Toxoplasmosis: Do You Know How to Stay Safe?

Written by the Healthline Editorial Team | Published on March 15, 2012
Medically Reviewed by Dominic Marchiano, MD

What Do I Have?

Toxoplasmosis is a relatively common infection caused by the Toxoplasma gondii parasite. Children and adults who have healthy immune systems do not suffer long-term consequences and usually experience mild or no symptoms. Because the symptoms are so minor, many adults have had toxoplasmosis sometime in their lives without even knowing it. In contrast, those with weaker immune systems (due to HIV or cancer, for example) are at a much greater risk for serious complications, including damage to the eyes, brain, lungs, and heart. A baby in the early stages of development (still in the mother's womb) also has poor immune defenses and is therefore at greater risk for complications due to toxoplasmosis.

Cats and Toxoplasmosis.

The Toxoplasmosis gondii parasite must develop inside a cat before it can infect other animals, including humans. You do not necessarily have to own a cat, however, in order to get toxoplasmosis.

There are several ways humans can become infected with toxoplasma:

  • eating contaminated food -Toxoplasma cysts may be present in undercooked meat (such as beef, lamb, or pork) or on fruits and vegetables that have come into contact with contaminated soil or cat feces;
  • inhaling sporulated cysts (oocysts) from contaminated dirt or cat litter -The development of toxoplasma typically begins when a cat eats meat (often rodents) containing infectious toxoplasma cysts. The parasite then multiplies inside of the cat's intestines. Over the next several weeks, millions of infectious cysts are shed in the cat's feces through the sporulation process. During sporulation, the cyst walls harden while the cysts enter a dormant, but infectious stage for up to one year; and
  • acquiring it from an infected person -This only happens when an infected mother transmits the parasite to her baby in the womb (the parasite crosses the placenta) or if a person receives a transplanted organ or blood transfusion from a person infected with toxoplasma.

Patients who have toxoplasmosis, including young children or babies infected before birth, do not shed the parasite and are not contagious.

How Common Is Toxoplasmosis?

The frequency of toxoplasmosis varies greatly worldwide. It is most common in Central America and central Africa, and much less common in the U.S. This variation can be explained partly by climate since temperature and humidity affect how long toxoplasma cysts remain infectious. Local culinary customs also play a role; areas where meat is served raw or undercooked have higher rates of infection. The use of fresh meat that has not been previously frozen is also associated with a greater risk of infection.

Once you have been infected with toxoplasma, you will have antibodies in your blood for the rest of your life. (Antibodies are produced by your immune system to combat specific infectious agents that have entered your body.) In the U.S., the rate of toxoplasma infection in women of childbearing age is 3 to 30%, depending on part of the country. On average, about 10% of reproductive-age women in the U.S. have had toxoplasmosis; in some countries, this percentage may be as high as 70 to 80%.

Approximately nine out of 10 pregnant women in the U.S. are susceptible to toxoplasmosis; however, infection during pregnancy is relatively rare. In fact, less than one out of every 1,000 pregnant women develops toxoplasmosis. (In contrast, in approximately one out of every 100 pregnant women develops the infection.)

What Are the Risks of Toxoplasmosis During Pregnancy?

In the U.S., about one out of every 10 women of reproductive age has previously been infected with Toxoplasma gondii and is immune from further infection. The remaining 90% of women are at risk.

Toxoplasma infection during pregnancy can be serious because the parasite can cross the placenta and infect the baby. The baby, then, may suffer damage to the eyes, brain, heart, and lungs. It is also important to know that the mother is at increased risk for miscarriage when she has an acute toxoplasmosis infection.

In an infected pregnant woman, the chance of the parasite also infecting her baby is related to how far along the pregnancy is when the infection occurs. If infection occurs during the first trimester of pregnancy, the rate of transmission from mother to baby is 15%, while infections during the third trimester are transmitted 60% of the time. The majority of babies contract infection within the last few months of pregnancy, though, most have either no problems or only a mild infection. The likelihood of a fetal infection causing severe damage is greatest when the infection occurs early in the pregnancy. Five percent of pregnancies infected early on result in miscarriage, and 10% of surviving babies suffer severe consequences, including death.

What Are the Signs and Symptoms of Toxoplasmosis?

