What Is Toxoplasmosis?

Toxoplasmosis is an infection caused by a tiny parasite called Toxoplasma gondii. This one-celled parasite is most common in cats, but humans and other animals also can get infected.

Who Gets Toxoplasmosis?

Anyone can get toxoplasmosis (tok-so-plaz-MOE-sis). Experts think that millions of people in the United States are infected with T. gondii. But most have no symptoms because their immune systems are healthy and keep the parasite from causing harm.

Toxoplasmosis is most serious for:

  • Pregnant women, who may pass the infection to their babies. When a child is infected before birth, it is called congenital toxoplasmosis. 
  • People with weakened immune systems. This can include people with HIV/AIDS or cancer. It also includes people who take medicines that weaken the immune system, such as steroids or medicines taken after organ transplants.

What Are the Signs & Symptoms of Toxoplasmosis?

When someone gets toxoplasmosis, the parasite remains in the body for life. It's usually not a problem, though. In most cases, people don't even know they're infected because they don't have any symptoms.

When kids do have symptoms, they will vary depending on a child's age and how well their immune system works:

In otherwise healthy children, toxoplasmosis can look like the flu or mono. Symptoms can include:

Babies with congenital toxoplasmosis often don't have any symptoms at birth. But problems might show up months or years later. They can range from mild to severe:

  • vision problems and even blindness from injury to the retina (back of the eye)
  • brain damage leading to developmental delay, seizures, hearing loss, limp muscle tone, or an unusually large or small head
  • fever
  • swollen glands
  • jaundice (yellowed skin and eyes)
  • rash
  • problems with blood cells, such as anemia or thrombocytopenia
  • a large liver or spleen

The most severe cases of congenital toxoplasmosis happen when the mom is infected early in the pregnancy. This can lead to miscarriage or the baby might be born early or very small.

Kids with weakened immune systems can have all the symptoms listed above, as well as problems with their lungs and heart. Many of these kids also have inflammation in the brain (encephalitis).

How Does Toxoplasmosis Spread?

People can catch toxoplasmosis from:

  • eating raw or undercooked meat (especially lamb, pork, and venison) from infected animals, or drinking contaminated water or unpasteurized milk
  • handling cat feces (poop) or soil that contains T. gondii eggs
  • being born with it (a woman who gets toxoplasmosis while pregnant may pass the parasite to her unborn child through the bloodstream)
  • very rarely, a contaminated blood transfusion or organ transplant

How Is Toxoplasmosis Diagnosed?

To find out if someone has toxoplasmosis, doctors ask about exposure to household cats or contaminated food or water sources. They also might do tests to check for:

  • the T. Gondii parasite (or its DNA) in the blood or body tissues
  • antibodies to T. Gondii in the blood 
  • changes in the brain, eyes, ears, and other organs. Imaging studies such as ultrasound, CT or MRI can be helpful.

How Is Toxoplasmosis Treated?

Treatment for toxoplasmosis varies based on a child's age and general health. Otherwise healthy kids don't usually need medicine, since toxoplasmosis goes away on its own in a few weeks or months. Babies with congenital toxoplasmosis and kids with weakened immune systems will need to take anti-parasite medicine.

Can Toxoplasmosis Be Prevented?

To help prevent toxoplasmosis in your family:

  • Cook meats thoroughly to kill germs. Cook whole meat to at least 145ºF. There should be no pink areas and juices should be clear. Cook ground meat to at least 160ºF, and poultry to at least 165ºF.
  • Wash your hands with soap and water after handling raw meat or unwashed vegetables, or gardening outside.
  • Wash all fruits and vegetables before serving. You may also want to peel them.
  • Wash all utensils well with soap and warm water.
  • Don't drink untreated water or unpasteurized milk.
  • Teach children the importance of washing hands well and often to prevent infection.
  • Close outdoor sandboxes, especially overnight, to prevent wandering cats from using it as a litterbox.

If you have a cat:

  • Change its litterbox daily. T Gondii eggs aren't infectious until at least a day after a cat poops. If you are pregnant, have someone else change the litterbox daily.
  • Keep it indoors to prevent it from getting toxoplasmosis from the soil or from small infected animals it eats.
  • Don't feed it raw meat.

When Should I Call the Doctor?

Call your doctor if your child has symptoms of toxoplasmosis, especially if your child:

  • is being treated for AIDS or cancer
  • has a condition or takes medicine that weakens the immune system

If you're pregnant or trying to become pregnant, call your doctor right away if you notice even one swollen gland, especially if you've been around cats or ate raw or undercooked meat.

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.