Toxoplasmosis Congenital Disease

Pregnancy and Cats

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Pregnant women are often warned to stay away from kitty’s litter box because of toxoplasmosis, a parasitic disease of cats. Toxoplasmosis (or Toxo) is spread to humans through cat feces and can lead to severe health issues for unborn babies.

Species Name: Toxoplasma gondii

Type of Microbe: Protozoa

Interestingly, cats are a necessary host for the toxoplasma life cycle. However cats are a necessary part of the Toxo lifecycle, but most infections occur far away from cats.

People are often infected because of a cat - but not from a cat. They can be infected later in the lifecycle.

After a cat ingests an infected small animal, such as a rodent or bird, the protozoa invade cells of the cat's intestine. The parasite next undergoes several developmental changes to become the infective form, or “oocyst,” and is released into the environment in cat feces. The parasite can then invade the body of another animal or human, burying itself into skeletal muscles, heart muscles, and the brain. It forms cysts, and can remain there throughout one's entire life.

Toxoplasmosis is spread through:

  • food (undercooked meats, especially pork, lamb, and venison that may carry Toxo cysts)
  • directly from cat feces
  • from food or water that has been contaminated - especially from soil or water - with Toxo (Sometimes the transmission of Toxo from kitty litter or feces to soil or water is not as obvious as might be expected. Feral cats or trash disposal may be responsible.)
  • blood transfusion
  • organ transplantation
  • mother-to-child transmission (congenital infections)

The parasite is not infectious until 1 to 5 days after being excreted by an infected cat, but it can survive in the environment (or litter box) for over a year.

Risk Factors

Toxoplasma can infect anybody, but the consequences are more severe in people whose immune systems are weakened, such as those with HIV.

The infection can cause particularly worrisome problems for a fetus if the infection occurs in a pregnant woman.


For most healthy people, toxoplasmosis usually has little or no symptoms. Approximately 10 to 20% of patients will develop mild flu-like symptoms that last for several weeks or more, but resolve without any treatment. Some develop swollen glands (or lymph nodes), such as in their neck (cervical lymph nodes). 

If a pregnant woman gets infected, the infection can be passed to the fetus, leading to possible miscarriage, stillbirth, or birth abnormalities, including enlargement or smallness of head. In many instances, babies born with toxoplasmosis do not show any symptoms at birth, but can later develop loss of vision, mental disability, and seizures.

There are other more serious infections that Toxo can cause. Sometimes the disease can affect the eye. This can be common in areas where contamination is common, but is not that common in the US. It can cause temporary or permanent vision loss. It can cause scarring of the retina.

For people with significant immunosuppression, such as those with advanced AIDS or who are receiving high-dose chemotherapy, there is the risk of reactivating the toxoplasma that was previously controlled, which can have serious consequences, such as causing a serious encephalitis, a brain infection that can cause confusion or more serious consequences if not properly treated.


Clinical diagnosis can be difficult. A swollen lymph node may be key to the diagnosis. In general, though, the diagnosis is made if a blood sample is sent specifically for Toxoplasmosis. This blood test looks for antibodies against Toxoplasma. The specific antibody type can help clinicians to estimate when the infection occurred. Less commonly used methods of diagnosis include microscope examination of tissues or body fluids for presence of the parasite. Detection of Toxoplasma DNA in amniotic fluid can also be used to determine if a fetus is infected.


For healthy people, the prognosis is generally good, with no long-term side effects.

For pregnant women, infection of the fetus has more severe consequences, including eye or brain damage at birth, or blindness or mental disability later in life.


Most healthy people recover without any treatment. Pregnant women and infants can be treated with drugs, usually a combination of pyrimethamine, sulfadiazine, and folinic acid, but the parasite cannot be completely eliminated. There are alternative regimens for people with certain drug allergies.


Wear gloves when gardening (to avoid contact with cat feces in the soil), and keep outdoor sandboxes covered (to keep out infected cats). Follow safe kitchen practices, especially when cooking meats (70 degrees Celsius for 10 minutes to kill the parasite). To keep your cats Toxoplasma-free, don’t let them eat raw or undercooked meats, and keep them indoors. For pregnant women, avoid changing the kitty litter (and make sure whoever does the kitty litter changes it daily to keep it clean), and stay away from stray cats or kittens.


Toxoplasmosis. Department of Health and Human Services. Centers for Disease Control and Prevention.

Toxoplasmosis. Parasites and Health. Laboratory Identification of Parasites of Public Health Concern. Centers for Disease Control and Prevention. Accessed: February 10, 2009.

PHE Toxoplasmosis