Written by Gretchen Holm and Erica Roth | Published on July 17, 2012
Medically Reviewed by George Krucik, MD

What Is Toxoplasmosis?

Toxoplasmosis is an infection that is caused by a parasite. This parasite, called Toxoplasma gondii, can be found in cat feces and in undercooked meat, especially venison, lamb, and pork. Toxoplasmosis can be deadly for a fetus if the mother becomes infected. If you have heard that pregnant women should not scoop or clean litter boxes, this is why.

Most people who have toxoplasmosis never have any symptoms at all. According to the Centers for Disease Control and Prevention, over 60 million people in the United States are infected with the parasite (CDC, 2011).

What Causes Toxoplasmosis?

Toxoplasma gondii, a parasite, causes toxoplasmosis. You can catch it from contaminated meat that is raw or not thoroughly cooked. You can also get toxoplasmosis by drinking contaminated water. In rare cases, toxoplasmosis may be transmitted through a blood transfusion or a transplanted organ.

The parasite can also exist in feces. This means it can be found on some unwashed produce that has been contaminated with manure. Wash your produce thoroughly to prevent toxoplasmosis.

The parasite can also exist in cat feces.

According to the Cornell University College of Veterinary Medicine, although Toxoplasma gondii is found in nearly all warm-blooded animals, cats are the only known hosts. This means that the parasite’s eggs reproduce sexually only in cats (Cornell, 2008). The eggs exit the feline’s body through excretion. Cats don’t usually show symptoms of toxoplasmosis even though they are hosts.

People become infected with toxoplasmosis only if they accidentally ingest the parasite. This could happen when being exposed to contaminated cat feces. This is most likely when cleaning out a litter box without washing your hands afterwards. Pregnant women have an increased risk of passing toxoplasmosis to their unborn child in this manner. For this reason, you should ask someone else to take care of litter box maintenance during your pregnancy. If you absolutely must clean out the box yourself, protect yourself with gloves.

However, it is very rare for humans to get toxoplasmosis from cats. Generally speaking, house cats that are not allowed outside do not carry Toxoplasma gondii. Wild cats or outdoor cats that hunt are more likely to be hosts of T. gondi.

In the United States, the most common way to get infected with the toxoplasmosis parasite is by eating raw meat or unwashed fruits and vegetables (Cornell, 2008).

What Are the Symptoms of Toxoplasmosis?

Most people who have been infected with the parasite that causes toxoplasmosis show no symptoms and never realize they have contracted the condition.

In healthy people who show symptoms, a flu-like feeling is the most common. These symptoms include:

  • fever
  • swollen lymph nodes, especially in the neck
  • headache
  • muscle aches and pains

Occasionally, patients may complain of a sore throat. These symptoms can last for a month or more.

Toxoplasmosis is more serious for people who have weakened immune systems. For these people, symptoms can include:

When a fetus is infected, the symptoms may be mild or quite serious. Toxoplasmosis in your unborn baby can lead to a miscarriage, stillbirth, or death soon after birth.

How Is Toxoplasmosis Diagnosed?

Your doctor will typically perform a blood test to check for antibodies to this parasite. An antibody is a type of protein that your immune system produces when it is threatened by harmful substances called antigens. Viruses, bacteria, parasites, and fungi are all examples of antigens.

If you have ever been exposed to T. gondi, antibodies will be present in your blood. This means you will “test positive” for the antibodies. If your tests come back positive, you have been infected with this disease at some point in your life. A positive result does not necessarily mean that you currently have an active infection.

If your tests come back positive for antibodies, your doctor might do further testing to help figure out exactly when you were infected.

If you are pregnant and have an active infection, your doctor may test your amniotic fluid and the fetus’ blood. An ultrasound can also help determine whether the fetus has been infected. If your fetus is diagnosed with toxoplasmosis, you will probably be referred to a specialist. Genetic counseling will also be suggested. The option of ending the pregnancy, depending on the gestational age of the baby, may be offered as a possibility. If you continue the pregnancy, your doctor will likely prescribe antibiotics to help reduce your baby’s risk of symptoms.

How Is Toxoplasmosis Treated?

It may seem counter-intuitive not to treat a known condition. However, your doctor may recommend this if your toxoplasmosis does not cause any symptoms.

If you do show symptoms and need treatment, your doctor will typically prescribe two medications: pyrimethamine (Daraprim) and sulfadiazine. Pyrimethamine is also used to treat malaria. Sulfadiazine is an antibiotic. If you have HIV or AIDS, you may need to continue these medications for life. Pyrimethamine slows down your body’s absorption of vitamin B (folic acid), so your doctor may also have you take additional vitamin B while taking the drug.

Treatment during pregnancy is somewhat different. Your course of treatment will depend on whether your unborn child is infected and how serious the case is. Your doctor will talk with you about the best course for your particular case. You may be treated with the antibiotic spiramycin. This makes it less likely that your baby will acquire toxoplasmosis.

This treatment is more commonly used in Europe than in the United States, where spiramycin is considered an experimental drug by the Food and Drug Administration (FDA). However, your doctor can get it for you if he or she deems it necessary.

If your unborn baby has toxoplasmosis, pyrimethamine and sulfadiazine may be considered as a treatment. However, both drugs have significant side effects on women and the fetus, and are only used as a last resort. The potential side effects include suppression of the bone marrow that helps produce blood cells, and liver toxicity.

What Complications Are Associated with Toxoplasmosis?

The reason that pregnant woman should take special precautions to avoid toxoplasmosis is that it can be very serious—even fatal—for a baby infected in utero. For those who survive, toxoplamosis can have lasting consequences on the brain, eyes, heart, and lungs. The child may experience mental and physical developmental delay and recurring seizures.

In general, babies who are infected early during the pregnancy suffer from more severe issues than those infected later in the pregnancy. According to the Mayo Clinic, babies born with toxoplasmosis may have a higher risk of hearing and vision losses. Some children may be affected with learning disabilities (Mayo Clinic, 2011).

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