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Toxoplasmosis in Newborns

(Congenital Toxoplasmosis)


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Jul 2020| Content last modified Jul 2020
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Toxoplasmosis is infection with the parasite Toxoplasma gondii. It usually does not cause problems in healthy adults, but it can cause serious illness in newborns and in people with a weakened immune system.

  • Toxoplasmosis is caused by a parasite that lives and multiplies in cats.

  • A fetus may be born prematurely, and a newborn may have problems such as a small head or an enlarged liver.

  • Blood tests and tests of other fluids can be done to detect the infection in the fetus, newborn, or mother.

  • The infection may cause death in some children and long-term neurologic problems in others.

  • Pregnant women should avoid cat litter and should thoroughly cook meat before eating it.

  • Antiparasitic drugs may be given to fetuses or newborns to treat the infection.

The Toxoplasma gondii parasite lives and multiplies mainly in cats, and its eggs are shed in cat feces. Cat feces can contaminate food, soil, and water. Pregnant women become infected if they swallow Toxoplasma eggs after they touch contaminated cat litter, soil, or other objects and then touch their mouth or handle and eat food without washing their hands. Pregnant women can also become infected if they consume raw or undercooked meat or other foods that are contaminated. Fetuses become infected if Toxoplasma gondii crosses the placenta (the organ that provides nourishment to the fetus) during pregnancy.

Women who were infected before pregnancy typically do not pass the parasite on to their fetus unless their immune system has been weakened (for example, by HIV infection), reactivating the infection.

Infection in the fetus is more severe if the fetus is infected earlier in pregnancy.

Life Cycle of Toxoplasma gondii

  • 1a. Eggs are passed in cat stool. Many eggs are passed but usually for only 1 to 2 weeks. After 1 to 5 days in the environment, eggs become able to cause infection.

  • 1b. Cats can become reinfected by consuming food or other materials contaminated with the eggs.

  • 2. Other animals (such as wild birds, rodents, deer, pigs, and sheep) may consume the eggs in contaminated soil, water, plant material, or cat litter.

  • 3. Shortly after the eggs are consumed, they release forms of the parasite that can move (called tachyzoites).

  • 4. Tachyzoites spread throughout the animal's body and form cysts in nerve and muscle tissue.

  • 5. Cats become infected after eating animals that contain these cysts.

  • 6a. People can become infected by eating undercooked meat containing these cysts.

  • 6b. People can also become infected if they eat food, water, or other materials (such as soil) contaminated with cat stool or when they touch a pet cat's litter and then touch their mouth.

  • 7. Rarely, people are infected when they have a blood transfusion or organ transplant that contains the parasite.

  • 8. Rarely, the infection is spread from mother to fetus.

  • 9. In people, parasites form cysts in tissues, usually in muscle and the heart, brain, and eyes.

Life Cycle of  <i >Toxoplasma gondii</i>


The fetus may grow slowly and be born prematurely.

At birth, newborns usually do not have symptoms, but they may have a number of problems, including

  • Small head (microcephaly)

  • Brain inflammation

  • Jaundice (a yellow color of the skin or eyes)

  • Enlarged liver and spleen

  • Inflammation of the heart, lungs, or eyes

  • Rash

Inflammation of the eyes (chorioretinitis) can result in blindness. Severe neurologic problems, including seizures, may occur. Some children have intellectual disability.

Children born with congenital toxoplasmosis may be severely ill and die shortly after birth, or they may have no symptoms until months or years later. Some never become ill.


  • For the mother: Blood tests

  • For the fetus: Testing of the amniotic fluid

  • For the newborn: Testing of blood and other fluids, brain imaging, spinal tap, and eye examinations

The diagnosis of toxoplasmosis in a pregnant woman is usually based on blood tests that detect antibodies against the parasite. (Antibodies are proteins produced by the immune system to help defend the body against attack, including by parasites.)

To determine whether a fetus has been infected, a doctor can take a sample of the fluid around the fetus (amniotic fluid) and test it for antibodies to the parasite and for the parasite's genetic material (DNA). The test, a procedure called amniocentesis, is usually done after the 14th week of pregnancy.

In some states, the infection is found in seemingly healthy newborns during routine newborn screening tests using a dried blood spot. If doctors suspect a newborn is infected, they test the blood and the fluid that surrounds the brain and spinal cord (spinal fluid). To obtain spinal fluid, doctors do a spinal tap (lumbar puncture). Other body fluids and the placenta may also be tested. Doctors do imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), of the brain to look for abnormalities typical of toxoplasmosis. Newborns are also given a thorough eye examination by an ophthalmologist (a medical doctor who specializes in the evaluation and treatment of all types of eye disorders) and hearing tests.


Some children have a severe infection and die early, whereas others survive but have long-term neurologic problems. Occasionally, neurologic problems (such as intellectual disability, deafness, and seizures) or eye problems such as chorioretinitis, develop years later in children who appeared normal at birth. Therefore, children with congenital toxoplasmosis should be closely monitored by doctors beyond infancy.


Pregnant women should avoid handling cat litter. If this is not possible, pregnant women should change the entire litter box every day because the toxoplasmosis eggs do not become infectious for about 24 hours after the cat excretes them. Woman also should wear gloves and then carefully wash their hands to reduce the risk of infection.

Pregnant women should thoroughly cook meat before eating it. Fruits and vegetables should be washed thoroughly or peeled, and all food preparation should be followed immediately by handwashing.

To reduce the risk of transmitting the infection to the fetus, infected pregnant women may be give the drug spiramycin. However, this drug does not treat the fetus.


  • For fetuses: Pyrimethamine and sulfonamides

  • For newborns: Pyrimethamine, sulfadiazine, and leucovorin

Pyrimethamine and sulfonamides may be given later in pregnancy if the fetus is infected.

Infected newborns with and without symptoms are treated with pyrimethamine, sulfadiazine, and leucovorin (a drug that prevents side effects of pyrimethamine).

Inflammation of the eyes is sometimes treated with corticosteroids.

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