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Toxoplasmosis in HIV-infected patients

Rajesh T Gandhi, MD
Section Editor
John G Bartlett, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Toxoplasmosis is the most common central nervous system infection in patients with the acquired immunodeficiency syndrome (AIDS) who are not receiving appropriate prophylaxis [1,2]. This infection has a worldwide distribution and is caused by the intracellular protozoan parasite, Toxoplasma gondii. Immunocompetent persons with primary toxoplasmosis are usually asymptomatic, and latent infection can persist for the life of the host. In immunosuppressed patients, especially patients with AIDS, the parasite can reactivate and cause disease, usually when the CD4 count falls below 100 cells/microL [1,3,4].

This topic will focus on the clinical manifestations, diagnosis, and treatment of toxoplasmosis in HIV-infected patients. A discussion of toxoplasmosis in immunocompetent hosts is found elsewhere. (See "Toxoplasmosis in immunocompetent hosts".)


The probability of developing reactivated toxoplasmosis is as high as 30 percent among AIDS patients with a CD4 count <100 cells/microL who are toxoplasma seropositive and are not receiving effective prophylaxis or antiretroviral therapy [5-8]. The most common site of reactivation is the central nervous system (CNS).

Transmission — In humans, toxoplasmosis is typically acquired through ingestion of infectious oocysts, usually from soil or cat litter contaminated with feline feces, or undercooked meat from an infected animal. When humans ingest T. gondii oocysts, the organisms invade the intestinal epithelium and disseminate throughout the body. They then encyst in any type of nucleated cell and can lie dormant within tissues for the life of the host. A more detailed discussion on the transmission of toxoplasmosis is found elsewhere. (See "Toxoplasmosis in immunocompetent hosts".)

Prevalence of infection — The prevalence of infection with T. gondii varies substantially among different countries and ranges from approximately 11 percent in the United States to more than 80 percent in certain European, Latin American, and African countries [9]. In general, the seroprevalence of antibodies to T. gondii among HIV-infected patients mirrors the rate of seropositivity in the general population and is not related to owning a cat [10,11]. However, the prevalence may be associated with age. As an example, in a study of HIV-infected women in the United States, those who were ≥50 years old were more likely to be seropositive compared with younger women (odds ratio 2.4, 95% CI 1.4 to 3.9) [10].

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Literature review current through: Nov 2017. | This topic last updated: Jul 21, 2016.
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