Toxoplasmosis

Toxoplasmosis is an illness caused by an infection with the parasite Toxoplasma gondii (T. gondii). The parasite reproduces in the intestinal tracts of cats. Humans become infected by direct or indirect contact with cat poop (feces) or by eating undercooked meat.

Most people don’t have symptoms when they get infected. But as your immune system attacks the parasite, it creates cysts in your body. The parasite can live inactive (dormant) in these cysts and make you sick when it reactivates at a later time.

Who does toxoplasmosis affect?

While T. gondii can infect anyone, most people won’t have symptoms. Your body usually fights off the parasite without you knowing it was there. Toxoplasmosis is most dangerous in pregnancy and for those with weakened immune systems, like people living with HIV or cancer.

While T. gondii needs cats to reproduce, cat ownership itself doesn’t seem to increase your risk of infection significantly.

Toxoplasmosis in pregnancy

If you get toxoplasmosis during pregnancy or shortly before getting pregnant, you can pass the parasite through the placenta to the fetus. This increases the risk of miscarriage, stillbirth or serious health problems for your future child. Complications of being born with toxoplasmosis include vision problems, blindness, developmental delays and learning differences.

Toxoplasmosis when you’re immunocompromised

If you’re living with HIV or cancer or if you’re taking immune-suppressing medications, your immune system can’t fight off infections like T. gondii. This means you have a compromised immune system (immunocompromised).

While most people can fight off toxoplasmosis without symptoms, a new or reactivated infection can cause life-threatening complications in someone with a weakened immune system.

If you’ve had toxoplasmosis in the past, T. gondii lives in cysts in your body. When your immune system is weakened, it can reactivate and cause you to get sick.

Left untreated, toxoplasmosis can cause organ damage in someone with a compromised immune system. This can eventually lead to death.

How common is toxoplasmosis?

Worldwide, it’s estimated that up to 1 in 3 people are infected with (T. gondii), the parasite that causes toxoplasmosis. Most people who are infected don’t have any symptoms.