Toxoplasmosis is an infection caused by the parasitic protozoan Toxoplasma gondii. This parasite can infect most warm-blooded animals, including humans, with domestic cats and their relatives as the definitive hosts shedding infectious oocysts in their feces. Humans usually become infected by eating undercooked or raw meat containing tissue cysts, contact with contaminated cat feces or soil, or congenitally from mother to fetus. Most infected people remain asymptomatic or have mild flu-like symptoms such as muscle aches and tender lymph nodes. However, severe disease can occur in people with weakened immune systems or in unborn babies when a woman is infected during pregnancy. Toxoplasmosis can affect the brain, eyes, and other organs. The parasite forms tissue cysts that remain dormant but can reactivate in immunocompromised people, causing serious disease. Diagnosis is typically made by blood antibody testing or molecular methods like PCR. Prevention includes cooking meat properly, avoiding contact with cat litter during pregnancy, and good hygiene. Treatment is often unnecessary for healthy individuals but may include medications like spiramycin or pyrimethamine/sulfadiazine with folinic acid during pregnancy or for severe cases. Up to one-third of the global population may be infected, but most do not show symptoms. Congenital toxoplasmosis causes about 200,000 cases annually worldwide. The infection has been linked to various neuropsychiatric and behavioral conditions, though such associations are still under study.
