A protozoan parasite spread through food or water contaminated with oocysts, through infected meat or through contact with oocysts from feline feces.
Acute infection is usually asymptomatic, and once acquired, parasites remain in human tissues life-long.
Symptomatic disease can be seen in immunocompromised patients with reactivation of latent infection or with acquisition of new infection.
Symptomatic eye disease can be seen in both immunocompromised and immunocompetent patients.
Primary infection during pregnancy is often asymptomatic in the mother, but can result in congenital disease in the fetus.
Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii . Cats are the definitive hosts for the parasite, and can excrete millions of oocysts, which survive in the environment for months. Humans are intermediate hosts, and become infected by ingesting uncooked meat infected with tissue cysts (bradyzoites), by ingestion of other food or water contaminated with oocysts, or by transplacental spread of tachyzoites.  Once bradyzoites or oocysts are ingested, or tachyzoites have spread through the placenta to a fetus, T gondii rapidly travels to tissues and organs where it encysts and remains permanently. Infection in humans is life-long and often asymptomatic, unless a patient becomes immunosuppressed.
Department of Medicine
Division of Infectious Diseases and Immunology
New York University School of Medicine
SH declares that she has no competing interests.
Professor of Medicine (Infectious Diseases) and Microbiology and Immunology
Albert Einstein College of Medicine
KK is on the advisory board for the Sanford Guide for Antibiotic Therapy.
Professor of Parasitology
University of Pisa
School of Medicine
FB declares that he has no competing interests.
SN declares that he has no competing interests.
Professor of Medicine
University of Connecticut Health Center
GYW is on the medical advisory boards of the following: Gilead Sciences, Bristol-Myers Squibb, AbbVie, and Intercept.
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