A woman can get toxoplasmosis by eating raw or undercooked meat or by contact with cat feces. Fortunately, a pregnant woman can follow some simple precautions that can reduce her chances of becoming infected. Because more than half of all pregnancies are unintended, all women who could become pregnant should follow these precautions.
What symptoms does toxoplasmosis cause in the baby?
Most newborns with toxoplasmosis show no obvious symptoms. However, about 1 in 10 infected babies has a severe infection evident at birth (3). These newborns often have eye infections, an enlarged liver and spleen, jaundice (yellowing of the skin and eyes) and pneumonia. Some die within a few days of birth. Those who survive sometimes develop mental retardation, severely impaired eyesight, cerebral palsy, seizures and other problems.
Without treatment, about 85 percent of infected babies who appear normal at birth develop problems months to years later (3, 4). These include eye infections that may affect sight, learning disabilities and hearing loss. Toxoplasmosis during pregnancy also can result in miscarriage, preterm delivery or stillbirth. (3, 5)
How common is toxoplasmosis?
Toxoplasmosis is one of the most common infections in the world. More than 60 million people in the United States may be infected (6). However, most have no symptoms, so they may not know they are infected. A small number of infected individuals develop symptoms that resemble the flu or infectious mononucleosis, including swollen glands, fatigue, muscle aches, malaise and fever. These symptoms may last for a month or longer.
Active infection normally occurs only once in a lifetime, followed by life-long immunity (protection). Although the parasite remains in the body indefinitely, it generally is harmless and inactive unless the immune system is not functioning properly (for example, if an individual has AIDS). Women who develop immunity to the infection before pregnancy are not in danger of transmitting it to their babies.
Can a woman find out if she is immune?
About 85 percent of women of childbearing age in the United States have never had toxoplasmosis and are susceptible to it (1, 2). Blood tests can show whether a woman has had toxoplasmosis. However, these tests are not routinely offered during pregnancy unless a woman's health care provider suspects she might have the infection. If the tests show that a woman has had toxoplasmosis, additional tests may be necessary to find out if the infection is a recent one (which could pose a risk to the fetus) or an old one (which does not pose a risk).
Women planning to become pregnant can discuss with their health care providers whether being tested before pregnancy is appropriate. If the blood tests show that a woman has not been infected, she should take precautions to prevent the infection during pregnancy, as should all women who have not been tested.
How can a woman prevent toxoplasmosis during pregnancy?Cat feces and raw or undercooked meat are the most important sources of this infection. A pregnant woman can help prevent toxoplasmosis by avoiding known sources of infection:
- Don't eat raw or undercooked meat, especially lamb or pork. Cook meat to an internal temperature of 160° F.; the meat should not look pink, and the juices should be clear (6).
- Wash your hands immediately with soap and water after handling raw meat. Never touch your eyes, nose or mouth with potentially contaminated hands.
- Clean cutting boards, work surfaces and utensils with hot, soapy water after contact with raw meat or unwashed fruits and vegetables (which can be contaminated by soil containing cat feces).
- Peel or thoroughly wash all raw fruits and vegetables before eating.
- Don't empty or clean the cat's litter box; have someone else do this. An infected cat (which usually appears healthy) can shed the parasite in its feces. The litter box should be emptied every day, because the stage of the parasite found in the cat's feces does not become infectious for 24 hours. If nobody else can change the litter box, wear gloves and wash your hands thoroughly after emptying.
- Don't feed the cat raw or undercooked meats.
- Keep the cat indoors to prevent it from hunting birds or rodents (which can be infected with the parasite and pass it on to the cat).
- Wear gloves when gardening. Outdoor soil may contain the parasite from cats. Keep your hands away from your mouth, eyes and nose, and wash your hands thoroughly when finished. Keep gloves away from food.
- Avoid children's sandboxes; cats may use them as litter boxes.
How is toxoplasmosis diagnosed and treated during pregnancy?
A health care provider who suspects that a pregnant woman has an active Toxoplasma infection may recommend blood tests. These tests require expert interpretation. Therefore, the Centers for Disease Control and Prevention (CDC) recommends that all positive test results be confirmed by a Toxoplasma reference laboratory (one with special expertise in diagnosing this disorder) (1). Health care providers can get more information by contacting the Toxoplasma Serology Laboratory at the Palo Alto Medical Foundation.
