Toxoplasmosis

Toxoplasmosis is a protozoan parasite that spreads through food or water contaminated with oocysts, infected meat, or contact with oocysts from feline feces.

Acute infection is usually asymptomatic, and once acquired, parasites remain in human tissues lifelong.

Symptomatic disease can be seen in patients who are immunocompromised with reactivation of latent infection or with acquisition of new infection.

Symptomatic eye disease can be seen in both patients who are immunocompromised and patients who are immunocompetent.

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 that 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.[1]Dubey JP. The life cycle of Toxoplasma gondii. In: Ajioka JW, Soldati D, eds. Toxoplasma molecular and cellular biology. Norfolk, UK: Horizon Bioscience; 2007:chapter 1. 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 lifelong and often asymptomatic, unless a patient becomes immunosuppressed.