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NIH study supports screening pregnant women for toxoplasmosis

A new blood test developed at the National Institute of Allergy and Infectious Diseases is giving researchers fresh insights into birth defects caused by toxoplasmosis infection.

Pregnant women can become infected with the parasite Toxoplasma gondii by eating undercooked meat or fish and from exposure to infected cat feces or soil. The parasite can then be transmitted to the fetus, where it has the potential to cause miscarriage, stillbirth, and serious birth defects of the eyes and brain.

Scientists used the new blood test to determine which strains of Toxoplasma are most likely to cause birth defects. They found that Toxoplasma strains predominant in North America are more likely to cause fetal problems than the strains prevalent in Europe. That's a significant discovery because, unlike many European countries, Canada and the United States do not routinely screen pregnant women for toxoplasmosis. Screening and treatment greatly reduces the likelihood that a baby will suffer long-term damage from mom's infection.

According to the NIH press release about the new study:

"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."

A Stanford study published last year reached a similar conclusion. I wrote in a press release:

Screening is needed because toxoplasmosis can occur even in pregnant women who carefully avoid known transmission methods. What's more, the infection can occur without any symptoms in the mother.

"There is a tragedy out there that can be prevented through thoughtful, low-cost serological screening of one of our most vulnerable populations - the mother-baby pair," said [study author Jose Montoya, MD]. "The sad part is that in the U.S., although we have the tools at both the medical and the lab level to detect and treat prenatal toxoplasma infections, we don't apply them."

In sum, evidence to support routine toxoplasmosis screening in pregnancy seems to be mounting. I hope the new findings prompt a serious evaluation of the cost-effectiveness and other practical concerns associated with implementing screening.

Image at left shows a form of toxoplasmosis-causing parasite that can be transmitted through the placenta to a fetus. At right, a Toxoplasma parasites (green) inside a cyst.

Previously: Patrick House discusses Toxoplasma gondii, parasitic mind control and zombies and Prenatal testing could spare babies from toxoplasmosis complications
Photo by R. McLeod, University of Chicago.

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