Featured Research

from universities, journals, and other organizations

Toxoplasma infection permanently shifts balance in cat and mouse game

Date:
September 18, 2013
Source:
University of California - Berkeley
Summary:
Infection with the toxoplasma parasite makes mice fearless in the presence of cats -- to their regret. But how does the protozoan do that? Scientists looked at the effects of three common strains of toxoplasma and found that they remove the fear of cat urine for as long as four months, long after the mice have cleared the parasite from their brains. The parasite appears to make permanent changes in the brain's neurons.

Researchers found that mice's lack of fear of cats persisted even when inflammation markers or cysts could not be detected in mice.
Credit: Wendy Ingram and Adrienne Greene

The Toxoplasma parasite can be deadly, causing spontaneous abortion in pregnant women or killing immune-compromised patients, but it has even stranger effects in mice.

Related Articles


Infected mice lose their fear of cats, which is good for both cats and the parasite, because the cat gets an easy meal and the parasite gets into the cat's intestinal track, the only place it can sexually reproduce and continue its cycle of infection.

New research by graduate student Wendy Ingram at the University of California, Berkeley, reveals a scary twist to this scenario: the parasite's effect seem to be permanent. The fearless behavior in mice persists long after the mouse recovers from the flu-like symptoms of toxoplasmosis, and for months after the parasitic infection is cleared from the body, according to research published today (Sept. 18) in the journal PLOS ONE.

"Even when the parasite is cleared and it's no longer in the brains of the animals, some kind of permanent long-term behavior change has occurred, even though we don't know what the actual mechanism is," Ingram said. She speculated that the parasite could damage the smell center of the brain so that the odor of cat urine can't be detected. The parasite could also directly alter neurons involved in memory and learning, or it could trigger a damaging host response, as in many human autoimmune diseases.

Ingram became interested in the protozoan parasite, Toxoplasma gondii, after reading about its behavior-altering effects in mice and rats and possible implications for its common host, the domesticated cat, and even humans. One-third of people around the world have been infected with Toxoplasma and probably have dormant cysts in their brains. Kept in check by the body's immune system, these cysts sometimes revive in immune-compromised people, leading to death, and some preliminary studies suggest that chronic infection may be linked to schizophrenia or suicidal behavior.

Pregnant women are already warned to steer clear of kitty litter, since the parasite is passed through cat feces and can cause blindness or death in the fetus. One main source of spread is undercooked pork, Ingram said.

With the help of Michael Eisen and Ellen Robey, UC Berkeley professors of molecular and cell biology, Ingram set out three years ago to discover how Toxoplasma affects mice's hard-wired fear of cats. She tested mice by seeing whether they avoided bobcat urine, which is normal behavior, versus rabbit urine, to which mice don't react. While earlier studies showed that mice lose their fear of bobcat urine for a few weeks after infection, Ingram showed that the three most common strains of Toxoplasma gondii make mice less fearful of cats for at least four months.

Using a genetically altered strain of Toxoplasma that is not able to form cysts and thus is unable to cause chronic infections in the brain, she demonstrated that the effect persisted for four months even after the mice completely cleared the microbe from their bodies. She is now looking at how the mouse immune system attacks the parasite to see whether the host's response to the infection is the culprit.

"This would seem to refute -- or at least make less likely -- models in which the behavior effects are the result of direct physical action of parasites on specific parts of the brain," Eisen wrote in a blog post about the research.

"The idea that this parasite knows more about our brains than we do, and has the ability to exert desired change in complicated rodent behavior, is absolutely fascinating," Ingram said. "Toxoplasma has done a phenomenal job of figuring out mammalian brains in order to enhance its transmission through a complicated life cycle."


Story Source:

The above story is based on materials provided by University of California - Berkeley. Note: Materials may be edited for content and length.


Journal Reference:

  1. Wendy Marie Ingram, Leeanne M. Goodrich, Ellen A. Robey, Michael B. Eisen. Mice Infected with Low-Virulence Strains of Toxoplasma gondii Lose Their Innate Aversion to Cat Urine, Even after Extensive Parasite Clearance. PLoS ONE, 2013; 8 (9): e75246 DOI: 10.1371/journal.pone.0075246

Cite This Page:

University of California - Berkeley. "Toxoplasma infection permanently shifts balance in cat and mouse game." ScienceDaily. ScienceDaily, 18 September 2013. <www.sciencedaily.com/releases/2013/09/130918181110.htm>.
University of California - Berkeley. (2013, September 18). Toxoplasma infection permanently shifts balance in cat and mouse game. ScienceDaily. Retrieved October 31, 2014 from www.sciencedaily.com/releases/2013/09/130918181110.htm
University of California - Berkeley. "Toxoplasma infection permanently shifts balance in cat and mouse game." ScienceDaily. www.sciencedaily.com/releases/2013/09/130918181110.htm (accessed October 31, 2014).

Share This



More Plants & Animals News

Friday, October 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How A Chorus Led Scientists To A New Frog Species

How A Chorus Led Scientists To A New Frog Species

Newsy (Oct. 30, 2014) A frog noticed by a conservationist on New York's Staten Island has been confirmed as a new species after extensive study and genetic testing. Video provided by Newsy
Powered by NewsLook.com
Surfer Accidentally Stands on Shark, Gets Bitten

Surfer Accidentally Stands on Shark, Gets Bitten

AP (Oct. 30, 2014) A 20-year-old competition surfer said on Thursday he accidentally stepped on a shark's head before it bit him off the Australian east coast. (Oct. 30) Video provided by AP
Powered by NewsLook.com
Ebola Inflicts Heavy Toll on Guinean Potato Trade

Ebola Inflicts Heavy Toll on Guinean Potato Trade

AFP (Oct. 30, 2014) The Ebola epidemic has seen Senegal and Guinea Bissau close its borders with Guinea and the economic consequences have started to be felt, especially in Fouta Djallon, where the renowned potato industry has been hit hard. Duration: 02:01 Video provided by AFP
Powered by NewsLook.com
Genetically Altered Glowing Flower on Display in Tokyo

Genetically Altered Glowing Flower on Display in Tokyo

Reuters - Innovations Video Online (Oct. 30, 2014) Just in time for Halloween, a glowing flower goes on display in Tokyo. Instead of sorcery and magic, its creators used science to genetically modify the flower, adding a naturally fluorescent plankton protein to its genetic mix. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins