Scientists have discovered infections that alter the behavior in plants, humans and other mammals. In the past, findings from the tomato plant concluded the majority of microbe behavior research. In the example of a tomato plant, a virus relies on a certain insect called a thrip, which jumps from plant to plant, sticking it’s oral probe into the plant’s cells to spread the virus. The virus itself manipulates the insect to get to the next plant. Once the thrip consumes the virus, its behavior changes because it spends more time feeding and licking plant cells, coating each tomato cell with the virus in the process.
The deadly Hantavirus, which is a distant strand of the same tomato plant virus, caused infected rats to become more aggressive. Rabies has caused mammals to go crazy and be unable to swallow; a rabid animal is more likely to bite and spread the saliva-transmitted Rabies. Most viruses have subtle effects and could be difficult to determine whether or not a person’s behavior is a result of the virus itself. An example of this would be the Cold virus, which is said to make people friendlier right before symptoms appear and when they’re the most contagious. The virus needs this to survive, because the host will spread the illness.
The parasite that causes toxoplasmosis is the most serious of the behavior-changing microbes. This parasite can live in cats, rodents, livestock, and other warm-blooded animals, but it reproduces only inside the feline intestinal tract and is carried by feline feces or contaminated soil. Research has shown several personality traits that appear to be associated with toxoplasmosis. Men are willing to disregard social norms and can become more jealous. Women tend to be more friendly, easygoing, and attentive to others. When infected, both genders tend to be more insecure. Those infected with toxoplasmosis also have slower reaction times and more people that have been infected have been reported to have more car accidents.