Toxoplamosis & Its Effects

Toxoplasmosis is a disease caused by a parasitic protozoan Toxoplasma gondii (shown above). Cats are the defintive host  but it can also infect humans and other warm blooded animals. It is acquired from contact with cats and their feces or by eating raw meat. When people are infected they are often not aware of it, but typical symptoms are swollen lymph nodes and muscle aches including pain. A healthy immune system usually prevents a second infection. But it can cause severe problems mostly to people who have a weak immune system due to e.g. chemotherapy or HIV/AIDS. Symptoms can be damaging to the eyes, brain or other organs. 

The effects of toxoplasmosis are very interesting. For instance, when a rat's brain gets infected (usually because the rat came in to touch with cat poop) it manipulates its behaviour. The rat does not flee anymore when it smells the urine of a cat because this increases activity in the brain associated with sexual attraction. The rats develop a “love” for cats and due to the loss of fear they are more frequently eaten by cats. 

Another unusual effect is outlined by S. Kankova and her team from the Department of Parasitology, Czech Republic. They discovered that infected women are more likely to give birth to boys than to girls. They tested about 1800 women in private clinics including their age, the concentration of anti-toxoplasm antibodies and the sex of the newborn. The result was that for about every 260 boys, 100 girls were born. Researchers explained the fact that male embryos rather survive due to toxoplasmosis modulating and suppressing effects on the immune system which are different depending on the sex of the embryo. 

It has also been shown that toxoplasmosis infects enzymes in the brain which then cause neurobehavioral symptoms that arise after infection. Those can be e.g. slower reactions. Studies have shown that many car accidents happened and people died all over the world because the people involved were infected with toxoplasmosis but did not know about that. Other studies showed that the brain damage due to toxoplasmosis may have an impact on the person´s personality and characteristics. The researcher Nicky Boulter from the Sydney University of Technology found out that the changes depend on the sex of the person. Men on the one hand become more independent, anti-social, jealous etc. and women on the other hand become friendlier, more outgoing, seem more attractive to men and some studies showed that their level of intelligence increases. 

Toxoplasmosis can be diagnosed by using blood checks for the presence of Toxoplasma gondii. Treatment  is generally not required, except in the case of pregnant women or immuno-suppressed individuals. If a pregnant woman is infected this can have serious impact. There are antibiotics which can be used before the child is infected which prevent its infection in most cases but those also have other risks for the mother. 

Written by Junior Frog Blog Reporter Marie von Brauchitsch. Submitted for the St. Columba's College Biology Prize 2012.