ABSTRACT
Toxoplasmosis is due to the protozoan Toxoplasma gondii. The cat is the definitive host and humans are infected by ingesting environmental oocysts or infected foods. There is a circulating, replicative form called the tachyzoite and a more quiescent tissue dwelling form called the bradyzoite. Antibody with complement can kill tachyzoites, but cell-mediated immunity is required to kill intracellular stages. Infections are often asymptomatic, but serious consequences may follow congenital infection or may occur in the immunocompromised. Diagnosis is often based on serology. When treatment is indicated, pyrimethamine plus sulfadiazine is often used, in conjunction with folinic acid.
