Radiolab is one of my favorite podcasts. It probes various scientific and philosophical questions in a very interesting way. Recently they did an episode on parasites. There was some fascinating stuff about hookworms that supported some of my own theories about the dangers of living in an overly sterile environment. There was also a segment on Toxoplasmosis.
Most people speak of toxoplasmosis in the context of pregnancy. Pregnant women are told to stay away from cat feces to avoid contracting toxoplasmosis so that the baby is not infected. Toxoplasmosis is caused by Toxoplasma gondii. Various types of animals can carry this infection but it can only breed inside of a cat.
If a mouse or rat contracts toxoplasmosis, the parasite will affect its brain so that the mouse becomes sexually attracted to cat urine. Being in close contact with cat urine results in being eaten by a cat. When the mouse is digested, the toxoplasma gondii finds fertile breeding ground in the belly of the cat. Some believe that toxoplasmosis may have a similar affect on some humans and might help explain the crazy cat lady, schizophrenia, and other neurological disorders. Studies have shown that infected people get in six times as many car accidents.
The producers of Radiolab have a Darwinian worldview. But a Darwinian explanation of the survivial of Toxoplasma gondii seems highly unlikely. It has to keep getting back inside of cats in order to breed and it does this by drugging the mouse into being sexually attracted to cat urine. An Intelligent Designer seems far more plausible than spontaneous mutation or gradual change over time resulting in a parasite that can do all this. If you don't get grossed out easily you should check out this video: