T. gondii antibodies have been found worldwide (Table 3.1). The seropositivity increases with the age of the cat, indicating postnatal transmission of T. gondii.7,302 Antibodies to T. gondii have been detected in most cats after weaning (6 to 10 weeks). It is possible that in some young cats in Table 3.1, the low antibody titers represented maternally transferred antibodies. Maternally transferred antibodies disappear in the cat by 12 weeks of age.275,345,1008

Prevalence of T. gondii infection varies according to the life style of cats. It is generally higher in feral cats that hunt for their food than in domestic cats. Much is dependent on availability of food.244 Seroprevalence to T. gondii varied among countries, within different areas of a country, and within the same city (Table 3.1). The reasons for these variations are many, and no generalizations should be made. For example, low seroprevalence (7.3-11%) in Bangkok, Thailand, was attributed to the life style of the cats surveyed. Most (95%) people in Thailand are Buddhist, and killing any pet (or any life) is sinful. There are approximately 15,000 cats (30 × 500 temples) that live permanently around Buddhist temples, and these cats are fed by the public or monks, mainly a diet of cooked sh and rice.1245a

In a study of T. gondii seroprevalence in an urban population of domestic cats in Lyon, France,7 the seroprevalence was only 18.6% of 301 cats, approximately half the prevalence in other surveys in Europe (see Table 3.1). Prevalence was the highest when the weather was hot (>32°C) and moist (rain > 22 mm), or moderate and drier (rain 20 mm). Rarity of rodents in the area (due to regular rodent poison control) and feeding of cats by people were considered as possible factors for this reduced prevalence.