A search for Toxoplasmosis on G-scholar reveals that this parasite is in fact a problem for immune compromised patients and infants. Although I do not think WebMD is a reliable source, another comment here cites them to indicate that infections are usually cleared up by our immune system. This appears to be plausible, but because the parasite enters cells, and can hide in a latent phase, your immune system may be unable to clear the infection permanently. Because the parasite can halt the cell cycle, it may be able to hide indefinitely. I would not be concerned about a latent parasite, but its re-emergence may become a problem if your immune system becomes compromised.

A correction to your statement that, according to wikipedia, the disease cannot be tested by blood sample. Wikipedia, in fact, stats that it can be tested by blood or other tissue, but only if the parasite is active (non-latent).

Regarding its effect on behavior, the parasite seems to increase dopamine levels and possibly inhibit fear response. Since the increased dopamine is caused by an enzyme made by the parasite, this probably only occurs during a full scale infection. The inhibition of fear may occur while the parasite is inactive, if the parasite is able to enter cells in your amygdala. I do not see this inhibition of fear as long-lasting, except perhaps in extreme cases.

One disclaimer, I grew up with a few cats, so I may have been, or am currently, infected. I cannot rule out that this parasite is manipulating me to write this comment. Now I'm off to find some cat pee. Can't get enough of that smell, mmmmmmmm.....

More technical wiki article: https://en.wikipedia.org/wiki/Toxoplasma_gondii