One in 3,800 donors in the Los Angeles area tested positive for Chagas, a deadly disease that is mainly found in Latin America

Rong-Gong Lin II:

A little-known but potentially deadly parasite from Latin America has become one of the latest threats to the blood and organ supplies in the United States, especially in Los Angeles, where many donors have traveled to affected countries, health officials say.

Last year, two heart transplant patients at different Los Angeles hospitals contracted the parasitic disease, called Chagas, causing health authorities to issue a national bulletin. Within months, both patients subsequently died, although not directly from Chagas, according to the U.S. Centers for Disease Control and Prevention.

The parasite, which is generally passed to humans from a blood-sucking insect that looks like a striped cockroach, can feed over years on tissues of the heart and gastrointestinal tract. After decades, tissues can be eroded so much that the organs fail.

Insect transmission of the parasite in the United States is rare, but public health and blood bank officials have been concerned about its increasing prevalence in the blood supply.

In 1996, using an experimental test, the American Red Cross found that one in 9,850 blood donors in the L.A. area tested positive for the parasite, Trypanosoma cruzi. Two years later, it was one in every 5,400. By 2006, a more refined test detected the parasite in one in 3,800 donors. About 10% to 30% of infected people develop symptoms of chronic disease, experts say.

By contrast, HIV, which blood banks screen for, shows up in one of every 30,000 donors, said Susan Stramer, executive scientific officer for the Red Cross.

If caught early, strong anti-protozoal drugs such as nifurtimox can bring the parasite to undetectable levels or, in some cases, eliminate it entirely.

If the parasite is given the chance to multiply over years or decades, however, those infected may have to be treated with heart-regulating drugs or get a pacemaker or heart transplant.

The U.S. Food and Drug Administration approved a test suitable for widespread screening in December. Blood banks have now begun systematically checking their supplies for the Chagas parasite.

By late January, the American Red Cross and Phoenix-based Blood Systems, which collect about 65% of the U.S. blood supply, had started screening blood for T. cruzi. Other banks, including the Blood Bank of San Bernardino and Riverside Counties, have no immediate plans for screening but are monitoring test results from banks that are using the test. In late February, the CDC reported that the "FDA is expected to recommend implementation of the test by all blood-collection establishments."

No organ donors in the United States are now being screened for the parasite, although the organ procurement agency that covers much of Southern California plans to begin testing some donors in mid-April. At first, the screening will be focused on people who have lived in or traveled to rural parts of Latin America, said Thomas Mone, chief executive of the agency, OneLegacy.

In Latin America, about 10 million to 12 million people are believed to be infected with the Chagas parasite. As many as 1 million of them are expected to die from the disease unless there are advances in treatment, according to Dr. James Maguire, a University of Maryland expert on the disease.

"Chagas is very, very prevalent in South and Central America," said Marek Nowicki, a USC blood-disease expert who studied the effect of Chagas on the Southern California organ supply with the National Institute of Transplantation.

"The number of [immigrant] Latinos in Southern California, Texas and other parts of the United States are growing, but especially in L.A., a large proportion of organ donors are Latino," Nowicki said. "They're basically bringing with them the disease prevalence in the area they used to live."

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