If the reference laboratory confirms that a pregnant woman has an active infection, the next step is to determine whether the fetus is infected. Prenatal tests, including amniocentesis and ultrasound, may help to determine whether the fetus is infected. If a fetus is suspected of being infected, the mother will be treated with the drugs pyrimethamine and sulfadiazine. This approach appears to reduce the frequency and severity of the newborn's symptoms (3, 4). The earlier the mother is treated, the less likely her baby is to have symptoms.
If tests show that the fetus is not yet infected, the mother may be given an antibiotic called spiramycin. Some studies suggest that spiramycin can reduce by about 60 percent the likelihood of the fetus becoming infected (3, 4). Spiramycin has not been approved for use in this country by the Food and Drug Administration (FDA) and is considered an experimental drug. However, providers can obtain it through the FDA by calling (301) 827-2335 (7).
How likely is an infected pregnant woman to pass toxoplasmosis on to her baby?
A woman who contracts toxoplasmosis during pregnancy has about a 50 percent chance of passing the infection on to her fetus (1). However, the risk and severity of the baby's infection depend upon when in the pregnancy the infection occurs. Studies suggest that, when mothers are infected in the first trimester (first three months of pregnancy), about 10 percent of fetuses become infected, as compared to about 30 percent in the second trimester and about 60 percent in the third (4). However, the earlier in pregnancy the infection occurs, the more serious the baby's symptoms tend to be.
How are infected newborns treated?
Infected babies should be treated with pyrimethamine and a sulfonamide (sulfadiazine or sulfadoxine). These drugs should be continued throughout the first year of life and, in some cases, even longer (1, 3).
A study by the U.S. National Collaborative Treatment Trial found that about 75 percent of infected babies (including those with severe infections present at birth) who received this treatment had normal intelligence, and none developed hearing loss (3). Unfortunately, this and other studies found that eye infections tended to recur in childhood (3, 8). Children who were re-treated with the two drugs generally did not suffer vision loss. Some treated babies still developed lasting disabilities, possibly because drug treatment may not reverse any brain or eye damage that occurred before birth.
Most infected babies who do not have symptoms at birth miss early treatment. They often are not diagnosed until they develop an eye infection or other problems, sometimes months or years after birth. Currently, two states (Massachusetts and New Hampshire) screen newborns for toxoplasmosis, allowing for early treatment of infected newborns.
What research is being conducted on toxoplasmosis in pregnancy?
Investigators continue to seek better ways to diagnose and treat toxoplasmosis during pregnancy, in order to prevent fetal infections. For example, a recent March of Dimes grantee is studying the role of a Toxoplasma protein in enabling the parasite to invade fetal cells. His goal is to develop drug treatment to prevent fetal infections. Scientists also are trying to determine whether it would be possible and beneficial to screen all newborns for this infection, so that infected babies would benefit from early drug treatment.
For more information
Read the fact sheet provided by the Organization of Teratology Information Specialists (OTIS).
References
1. National Center for Infectious Diseases, Centers for Disease Control and Prevention. Preventing Congenital Toxoplasmosis. Morbidity and Mortality Weekly Report, volume 49, RR02, March 31, 2000.
2. Jones, J.L., et al. Toxoplasma Gondii Infection in the United States, 1999-2000. Emerging Infectious Diseases, volume 9, number 11, 2003.
3. Remington, J.S., et al. Toxoplasmosis, in Remington, J.S., Klein, J.O. (eds.): Infectious Diseases of the Fetus and Newborn Infant, 5th edition, Philadelphia, W.B. Saunders, 2001, pages 205-346.
4. Montoya, J.G., Liesenfeld, O. Toxoplasmosis. Lancet, volume 363, June 12, 2004, pages 1965-1976.
5. Freeman K., et al. Association Between Congenital Toxoplasmosis and Preterm Birth, Low Birthweight and Small for Gestational Age Birth. British Journal of Obstetrics and Gynecology, volume 112, number 1, January 2005, pages 31-37.
6. Centers for Disease Control and Prevention (CDC). Toxoplasma Infection Fact Sheet, accessed 6/3/05.
7. Food and Drug Administration (FDA). FDA Public Health Advisory: Limitations of Toxoplasma IgM Commercial Test Kits. FDA, July 25, 1997, accessed 6/2/05.
8. Wallon, M., et al. Long-Term Ocular Prognosis in 327 Children with Congenital Toxoplasmosis. Pediatrics, volume 113, number 6, June 2004, pages 1567-1572.
September 2005 (R 4-07)
