It sounds like science fiction, alright

According to a study by Kevin Lafferty,

"The geographic variation in the latent prevalence of Toxoplasma gondii may explain a substantial proportion of human population differences we see in cultural aspects that relate to ego, money, material possessions, work, and rules."

Although this sounds like science fiction, it is a logical outcome of how natural selection leads to effective strategies for parasites to get from host to host, said Lafferty. Toxoplasma gondii is a parasite of cats, both domestic and wild. Although modern humans are a dead-end host for the parasite, Toxoplasma appears to manipulate human personality by the same adaptations that normally help it complete its life cycle. The typical journey of the parasite involves a cat and its prey, starting as eggs shed in an infected cat's feces, inadvertently eaten by a warm-blooded animal, such as a rat. The infected rat's behavior alters so that it becomes more active, less cautious, and more likely to be eaten by a cat, where the parasite completes its life cycle. Many other warm-blooded vertebrates may be infected by this pathogen, including marine mammals: a study begun in 2001 discovered that Toxoplasma gondii had caused 8 percent of stranded-sea-otter deaths in California between 1967 and 1989, the sea otters likely acquiring the parasite from cat feces that had been washed to sea (see Sound Waves article, Parasites as Indicators of Coastal-Ecosystem Health). In humans, the parasite commonly causes mild flu-like symptoms, after which it tends to remain in a dormant state in the brain and other tissues.

Evidence for subtle long-term effects on an individual's personality reported by researchers in the Czech Republic inspired Lafferty to explore whether a shift in the average, or aggregate, personality of a population might occur where Toxoplasma has infected a higher proportion of individuals. Infection with Toxoplasma varies considerably from one population to another; in some countries it is very rare, while in others nearly all adults are infected. To test his hypothesis, Lafferty used published data on cultural dimension and aggregate personality for countries where there were also published data on the prevalence of Toxoplasma antibodies in women of childbearing age. ...

The results of previous work suggested that Toxoplasma could affect specific elements of human culture. Toxoplasma is associated with different, often opposite behavioral changes in men and women, but both genders exhibit guilt proneness (a form of neuroticism). Lafferty's analysis found that countries with high Toxoplasma prevalence had a higher aggregate neuroticism score, and Western nations with high prevalence also scored higher in the "neurotic" cultural dimensions of "masculine" sex roles and uncertainty avoidance.

But what are the differences? According to Induction of changes in human behaviour by the parasitic protozoan Toxoplasma gondii, (using Contributions and Limitations of Cattell's Sixteen Personality Factor Model to parse the jargon) for men "low superego strength" (expedient, nonconforming, disregards rules, self indulgent), "protension" (vigilant, suspicious, skeptical, distrustful, oppositional), "guilt proneness" (apprehensive, self doubting, worried, guilt prone, insecure, worrying, self blaming ), and "group dependency" (group-oriented, affiliative, a joiner and follower dependent) were positively influenced in infected subjects. For women the prevailing factors were "affectothymia" (warm, outgoing, attentive to others, kindly, easy going, participating, likes people), "alaxia" (trusting, unsuspecting, accepting, unconditional, easy), and "self-sufficiency" (self-reliant, solitary, resourceful, individualistic, self sufficient).

So, not only can having a cat affect one's personality, but it affects men & women differently.

• The men become less trusting and the women more so.
  
• The men became more group dependent but the women less so.

So there is something behind the stereotype of the crazy cat lady.

Or

Infected men, suggests one new study, tend to become more aggressive, scruffy, antisocial and are less attractive. Women, on the other hand, appear to exhibit the “sex kitten” effect, becoming less trustworthy, more desirable, fun- loving and possibly more promiscuous.