Prenatal toxoplasmosis tests: medical advances, backward policy?

Prenatal toxoplasmosis tests: Medical advances, backward policy?

Toxoplasma gondii is a widespread parasite infecting, among others, about 35 percent of the U.S. population and up to 80 percent of Parisians. Most of these people are unaware of their infection because they have healthy immune systems to keep the parasite at bay. But fetuses, with their underdeveloped immune systems, are not so lucky. Of women who first become infected with the parasite during pregnancy, 50 percent pass it on to the fetus. And depending on the time of infection, congenital toxoplasmosis can cause death, mental retardation, epilepsy or blindness. In most cases the infected child appears healthy at birth; the first symptoms may arise anytime from a few months to nine years later.

In light of these serious repercussions, France and Austria have mandated prenatal testing for T. gondii. And as evidenced by a recent study of 746 infected pregnant women, French researchers in particular have come far in developing accurate prenatal toxoplasmosis test- including blood and amniotic fluid tests and ultrasound examination of the fetal brain-for both mother and fetus. Such tests enable patients to make more informed decisions about whether or not to terminate a pregnancy, Fernard Daffos of the Hopital Notre Dame de Bon Secours in Paris and his colleagues write in the Feb. 4 NEW ENGLAND JOURNAL OF MEDICINE.

Prenatal tests also give physicians a chance not only to minimize the parasite's effects but also to protect the fetus from infection in the first place. Daffos's group reports some success in treating infected fetuses with antibiotics while in the womb and concludes that "prenatal therapy in women who wish to continue their pregnancies reduces the severity of the manifestations of the disease."

In addition, Daffos's group discovered that the percentage of fetuses that became infected with the parasite was considerably lower than what was found in their previous studies. The researchers attribute this difference to immediately treating the infected women in the recent study with the antibiotic spiramycin. This finding, they say, is indirect evidence that spiramycin can limit placental infection by the parasite (which can take weeks to move from mother to fetus) and can reduce the chances of congenital transmission. (In the United States, physicians treating infected pregnant women must get permission from the Food and Drug Administration to use spiramycin, which is also used in other countries to treat strep throat and the like.)

Uninfected French women are tested monthly for T. gondii once they become pregnant, but in the United States, physicians rarely perform either pre- or postnatal tests for the infection, according to Jack S. Remington, a infectious disease specialist at the Stanford University Medical Center. While data for U.S. births are scarce, it's been estimated that as many as 1 in 1,000 U.S. children are born with congenital toxoplasmosis, which is more common than congenital German measles, syphilis, phenylketonuria (a disease that causes brain damage) and other maladies for which physicians routinely test.

With its lack of commitment toward T. gondii testing, says Remington, "the medical community in the United States is either oblivious to the problem or they have simply turned their back on it."

Moreover, he adds, U.S. physicians do little to educate pregnant women on how to prevent infection, which usually comes from eating undercooked meats or from touching cat feced when gardening or disposing of cat litter. Healthy women who have been exposed before becoming pregnant needn't worry about infecting the fetus, because their antibodies can control the parasite. In France, where more people eat undercooked meats, most pregnant women have been previously exposed to the parasite, whereas in the United States, most pregnant women have not and so are at risk.

In an editorial accompanying the French results, Remington and Robert McCabe at the University of California Medical School at Davis urge U.S. health officials to begin prospective trials of the benefits and costs of T. gondii screening programs. In Massachusetts, officials have already decided that, at a cost of $5 million per year, they couldn't afford a prenatal screening program. Instead, they have started a pilot program to add T. gondii tests to the battery normally given to newborns. New Hampshire and Illinois are the only other states considering such newborn testing.

Remington says he hopes that U.S. health officials will pay more attention to toxoplasmosis, especially now that toxoplasmosis encephalitis (brain inflamation) has become the most common opportunistic infection among AIDS patients, whose immune systems can no longer keep the parasite in line. The disease is predicted to affect up to 30,000 U.S. AIDS patients by 1991. Remington, who is involved in an international study of toxoplasmosis encephalitis, says he has great hopes "not only that we will be able to define better therapies for these patients, but also that there will be some fallout to the woman and the newborn."