T. gondii has been found worldwide in many species, including carnivorous and herbivorous mammals and birds. It has also been found in every population group of humans investigated. However, the definitive host was shown to be cats, which have been associated with transmission of the parasite in every population investigated. In the United States, most infection occurs through ingestion of contaminated meat, especially pork and lamb. One survey of pigs in the US found a seroprevalence of 42% in breeder pigs and 23% in market pigs. Another study in the 1960s found T. gondii in 32% of pork chops and 4% of lamb chops in grocery stores. In humans the seroprevalence is 22.5% at the national level, according a study of 17,658 people from 1988 to 1994. Because there is the extra concern of congenital infection in mothers, additional attention given to the prevalence in women of child-bearing age. The seroprevalence in the group of 15 to 44 year old women was reported to be 15%.
John and Petri.
Mandell, Bennett and Dolin.