Screening for toxoplasmosis for all pregnant women and newborns is necessary

Feb 9 2005

Physicians found that signs, symptoms and identifiable risk factors are absent in more than half of the mothers of infants with congenital toxoplasmosis in a national study of children with this disease.

More than half of the pregnant women who were at risk for acute infection with Toxoplasma gondii could not be identified by history or routine examination. Therefore, the physicians recommend that systematic screening for acute acquired toxoplasmosis for all pregnant women in the United States during prenatal visits, as well as screening for congenital toxoplasmosis in all newborns, become standard medical practice. The group also emphasizes that confirmation of test results in reference laboratories and informed counseling are essential parts of the process.

An infection caused by the parasite Toxoplasma gondii, toxoplasmosis can be harmful and potentially lethal to the children of women who acquire the infection during pregnancy.

In the February issue of the The American Journal of Obstetrics and Gynecology, the researchers report that current clinical practice -- taking a careful history and performing a physical examination -- would identify only half of the at-risk mothers who have acquired the infection during pregnancy and have had infants with congenital toxoplasmosis. Screening through blood tests could have identified the rest, the researchers said.

"We have medicines that can help if we catch the infection and improve outcomes if we detect the infection early, but by only taking a careful history and examination we are missing many pregnant women and their infants who may benefit from treatment," said study co-author Rima McLeod, M.D., professor of ophthalmology and medical director of the Toxoplasmosis Center at the University of Chicago.

According to the Centers for Disease Control and Prevention, more than 60 million people in the United States probably carry the T. gondii parasite, but few have symptoms. The immune system usually keeps the parasite from causing illness. However, pregnant women should be cautious. If the infection is acquired for the first time while a woman is pregnant, it can cause serious problems. Infection of the fetus may cause severe eye and brain damage, and may result in crippling diseases in the newborn or later in life.

"Early detection and treatment of the T. gondii infection in the mother, fetus and infant can prevent or reduce the risks of ophthalmologic and/or neurologic damage," said Kenneth Boyer, M.D., chairman of pediatrics at Rush University Medical Center and a co-author of the study.

T. gondii infects humans through three principal routes: eating undercooked, infected meat; ingesting T. gondii oocysts that cats pass in their feces, with exposure occurring through cat litter or soil (examples include gardening, eating unwashed fruits and vegetables, water contamination); and a newly infected pregnant woman passing the infection to her fetus.

The physicians questioned the mothers of 131 children with confirmed congenital toxoplasmosis who were referred to the National Collaborative Treatment Trial. This is a study sponsored by the National Institutes of Health and is based in Chicago, but involves children throughout the United States.

The physicians gathered demographic data, including place of residence, age, race and socioeconomic status, and information about the mothers' exposures to undercooked meats, cat litter, raw eggs and more. The physicians also asked the mothers if they experienced any illnesses, such as flulike symptoms including headaches, night sweats and swollen lymph nodes, which can be symptoms and signs of this infection in older children and adults.

Only 8 percent of the mothers in the study were screened by serologic testing for toxoplasmosis during pregnancy. The physicians said the finding is consistent with the infrequent screening of pregnant women in the United States for this infection.

The group found that 52 percent of mothers couldn't recall an illness of any kind during pregnancy or identify risk factors, including ingestion of undercooked meats and or exposure to cat litter.

The physicians also found that demographics play no role in the occurrence of infections. "Acute toxoplasmosis and transmission to the fetus can affect individuals of any background and socioeconomic status," McLeod said.

In France and Austria, education about toxoplasmosis and screening for T. gondii is part of routine obstetrical care. Infection rates have been reduced by about 50 percent as a result of education. But this shows that other measures, such as blood tests during each month of pregnancy, are necessary so that doctors can identify the infection early. Treatment of the mother may help prevent the harmful consequences of the infection in the fetus.

Although most states require screening for a number of genetic and metabolic diseases in the newborn, including phenylketonuria, congenital hypothyroidism and congenital adrenal hyperplasia in the newborn, each of these genetic diseases is less common than toxoplasmosis. But there is no systematic program for screening for toxoplasmosis during pregnancy in the United States.

More than 10 years ago, Jack Remington, a co-author of the study and a professor of medicine at Stanford University School of Medicine and Marcus Krupp research chair and chairman of the department of immunology and infectious diseases at the Research Institute, Palo Alto Medical Foundation, wrote "the time has come" to better address the problem of this significant and treatable cause of loss of sight, hearing and cognition. This study indicates again that to detect this infection so it can be treated, systematic obstetrical and newborn screening for toxoplasmosis are needed. The authors suggest that this is long overdue in the United States.

"Clearly, we need to be doing more than we currently are doing to prevent this congenital infection and adverse consequences of the infection in the fetus and infant," McLeod said. "Education is important, but it is not sufficient."