NoBlood

Jan B. Wade · #1 (**permalink**) 11-19-2003, 08:24 AM

Rare Infection Threatens to Spread in Blood Supply
By DONALD G. McNEIL Jr.

Published: November 18, 2003

parasitic infection common in Latin America is threatening the United States blood supply, public health experts say. They are especially concerned because there will be no test for it in donated blood until next year at the earliest.

The infection, Chagas disease, is still rare in this country. Only nine cases are known to have been transmitted by transfusion or transplant in the United States and Canada in the last 20 years.

But hundreds of blood recipients may be silently infected, experts say, and there is no effective treatment for them. After a decade or more, 10 to 30 percent of them will die when their hearts or intestines, weakened by the disease, explode.

Chagas is still little known in the United States, but in Mexico, Central America and South America, 18 million people are infected, and 50,000 a year die of it.

Experts expect it to become better known as new tests are developed.

"I wouldn't say that it's as rare as hen's teeth, but it's rare," said Dr. Ravi V. Durvasula, a Chagas expert at the Yale School of Public Health. "It's one of the top threats to the blood supply, but it's an emerging threat."

Because the disease is most common in rural areas from southern Mexico to northern Chile, the threat is greatest in American cities with many immigrants from those areas.

Across the United States, said Dr. David A. Leiby, a Chagas expert at the American Red Cross, the risk of getting a transfusion of infected blood is only about 1 in 25,000.

But in 1998 in Miami it was found to be 1 in 9,000, he said, and in Los Angeles the same year, he measured it at 1 in 5,400, up from 1 in 9,850 only two years earlier.

No more recent study of the blood supply has been done.

The only routine screening for Chagas now is in the standard set of questions asked of donors whether they come from or have visited a country where Chagas is endemic and whether they ever slept in a thatched hut.

But that often isn't reliable, said Dr. Louis V. Kirchhoff, a professor at the University of Iowa's medical school who researches Chagas in Guadalajara, Mexico, where the chance of getting infected blood is 1 in 126. Potential donors "are kind of leery of those questions," he said, and may not answer honestly.

Since 1989, several advisory panels to the United States Food and Drug Administration have recommended that all donated blood be screened for Chagas. But no test has been approved yet.

Last year, the F.D.A. invited diagnostics companies to create one, and the two largest, Abbott Laboratories and Ortho-Clinical Diagnostics, are trying. But representatives of the companies said they were under little deadline pressure. Abbott's test may be ready next year.

Little sense of urgency exists because "there are always new things that come up," Dr. Leiby said. Hepatitis and AIDS were followed by mad cow disease, West Nile virus and bacterial contamination of platelets, so "Chagas gets pushed to the side," he said.

Mary Richardson, a spokeswoman for Ortho, which hopes to have a test by 2005, added: "Clinical trials take time. There's only so much speeding up you can do."

Nonetheless, she added, "the F.D.A. feels it's the next biggest threat."

An F.D.A. spokeswoman said her agency did not like to rank all the threats to the blood supply including hepatitis, AIDS and West Nile virus but reiterated that "we would certainly recommend a Chagas test if one is developed."

Prevalence rates in Latin America vary widely, from 25 percent in Bolivia to 1 percent in Mexico.

It is not found on Caribbean islands like Puerto Rico, the Dominican Republic or Cuba.

In some countries, it is a serious threat to the blood supplies; in one Bolivian city, half of the blood was infected.

About 30 tests are used in different countries, but none meet F.D.A. accuracy standards. Some Latin American blood banks disinfect with gentian violet, but it is unpopular because it gives recipients a purplish tinge