to become a 'notifiable disease', The Independent reports. This would mean doctors would have to report cases to the government. Scientists also want families with young children to eschew pet cats.

A disease caused by infection by a protozoan - a type of single-celled organism - called Toxoplasma gondii.

Toxoplasma gondii can only complete its lifecycle - in other words, reproduce sexually - in cats. A host cat can transmit millions of toxoplasma 'oocysts' - containing the protozoan's embryo - in its faeces. These oocysts can survive for several years in the soil and be ingested by a variety of organisms, including lambs and humans, who are 'accidental hosts'.

However, for toxoplasma's lifecycle to be completed, it must find its way into a rat or mouse. Toxoplasma causes changes in the host rodent's brain that make it behave in a way which is more likely to lead to its capture by a cat. Toxoplasma's lifecycle is completed when a cat eats an infected rodent.

Scientists suspect that the chemical changes that have been shown to happen in infected rats' brains might also happen in those of humans.

Professor Joanne Webster of Imperial College London told The Independent: "I think what we are going to see in humans is going to be similar to what we see in rats.

"There's going to be these very subtle changes such as slightly decreased reaction times and gender effects between males and females. Most of it will be so subtle we won't see it unless we look very carefully, which goes with it being dismissed as an asymptomatic parasite for so long."

Scientists are still trying to understand the behavioural changes - if any - in humans infected with toxoplasma, but research has so far linked it to worse reaction times, a more than two-fold increase in the risk of being involved in a car accident, suicide in women and schizophrenia.

Jaroslav Flegr of Charles University in Prague, who studied reaction times, said of the car accident findings: "If it is true, then latent toxoplasmosis is the second most important protozoan killer, just after the malaria."

Toxoplasma in pregnant women can affect the development of the foetus and cause a miscarriage. People whose immune systems are deficient, such as those suffering from Aids, can suffer diseases such as the potentially lethal toxoplasmic encephalitis of the brain.

Don't own a cat, for a start. Felines like to defecate in loose soil and sand, so don't let your child near playgrounds where sand pits are kept uncovered. Rare lamb can also carry toxoplasma, and some scientists want the government to advise against eating underdone lamb.

Yes, but at the moment, only patients with obvious symptoms caused by toxoplasma are treated. One treatment, according to the Mayo Clinic, involves Pyrimethamine, a medication used for malaria, taken alongside a course of antibiotics.

In more than 80 per cent of human cases, toxoplasmosis results in no obvious symptoms. However, new research suggests that even among this apparently healthy 80 per cent, toxoplasmosis cause potentially dangerous behavioural changes. · 

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