Leaders infected by a parasite

Toxoplasma gondii is an obligate intracellular parasitic protozoan that causes toxoplasmosis, which in humans is associated with a variety of neuropsychiatric and behavioral conditions. The parasite is capable of infecting virtually all warm-blooded animals,  but may undergo sexual reproduction only in felids (cats and its relatives). 

The parasite has been shown to increase rodents' chances of being preyed upon by felids by altering their behavior. As a consequence, rats that do not avoid cat habitations and are therefore more likely to become cat prey.

The famous Yellowstone National Park in Wyoming, USA, has a diverse carnivore community including gray wolves and cougars, intermediate and definitive hosts of the parasite, respectively. In a newly published investigation it was shown, that wolf territory overlap with areas of high cougar density was an important predictor of infection. 

In addition, wolves hosting the parasite were more likely to make high-risk decisions such as dispersing and becoming a pack leader, both factors critical to individual fitness and wolf vital rates. The change was considerable as the reported data showed that infected wolves were 11 times more likely than uninfected ones to leave their birth family to start a new pack, and 46 times more likely to become pack leaders - often the only wolves in the pack that breed.

The study did not provide data how this this behavioral modification of wolfs resulted in the parasite breeding in cougars, but according to the authors it is probable that the toxoplasmosis would create a feedback loop that increases spatial overlap and disease transmission between wolves and cougars. 

Taken together, the above described results show an example of unexpectedly complicated relationship between a parasite with its two hosts. The obvious question arising is the effect of toxoplasmosis on the behavior of humans. 

After all, it is very common. For example in the United States, approximately 11% of people have been infected, while in some areas of the world this is more than 60%. The infection rate in Finland is ca. 15%. 

Despite this, there is no scientific information about the parasite´s behavioral effect on infected humans. However, after reading the article linked above I would definitely be happy to see some research on the topic. 

Previous thoughts on the same topic:
Microbes manipulate their hosts (In Finnish, but can be read in English by Google translator)
World oceans are filled with previously unknown viruses
Seeing sex developed novel cultures