Most pregnant women who have toxoplasmosis experience few, if any, symptoms. One out of every 10 women experience swelling of the lymph nodes in the neck, low-grade fever, muscle aches, fatigue, and headache. Keep in mind, though, that experiencing these symptoms does not definitely indicate toxoplasmosis. If you are concerned, you should make an appointment with your doctor.

What Are the Consequences of Toxoplasmosis During Pregnancy?

Infection of the baby while in the mother's womb is called congenital infection. Some fetuses demonstrate signs of infection on ultrasound, including abnormalities in the brain and/or liver. Following infection, toxoplasmosis cysts can be found in the baby's organs; however, the most serious damage occurs as a result of nervous system infection. Specifically, the baby's brain and eyes may be damaged, either in utero (in the womb) or after birth, and may cause visual impairment or blindness, mental retardation, and developmental delay. A mother who is infected during the first few months of pregnancy is at greater risk of miscarriage.

Toxoplasmosis and AIDS.

HIV (the virus that causes AIDS) weakens the immune system. This makes the possibility of an HIV-positive person contracting multiple other infections more likely. Women who are pregnant and have HIV are at a greater risk of developing toxoplasmosis and of having serious problems from the infection. All pregnant women should be tested for HIV. Those who test positive should discuss the prevention of toxoplasmosis (as well as other opportunistic infections) with their doctor.

How Is Toxoplasmosis Treated During Pregnancy?

If you develop toxoplasmosis during pregnancy, you have several treatment options. The most extreme of these is termination of pregnancy, which is only suggested when a woman develops an infection between conception and her 24th week of pregnancy.

Generally, tests are performed to determine if the parasite has already crossed the placenta. If there is no evidence of infection in your baby, your doctor may prescribe spiramycin (a macrolide antibiotic) for the rest of your pregnancy, which appears to reduce your baby's risk of infection. If your baby is infected, your doctor will probably prescribe a combination of pyrimethamine (Daraprim) and sulfadiazine for the remainder of your pregnancy. Your baby will usually be treated with these antibiotics for up to one year after birth. However:

  • because pyrimethamine may cause fetal malformations, a woman should only begin treatment after her 14th week of pregnancy;
  • sulfadiazine may interfere with fetal blood cell formation, so a woman should also take folinic acid to counteract this; and
  • sulfadiazine treatment should end as close to the baby's due date as possible.

Prevention

Can Toxoplasmosis Be Prevented?

Eating contaminated meat or produce or inhaling microscopic toxoplasmosis cysts or spores are the most common means of toxoplasmosis transmission. You can reduce your risk of infection by:

  • eating fully cooked meat. You should avoid rare or tartare meat;
  • washing raw vegetables and fruit thoroughly;
  • washing raw vegetables and fruit thoroughly;
  • washing your hands thoroughly after handling raw meat or vegetables. You should avoid touching your eyes or mouth while preparing raw foods; and
  • washing your hands thoroughly after handling raw meat or vegetables. You should avoid touching your eyes or mouth while preparing raw foods; and
  • avoiding cat feces. If you have a cat, change the litter box every two days and periodically wash the litter tray with boiling water. Wear gloves and a mask when you change the litter box. Also, keep your pet indoors and do not feed it raw meat.

These preventive measures can reduce your risk of infection by at least 50%. There are no vaccines for toxoplasmosis and no medications that can be taken to prevent the infection.

If you are planning a pregnancy, you should practice the preventive measures outlined above. In addition, you should see your doctor at least three months before becoming pregnant to discuss your risk factors. Your doctor can perform a blood test to find out if you have had toxoplasmosis before and are therefore immune. (Remember, your body produces antibodies after an initial infection.) If your blood test shows that you have never been infected, you should continue to practice prevention measures and have an additional test as you progress through your pregnancy.

Should Every Pregnant Woman Have a Blood Test for Toxoplasmosis?

This is a controversial question, and the best answer is probably determined by considering the actual risks. First, most infants who are born with congenital toxoplasmosis in the U.S. have mild infections that do not cause long-term problems. Second, toxoplasmosis is relatively rare in the U.S.(when compared to some European countries), and false-positive tests results are relatively common. If every pregnant woman were tested, only about one in 60 women who tested positive would actually have toxoplasmosis. In addition, testing a baby for the disease can cause more problems (for example, an unnecessary pregnancy termination) than the number of mothers and babies who would likely benefit from treatment.

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