Needless to say, I disagree most vehemently. However, there is a point that is worth elaborating:
There is a parasitic protozoan, Toxoplasma gondii, which is related to the one causing Malaria. Like many parasites, it has a complex life cycle involving a definitive host, in which it takes its final form and reproduces (sexually) and an immediate host in which it undergoes into the form that infects the final host. Also, like many parasites, it causes changes in said immediate hosts that make them more likely to be consumed by the final host. The final hosts of Toxoplasma are felids, with most other warm-blooded animals being immediate hosts, where it causes a reduction in risk aversion. In rodents, infection causes a loss of the instinctual fear of cats, and indeed sexual stimulation from the stench of cat urine. It is generally harmless to humans - indeed, half of the species is infected assymptomatically -, but it can cause neurological problems in immunocompromised individuals and birth defects when infection occurs during pregnancy, which why pregnant and immunocompromised people should not eat undercooked meat (well, yet another reason) and avoid interacting with cat feces, and it has links to schizophrenia and anxiety disorders.
It is not symbiosis, it is parasitism. In mature cats, it is generally subclinical, and they generally develop immunity once they’ve gone through it (there is research on developing a vaccine, but so far unsuccessful)), but various complications are possible and can be fatal in kittens.
