A study released by Cornell back in 2011 showed link in behavior between infection of toxoplasmosis and behavior alterations. While a study released by the University of Prague showed that it can alter testosterone levels, and make males appear more dominant. It can even alter sexual behaviors. This is first of its kind for a pathogen. But can we blame the behaviors strictly on the toxoplasmosis? Or is the reality is a little more complex? Even the best of us could not hope to lay the burden right here.
The study actually concluded that in mice their behavior became erratic. They would actually look to be eaten by cats. The same way ants behave once they become infected with the mind controlling fungus which forces them to march up to a branch or leaf on the tree where it will grow out of their brain, killing them, before releasing spores. The toxoplasmosis behaves the same way. It forces the infected mice to commit risky behaviors. Ones which will benefit the pathogen. So it can continue the cycle, since cats are a vital part of the stages toxoplasmosis moves through.
It is by cat feces, raw meats or poorly cooked ones, and contaminated sources that humans get the pathogen, and over a quarter of all people are infected. Though some people are just carriers, because their immune system keeps the pathogen under control. It is not something doctors routinely look for unless you are a pregnant women. Because exposure to a cat litter box may be the source of infection.
The cycle of toxoplasmosis is quite diverse. Rodents and birds begin the cycle by becoming infected, they then pass it off to cats, who are highly infected, and from there the feces is usually deposited outside where animals like sheep and pigs come in contact with fecal matter and complete the cycle. Then humans eat the contaminated meat where the toxoplasmosis is contained, and become infected with the pathogen.
Most people who are infected will never clear the pathogen, just keep it under control with the immune system. In a person who is immune compromised though, the effects can take hold. Signs of fever, confusion, blurred vision can occur. Most people who are infected, though will never know without screening for the pathogen done by serology, and it is not spread by normal human contact. Which makes our mode of infection either contact with cat feces, or meat.
While the toxoplasmosis may cause behaviors in rodents, studies don’t show the same in humans. The reason for the behavior in rodents is due to the need to continue the cycle. While humans respond by having immune responses, it is enough to not kill the toxoplasmosis, but keep it at bay. So it can hide in our system but never be fully killed. Yet, in humans the pathogen does not need to manipulate control. While rodent brains are very similar to humans in chemistry, we are not identical. Neither is our position on the food chain. If toxoplasmosis was not able to cause erratic behavior in rodents then it could not continue the cycle. This might cause death of the pathogen. While humans make nothing more than constant hosts.
Humans my behave somewhat differently when under the full infection of toxoplasmosis, but only when it can become full blown. Otherwise the immune system is constantly keeping it in check, which means it is less likely to assert control. Mice however do become fully infected, that is because our immune system and brains are much more potent than theirs, and while we can be effected and infected the potential to rodents is much greater. Possibly because infection in rodents has existed for such a long time, and the pathogen has evolved to produce signals which can manipulate their brains.
The result for rodents is possibly deadly since they will purposely run in front of cats, and get themselves eaten. Toxoplasmosis does not just affect cats, and rodents, but all worm blooded species. Cattle, and horses as well as dogs can be come infected. The signs of their infection often show, because of the immune response, and even immune compromised animals will show signs of full blown toxoplasmosis. At that point humans have to use caution as well since the pathogen is producing ocysts and some of those can be expelled in feces and other bodily fluids, such as blood.
As for the change in sexual behavior in humans, as always the little guy gets the blame, but really can’t be. At best the pathogen might cause an abnormal decision, leading to an act. But seeing as how many parts of the brain are used for decision making it would be highly unlikely to be the direct cause of altered behavior in humans. Rodents have similar brain chemistry, but not function. So while behaviors are easily manipulated in them, humans actually have the ability to rationalize, and decision make. While rodents are bound by primitive skills, such as behavior patterns. They do not have the skills to rationalize decisions. So it would be far easier to manipulate the brain of a pattern seeking organism, over one who can do the secondary rationalizing.
What they can conclude, is that a woman will more likely have a son if infected with toxoplasmosis and while testosterone levels may rise and fall, it is the appearance of dominance that changes. Testosterone can make male features more masculine, change eating habits and growth. Though it can not be confirmed as a result fully based on toxoplasmosis. In fact it would be a jump. While toxoplasmosis can invade and disrupt normal function it does not have a determinate power over it. That is concluded by spikes and drops in testosterone based on environment and subtle changes. So while this may influence some males to mate more, or more often, it is not the whole process that mating goes through. Advantage can be taken by the pathogen, but only of pre-existing desire. No study has concluded that every male infected with this will go for every woman. In fact no study could conclude that since male behavior is based on many more factors. While this can be factored into a behavior pattern, it can not be credited for all the changes.
Looking at the behavior of the pathogen one can see that it is looking for hosts and consistent existence, while not doing it consciously. The blood borne pathogen has adapted to all environments being able to elude the immune system, and is capable of damaging people who are weak and sick. Also the pregnant should be highly aware of the dangers in changing litter boxes. While most of the effects of toxoplasmosis on humans are benign some of them can be fatal when HIV infections are present. If toxoplasmosis was ever linked to heightened sexuality causing exposure to HIV then it would be extremely dangerous, but like most other things in nature it can cause effects, but not directly intended effects. Much like the and and the fungus. It wants to spread and the ant is constantly in the environment where it spreads, so they are likely to return to where they contracted the fungus, or naturally move around. It is probably secondary signals such as changes in pressure, temp or other cell signals which cause the final growth stage of the fungus which kills the ant. That is the way with toxoplasmosis. Certain signals which already exist are amplified or used or shut off. While that seems like a power control, it is nothing more than an evolutionary development. With humans since sexual behaviors as well as others are located in many areas, it would have to send all the right signals or manipulate all the right hormones. Something that even the best of pathogens might never be able to do.
While we should all be aware of the presence of toxoplasmosis in our environment. We can help prevent the infection and spread of the disease. Women should avoid litter boxes while pregnant. Take caution to wash your hands after handling cats, or their feces. Make sure your meat is clean and cooked properly, and holds up to governmental standards. Use caution when cleaning in the kitchen. Most of all if you have the symptoms of toxoplasmosis you should ask your doctor for a test to confirm it. There is treatment available.