Epidemiology

Toxoplasma gondii occurs worldwide, with a higher prevalence in tropical areas and low- and middle-income countries.[1][6]

In many countries, prevalence has steadily decreased over the past several decades. In the US, the seroprevalence among people ages 12-49 years from 2011 to 2014 was 7.7%, a decrease from 10.1% in 2009 to 2010 and 16% in 1988 to 1994.[7][8]​ National surveys in France have shown a decreasing Toxoplasma seroprevalence among pregnant women, with models estimating a decrease in prevalence from 76% in 1980 to 27% in 2020.[9] The high seroprevalence in southern Europe is thought to be due to ingestion of undercooked meat and poor kitchen hygiene. Seroprevalence in South America is also high, ranging from 43% to 73%, affected by waterborne transmission and ingestion of undercooked meat.[10]

Seroprevalence is low in most Asian countries (1% in pregnant women in Korea, 10% in HIV-positive patients in Taiwan), although India (45%) and Malaysia (56%) have higher prevalence rates.[10]

Worldwide approximately 33% of pregnant women have latent toxoplasmosis.[6] ​Fewer than 1 in 1000 pregnant women acquire Toxoplasma during pregnancy, and the incidence of congenital toxoplasmosis in the US is approximately 0.23 cases per 10,000 live births.[11]​ There is an increased risk of mother-to-child transmission with increasing gestational age at seroconversion (15%, 44%, and 71% after acute primary infections at 13, 26, and 37 weeks of gestation, respectively). Appropriate treatment at the earliest opportunity reduces mother-to-child transmission and may also reduce symptomatic infection in the infant.[11]

To enhance the accuracy of toxoplasmosis reporting and enable more effective prevention and control strategies, development of standardized surveillance and case definitions is needed. Diagnosing toxoplasmosis can be challenging due to high rates of asymptomatic acute infection among immunocompetent individuals (including pregnant women), the risk of disease reactivation in immunocompromised patients, and the potential for congenital infections to manifest later in life.[12]​ The Centers for Disease Control and Prevention have published T gondii case definitions, which have the potential for use if toxoplasmosis becomes a nationally reportable condition in the US.[13]

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