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It is estimated that 500 million people worldwide are infected with Toxoplasma gondii.1 Seroprevalence studies have uniformly indicated increasing rates with age (eFig. 354.1). Between 1999 and 2004, the age-adjusted T. gondii seroprevalence rate declined from 14.1% to 9% among U.S.-born persons ages 12 to 49 years.2 The rates varied among regions, probably due to differing climates, culinary practices, and immigration patterns from areas of the world that have higher endemic rates of Toxoplasma infections. Data from Europe generally indicates a slightly higher prevalence rate compared to the United States, with rates in Central Europe ranging from 24% in Greece to 41% in France and Poland.3-5 In the United States, seroprevalence rates in women of childbearing age are approximately 15%, whereas rates in similar populations from western Europe, Africa, and Central and South America are greater than 50%.1,6 The general population of blood donors from Turkey was found to have a 20% seroprevalence rate, while the seroprevalence restricted to women was found to be relatively high at 52.1%.7,8 In the last two decades, most European countries have noted a decrease in seroprevalence of Toxoplasma, possibly due to less infection in farm animals, more filtration of drinking water, and concerns about consuming undercooked meat.

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eFigure 354.1.
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Prevalence of Toxoplasma antibody among US-born persons, by age and race/ethnicity. (From Jones JL, Kruszon-Moran D, Sanders-Lewis K, et al. Toxoplasma gondii infection in the United States, 1999 2004, decline from the prior decade. Am J Trop Med Hyg. 2007;77:405-10.)

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Seroprevalence rates in India, Sudan, Uganda, and Malaysia range from 20% to 55% in recent studies.9-12 In New Zealand, 33% of women who had antenatal blood work were found to have antibodies to T gondii, indicating past infection.13 Seroprevalence in Brazil was estimated to be between 40% to 80%.14 Globally, infection rates primarily reflect soil temperatures—infection is much more common in warmer or temperate climates and is much less common in colder climates, such as in the northern hemispheres. Specific populations at risk included butchers and individuals of lower socioeconomic status.15,16 A study of children in a low-socioeconomic community in Brazil found a seroprevalence rate of 32.4%.17

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T. gondii is a parasite for which the members of the feline species (ie, cats, kittens, cougars) are the definitive hosts.18 Felines ingest the cyst form that is present in soil, which germinates in the cat’s small intestine and produces oocysts. The oocysts are then excreted in the feces for a period of 7 to 20 days into the surrounding environment. The oocyst can sporulate and become infective in the proper environmental conditions (such as warm soil). The oocyst does not sporulate below 4°C, which explains why colder climates would be inhospitable to sporulation. It is the sporulated oocyst that is infective when ...

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