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Florida Blood Services to help test for deadly bug

The blood bank targets a parasitic infection that kills 50,000 each year, mostly south of the border.

ST. PETERSBURG - It is not pretty.

"It looks kind of like a roach," said Dr. German F. Leparc, chief medical officer for Florida Blood Services in St. Petersburg.

Really, the triatomine bug is even uglier. A roach crossed with a mosquito.

But the disease it carries is uglier still. Chagas disease, a parasitic infection, already is a leading killer in Central and South America and could become a threat in the United States.

Worried researchers are trying to keep that from happening. Leparc is one of them.

"As we become a more global society, we have more immigrants from areas where this is endemic," Leparc said. "The potential exists" for Chagas to spread.

Chagas infects as many as 18-million people worldwide and kills about 50,000 people a year. There is no cure.

In North America, there have been eight documented cases spread in another way: through blood transfusions from people already infected. One of those occurred in Miami in 1999.

"We know it's a disease that can be spread by blood transfusion," said Dr. Steven Kleinman, chairman of the transfusion-transmitted diseases committee of the American Association of Blood Banks. "Currently, we think the risk of transmission of Chagas is very low. But we recognize it is a problem."

That's why the few companies that produce screening tests for donated blood are working to develop a test for Chagas. Leparc will soon begin research to help develop one potential test. Florida Blood Services will be one of a handful of sites around the country working on the test.

The company Leparc is working for won't allow him to name it, Leparc said. But two of the largest companies that already produce tests for screening blood, Ortho-Clinical Diagnostics and Abbott Laboratories, have publicly said they're working on a Chagas test.

Even for those who become infected through blood in the United States, the disease will reach back to the same place: to a country further south, in the home of someone poor, someone sheltered only by adobe walls and a thatched roof.

Here is where the triatomine bug lurks.

It preys on the poor when they are most vulnerable.

As the human s sleeps, each breath they expel signals the bug. It senses the carbon dioxide in each spent breath. It flies down from the roof, or out from some hidden crack in the wall, down to the face of its victim.

This is how it earned its nicknames. In Brazil, the bug is "the barber," in other places, "the kissing bug."

It bites, and it sucks blood. The bug eats, then defecates. It deposits parasites that enter the victim through the wound or when a person scratches or rubs the area.

That's when things turn deadly. The bug's bite isn't so bad, but the parasite can kill.

The parasite is called Trypanosoma cruzi, and it's a little smaller than the red blood cells that it travels with once it enters the bloodstream.

Some victims get signs of an infection, such as fever, fatigue or a swollen eye, right away. In a few people, usually very young children, the infection causes brain damage and death. But in most people, any symptoms soon disappear.

But the parasite doesn't. It heads for nerve cells deep in the muscles of internal organs - usually the esophagus, colon or heart. It stays there, feeding off the nerve tissue, for years, even decades. For some people, that never causes problems.

In about one-third of cases, the nerve damage eventually begins to show. Swallowing becomes painful. Or the colon stops working. Or, most often, the heart stops beating in sync, enlarges and fails.

It's the long incubation period that makes Chagas a particular threat to the blood supply. Because decades may pass without symptoms, people may immigrate and become blood donors in the United States without knowing they are infected.

The long incubation also means it's likely there are more people already infected from U.S. blood transfusions who don't know it.

"I think everybody recognizes you can't detect every single one," Kleinman said.

But Kleinman doubts there are an epidemic of unrecognized infections, because many people who need blood have weakened immune systems. In those people, the disease shows up quickly, and there hasn't been a rash of cases.

People shouldn't be afraid of getting Chagas from a transfusion now, he stressed.

"It's an extremely unlikely outcome of any transfusion," he said. "The risk is in the many millions."

The test Leparc is working on would be similar to other tests now done on donated blood now. It wouldn't look for the parasite itself, but try to detect antibodies that the donor's immune system has formed to try to fend off the disease.

Leparc's trials will help show which substances react best to the antibodies and assess the accuracy of the test. If it misses cases, infected blood could reach donors. But if it mistakenly identifies blood as positive, that could result in throwing away good blood and needlessly worrying healthy donors.

Leparc and Kleinman expect that once a test is developed, the FDA will require its use on donated blood, which already is tested for eight different diseases, from HIV to hepatitis to West Nile virus. FDA blood experts have had several meetings to discuss test development, and say the risk of Chagas-infected donors is rising.

"We certainly encourage manufacturers to develop tests," said Lenore Gelb, FDA spokeswoman. "We would certainly consider recommending donor screening, provided a suitable test were available."

Testing won't be cheap - especially when weighed against the number of people likely to be infected. Consider that the chance of infection is relatively rare, and the lengthy incubation period. Then estimate that testing would add $1 to $5 to each one of the 14-million units of blood donated in the United States each year, Kleinman said.

"When you add it all up, you're spending a lot of money in the system, and preventing just a few infections," he said.

Will it be worth it?

"That's just a reality," Kleinman said. "We think the public expects blood to be as safe as it can possibly be."

Caused by a parasite

Spread by the triatomine bug indigenous to Central and South America

Infects as many as 18-million people worldwide

Kills about 50,000 people a year

Parasite feeds on nerve tissue of organs such as esophagus, colon or heart, often for years without symptoms. Eventually, damage can show, including painful swallowing or heart failure

Can be transmitted through blood transfusions, but few cases have been documented.