I think it's a lighthearted reference to studies which have demonstrated possible, albeit minor, psychological and physiological effects on humans after infection with the Toxoplasma gondii parasite [1].
In rodent models, infection appears to exert effects which make the rodent more likely to be killed and eaten by felines in order to complete the infection cycle of the parasite in the digestive tract of the feline.
The suggestion being that similar effects might be occurring in humans, particularly cat owners who are likely to be carriers of the parasite, manifesting in increased positive behaviours towards the cat.