Science briefs: Cat parasite linked to human suicide risk

  • Updated: July 14, 2012 - 4:37 PM

CAT PARASITE LINKED TO HUMAN SUICIDE RISK

A wily parasite well known for influencing the behavior of its animal hosts appears to play a troubling role in humans, increasing the risk of suicide among women who are infected, new research shows.

Chances are you or someone you know has been infiltrated by the parasite, called Toxoplasma gondii. Researchers estimate that T. gondii is carried by 10 to 20 percent of Americans, who can get it by changing litter used by infected cats or eating undercooked meat from an animal carrying the bug.

The parasite's optimal host is the cat -- it can fully complete its reproductive cycle only in the feline intestinal tract. So T. gondii has developed an ingenious mechanism for survival: It turns rodents into willing cat food. When a rat or a mouse is infected, it suddenly becomes attracted to cats.

But it also seems to prompt behavioral changes in humans, said a Danish study that examined infection rates and suicide attempts in more than 45,000 women tracked for more than 10 years. During that time, 1 percent of the women tried to take their own lives. But women with T. gondii infections were 53 percent more likely to attempt suicide than women who were not infected.

HIGH CALORIC DIET MAY BE HARD ON THE BRAIN

If you're 70 or older and you eat more than about 2,200 calories per day, you increase your risk of developing mild cognitive impairment (MCI), which often precedes Alzheimer's disease, said a study at the Mayo Clinic in Scottsdale, Ariz.

Dr. Yonas E. Geda and his colleagues studied 1,233 people ages 70 to 89 who were free of overt dementia. After testing their memory, language and sense of direction, the team concluded that 163 participants already had MCI. And they found that those 163 people had a higher caloric intake than those who tested normal, and the higher the caloric intake the higher the chances of having MCI. Geda doesn't don't know exactly what the connection is, but a growing body of research suggests that a calorie-rich diet may be hard on the brain.

FATAL OVERDOSES LINKED TO METHADONE

Methadone accounted for almost a third of the deaths caused by opioid pain relievers in 2009, even though it was prescribed far less often than other such drugs, researchers found.

Researchers writing in Morbidity and Mortality Weekly Report crunched data from the National Vital Statistics System and the Drug Enforcement Administration. The rate of overdose deaths involving methadone in 2009 was more than five times the rate in 1999. The drug accounted for 1.7 percent of the 257 million prescriptions written in 2009 for opioid pain relievers, but it was involved in 31.4 percent of overdose deaths. Methadone has a longer duration of action than other opioids, and it is inexpensive, which may help explain its increasing use. But it can accumulate in the body to toxic levels, leading to respiratory depression and heart rhythm problems.

DATABASE STARTED FOR FOOD BACTERIA

A new public database aims to catalog the genetic codes of 100,000 types of bacteria found in food, vastly increasing the amount of data that scientists can use to trace the causes of food-borne illness.

The free database, being set up at the University of California, Davis, will enable scientists to pinpoint not only what food carries the bacteria responsible for a given outbreak -- raw tuna in sushi, for example -- but also what country it came from. And while responses to such outbreaks have typically taken weeks, the database is expected to reduce that to days. "It's actually a big deal from a scientific standpoint," said Steven Musser of the Food and Drug Administration.

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