Many scientists over the years have found an association between cat ownership as a child and chronic diseases as an adult. Scientific findings have been inconsistent, in part because the studies do not consider critical factors such as if and when toxoplasmosis was acquired by a child. The risk of toxoplasmosis transmission to humans is greatest shortly after the cat/kitten acquires toxoplasmosis; in feral cats; when litter boxes are used indoors; and when litter boxes are not cleaned daily. Kittens and cats shed large quantities of toxoplasmosis, in the first three weeks after acute infection; and after 24 hours, toxoplasmosis in a litter box can become airborne, contaminate the environment, and be inhaled by the cat owner. We discussed toxoplasmosis in our book in CHAPTER 6: THE INFECTIOUS CASCADE OF PARASITIC DISEASE, in more detail, with additional references:
Chronic toxoplasmosis can cause central nervous system disorders, focal nervous system disease, demyelinating disease, epilepsy, and movement disorders; and regressive developmental disorders in a fetus. Toxoplasmosis can cause mental illnesses, including schizophrenia, depression, anxiety, obsessive compulsive disorder, bipolar disorder, hostility, an increase in anger, emotional outbursts disproportionate to the circumstance, and reckless behavior, decades after exposure. Toxoplasmosis increases testosterone in male brains, and has been linked to outbursts of anger and aggression, reckless and dangerous behavior; and an increased risk of car accidents, self-harm, and self-mutilation. Toxoplasmosis can cause impulsive aggression and intermittent explosive disorder, a psychiatric disorder characterized by recurrent, impulsive, problematic outbursts of verbal or physical aggression that are disproportionate to the situations that trigger the outbursts. Toxoplasmosis has also been associated with Alzheimer’s disease, and brain cancer.
We once read children were being allowed to kiss feral kittens at a county fair—exposing children to a high risk of toxoplasmosis transmission that was beyond the reach of any study of children with household cats. Toxoplasmosis is an insidious chronic disease, which can cause significant physical and mental illness decades after the acute infection.