Toxoplasmosis is an infectious disease found worldwide, caused by the single-celled parasite Toxoplasma gondii. In humans, infection poses a particular risk to pregnant women, as it can lead to birth defects. Like the closely related malaria pathogen—Plasmodium falciparum—and other related species, T. gondii possesses special organelles, so-called rhoptries and micronemes, for infecting the host cell.