Information about Toxoplasmosis

Overview of Toxoplasmosis

Toxoplasma gondii causes the disease toxoplasmosis. T. gondii is a small parasite and very commonly infects humans. It is acquired from stages of the parasite that persist in a latent encysted form in meat and when a stage of the parasite that is excreted by members of the cat family contaminates the environment and humans or other animals ingest them. An acutely infected cat excretes 20 million oocyst forms of the parasite over about two weeks, even one is infectious and the oocyst can remain infectious in warm moist soil for up to a year and in water for up to six months.

The parasite causes eye and brain damage in a baby, if untreated, when a mother is infected for the first time while pregnant and passes the parasite to her child. The incidence of such congenital infection varies with locale and is not well-defined. For example, congenital infection is estimated to affect approximately 1 in 5000 babies born in the US, 1 in 3000 born in France, and 1 in 300 born in Panama.

The acute infection in older children and adults may be without symptoms, cause flu like illness or enlarged lymph glands. Eye disease or other destruction of other tissues by the parasite such as infection and inflammation of heart or brain occurs in some older children and adults who acquire the infection but these manifestations are not frequent.

This latent parasite occurs very commonly in people infecting approximately a third to a half of all humans, or approximately 2 billion people worldwide. This latent parasite can cause active disease if a person becomes immune compromised from conditions such as malignancies, autoimmune diseases, or transplantation and their treatments or AIDS. It also can recrudesce and cause later eye disease in congenitally infected children and in some older children and adults who acquired the parasite after birth.

Treatment can prevent transmission of the parasite from mother to child as well as treat and prevent adverse consequences of the infection if diagnosed and treated early.

Toxoplasmosis refers to the disease caused by the parasite Toxoplasma gondii. The organism Toxoplasma gondii is related to parasites that cause malaria, cryptosporidial diarrhea and babesiosis. The parasite is 3-5 micron in length and visible with a microscope. In the acute infection the parasite is in a form that multiplies rapidly called a "tachyzoite." If the immune response to the parasite is normal, the parasite then forms a cyst that contains slowly replicating "bradyzoites." Bradyzoites persist for the remainder of an infected individual's/animal's life. If a member of the cat family eats meat containing bradyzoites in cysts, or oocysts excreted by other cats, male and female parasite gametes form in the cat intestine. These gametes created highly infectious oocysts which are excreted for several weeks. Oocysts then are present in materials contaminated by cat feces (e.g., cat ltter, garden soil, sandboxes, or fruits and vegetables that come into contact with cat feces and then are not thoroughly washed). Only members of the cat family excrete oocysts. All animals can be infected by bradyzoites and oocysts.

The Parasite

The medicines available for treatment of active infection have toxicities. No medicines currently available can eliminate the latent form of the organism which results in risk for recurrent disease. Better medicines to treat the active and chronic latent infection are needed.

A chronically infected mother‘s immune response (if she is not immune compromised) prevents transmission of the parasite to her baby. This observation provides support for the development of vaccines which will elicit a similar protective immune response for humans.

The effect of a chronic brain infection in 2 billion people, or some of them who might be genetically susceptible to a more extensive inflammatory process on subsequent neurodegenerative diseases, is unknown.

Bradyzoites in a Cyst
Tachyzoites in a Cell

How Can I Get It?

Toxoplasma gondii is acquired from meat not cooked to well done or oocysts in materials contaminated with cat feces. A woman who is infected for the first time while pregnant may transmit the infection to her baby while she is pregnant. Immunocompromised individuals may develop serious medical problems from acute or chronic Toxoplasma infection.


Currently 30% to 50% of people throughout the world, 2 to 3 billion people in 2006, are infected with Toxoplasma gondii. The infection is most commonly passed from mother to fetus during pregnancy. Congenital infection occurs in between 1 in 1000 and 1 in 15,000 live births in the US. Immunologicaly compromised persons, such as those with autoimmune disorders, organ and bone marrow transplants and AIDS, are also at risk of developing the disease.

Incidence of infection in those of childbearing age (outside parentheses) and of children under the age of 10 years (inside parentheses).
Source: Centers for Disease Control and Prevention, National Center for Infectious Diseases. “Food-Related Illness and Death in the United States,” Emerging Infectious Diseases, Vol. 5, No. 5, 1999.


This infection can be diagnosed through the use of blood tests, amniocentesis, isolation of the parasite, and characteristic microscopic appearance of tissues. Reference laboratories for assistance with diagnostic tests can be found on our Links page.

Cost of Apicomplexan Parasite Diseases

The estimated costs for care of children born with toxoplasmosis in one year in the US are between one half and eight billion dollars. Disease caused by this infection in immune compromised individuals is costly and frequent.

There are more than 4000 species of apicomplexan parasites. The apicomplexan parasites that cause diseases in humans include Toxoplasma gondii (top) that infects two billion people worldwide and can harm the brain and eye of a baby or those who are immunocompromised. Malaria (middle) kills one million children a year. Cryptosporidium parvum (bottom) causes diarrheal disease and dehydration.


There are practical ways you can avoid infection.

If a woman becomes infected with Toxoplasma for the first time while she is pregnant, her unborn baby may also be infected. Infection of a baby while in utero may result in damage to the baby's brain, eyes, ears, or in the baby's death. Infection is acquired mainly by eating foods or handling materials such as sand in a sandbox or garden soil contaminated with cat feces or from eating undercooked meats that contain Toxoplasma.

If you are acutely infected with Toxoplasma while you are pregnant, although you may have symptoms or signs such as a flu-like illness or enlarged lymph nodes, chances are your infection will be so mild that you may never realize you have been infected. While you feel fine, your unborn child is at risk of acquiring the disease from you and the results can be tragic.

Nearly 9 out of 10 pregnant women in the United States are at risk of being infected with Toxoplasma during pregnancy. the other 10% are immune due to infection acquired before the pregnancy. To know whether you are immune, your doctor must have your blood tested for antibody to Toxoplasma.

Every woman should know if her unborn child is protected against toxoplasmosa. If you are tested by your doctor and are found to be non-immune, you should be sure to follow the precautions listed below:

Avoid contact with materials potentially contaminated with cat excrement. Have someone else dispose of the contents of your cat's litterbox and have them clean the litterbox immediately with boiling water. Avoid sandboxes where cats have access, and cover them to prevent their utilizing a sandbox as a litterbox. Do not feed your cat raw meat.

Eat meat only when it is cooked to "well done". For example, do not eat meat tartare or "rare" meat.


Wash your hands after handling bloody (raw) meat and before eating. Keep your hands away from your eyes while preparing uncooked meat. Wear gloves while gardening.

Follow your blood antibody test for Toxoplasma in conjunction with your doctor. If acute infection occurs, detection and treatment can protect your baby.

Wash food such as green salads and fruits, especially if it is to be eaten uncooked.

Toxoplasmosis Research
Institute and Center

Chicago, IL
nstitute and Center
Chicago, IL