Scientists have identified the strains of the Toxoplasma gondii parasite most often associated with miscarry, premature birth and birth defects, but testing of pregnant women in the United States is rare.
The National Institutes of Health (NIH) has announced that researchers in a study funded by the NIH and National Institute of Allergy and Infectious Diseases (NIAID) have identified two strains of the Toxoplasma gondii protozoan parasite prevalent in the United States that are associated with severe illness in unborn fetuses and newborns of infected mothers.
Infection with T. gondi strains causes toxoplasmosis, an infection identified by the Centers for Disease Control (CDC) as a leading cause of death attributed to foodborne illness.
People can contract T. gondi from drinking contaminated water, eating unwashed garden vegetables or undercooked meat, or from hands, cutting boards or utensils that come in contact with raw, contaminated meat. People can also get the parasite by contact with feces of an infected cat.
Most of the 60 million Americans with toxoplasmosis show few symptoms because their immune system keeps them from getting sick. However, people with compromised immune symptoms and pregnant women can suffer severe consequences of toxoplasmosis infections. Women who contract toxoplasmosis during pregnancy may or may not show any symptoms but can suffer miscarriage or premature birth, and their baby can have severe eye or brain damage (eye disease, hydrocephalus or intracranial calcifications).
T. gondi tests currently available in the U.S. are broad and show only if a person has ever been infected with any of the fifteen strains of T. gondi. Doctors then attempt to estimate the time of infection, because it is important to know if the infection is recent in pregnant women.
Researchers in the study used a new experimental blood test developed by scientists at the NIAID to test for T. gondi in blood samples collected between 1981 and 2009 as part of the National Collaborative Chicago-Based Congenital Toxoplasmosis Study. They found strains called Type II and NE-II in the samples, with the NE-II strain more likely associated with premature birth and infants with severe manifestations of disease.
“If undetected or untreated, congenital toxoplasmosis can have serious consequences for a child’s quality of life,” noted NIAID Director Anthony S. Fauci, M.D. “The findings from this study support the value of screening for toxoplasmosis to identify patients who could benefit from treatment.”
France has a national prenatal and postnatal toxoplasma screening program. Infected pregnant women undergo treatment that reduces risk of mother-to-child transmission and reduces eye and brain damage in infected unborn fetuses.
“In the United States, obstetrical screening for Toxoplasma infection is rarely practiced,” said lead study author Rima McLeod, M.D., of the University of Chicago. “This new study underscores the value of identifying all patients who will benefit from treatment and suggests that widespread screening and treatment of pregnant women who are infected could prevent infants from suffering eye and brain damage due to congenital toxoplasmosis.”
The study Prematurity and Severity Are Associated With Toxoplasma gondii Alleles (NCCCTS, 1981–2009) appears in the May 1, 2012 issue of Clinical Infectious Diseases.