Toxoplasmosis is an infection that can cause risks for an unborn baby. Caused by a parasite called Toxoplasma gondii (or T. gondii), toxoplasmosis in an adult generally results in mild flu-like symptoms or even no symptoms. However, if the infection is passed to a baby during pregnancy, it can harm the baby's various organs, including the brain and eyes. Treatment with antibiotics appears to reduce the risk for these problems.
Infection
Toxoplasmosis infections are acquired in one of three ways: handling cat litter or soil that has been contaminated by cat feces, which can contain oocysts of the T. gondii parasite; eating raw or undercooked meat from animals that have the parasite, or a newly-infected woman passing the infection on to her baby.
Effects
Toxoplasmosis can be passed to the growing baby through the placenta. In most cases, the baby either will not get toxoplasmosis or will not be adversely affected by it. However, in 20 to 30 percent of cases, the baby develops congenital toxoplasmosis, a severe infection. It is estimated that 400 to 4,000 babies with congenital toxoplasmosis are born in the United States each year (see Reference 1). Congenital toxoplasmosis can cause inflammation of and damage to the brain, eyes and liver. Some infected babies appear to be healthy at birth but later can develop consequences of the infection, including deafness and mental retardation.
Risk
The chance of a baby getting toxoplasmosis varies depending on the gestational age of the pregnancy when the mother acquires the infection. A study published in the journal "Lancet" in 1999 found that the transmission rate of the infection increased throughout the pregnancy. The transmission rate was only 6 percent at 13 weeks gestation but jumped to 72 percent at 36 weeks gestation. The effect on the fetus, however, is more severe when the infection occurs early in pregnancy.
Testing
A pregnant woman can be screened with a blood test early in pregnancy to determine if she is susceptible to toxoplasmosis infection. Some women may be exposed to T. gondii months or years before and develop immunity. If the test shows that a woman is not immune and she suspects she may have a toxoplasmosis infection, a couple of tests are available to see if the baby has been affected. Amniocentesis, which involves obtaining a sample of the fluid that surrounds the baby, can be performed to see if the parasite is present in the amniotic fluid. If it is present, ultrasound can be done to look for a smaller head size than normal or calcifications in the brain, which would suggest that the parasite has harmed the baby.
Prevention/Solution
Toxoplasmosis can be easily avoided by taking a few simple steps. A pregnant woman with cats should avoid cleaning the litter box if possible. If she must clean it, she should wear rubber gloves and wash her hands thoroughly afterward. She should limit gardening in areas that may have been contaminated by cat feces and wear gloves while gardening. She should avoid eating raw or undercooked meat or poultry. And finally, she should thoroughly wash all fruits and vegetables before eating them.
References
- "Morbidity and Mortality Weekly Report Recommendations and Reports"; Preventing Congenital Toxoplasmosis; A. Lopez et al; March 2000
- "Lancet"; Mother-To-Child Transmission of Toxoplasmosis: Risk Estimates For Clinical Counseling; D. Dunn; May 1999
