The manipulation hypothesis states a parasite may alter host behaviour for its own benefit, often by enhancing its transmission rate through the food chain. This paper reviews studies on the potential impact of one parasite, Toxoplasma gondii, on host behaviour, both on rodents, where altered responses may be proposed to benefit the parasite, and humans, where altered responses may arise as a side-effect of infection with no current adaptive significance.
I think that whilst, “cats no longer eat humans” – tigers and lions are still cats. Domestication would both help the parasite, lead humans to be less afraid of cats. Also, whilst from the point of view of the parasite, infection of humans have no obvious evolutionary benefit to the parasite – it would in the context of domestication – it increases the chance of the cat surviving.
A side effect of this would be the phenomena of cats on the internet.