posted
(So where are the tests for lyme, babesia, etc?)
December 13, 2006
F.D.A. Approves Test for Fatal Parasitic Infection
By DONALD G. McNEIL Jr.
After years of delays, the Food and Drug Administration approved a test today for a fatal parasitic infection that is common in Latin America and increasingly prevalent in the United States blood supply.
The nation's major blood banks said they would quickly adopt the test for Chagas disease, which in Latin America is usually transmitted by the bite of a parasite-carrying insect called the kissing bug, but can also be passed from mother to child or through blood transfusion or organ donation.
About 100,000 people in the United States are thought to be infected with Chagas. The American Red Cross estimated that in the Los Angeles area, the chance of getting a unit of potentially infected blood is 1 in 2,000, up from 1 in 10,000 estimated a decade ago.
Not all units of blood that test positive for antibodies to the Chagas parasite can actually transmit the disease, a Red Cross scientist said, but since it is impossible to tell which ones can and which cannot, all blood that tests positive must be discarded, a Red Cross scientist said.
The announcement today that a test made by Ortho-Clinical Diagnostics, a Johnson & Johnson subsidiary, had been approved is ``great news,'' said Dr. Stuart J. Kahn, a Chagas expert at the Infectious Disease Research Institute in Seattle who is not involved in the competing efforts to create tests for the disease.
``And it's certainly a bit overdue,'' he added. ``People have been waiting for this for a while now.''
Besides protecting the blood supply, the tests will also give a more accurate idea of the extent of Chagas infectiun in the United States. The numbers are assumed to be increasing rapidly as a result of immigration from the region where it is common, ranging from southern Mexico to northern Argentina. Up to 20 million people there are believed to be infected.
As for the United States, ``the 100,000 figure is a rough estimate, but we really don't know,'' said Dr. James H. Maguire, a former chief of parasitic diseases at the federal Centers for Disease Control and Prevention. ``Most people don't know they're infected.''
Discovering new cases will pose a quandary for doctors and patients, because there is not yet any official C.D.C. guidance on what to tell people who are infected but appear to be healthy.
The only treatments are two drugs, nifurtimox and benznidazole, that cause very unpleasant side effects. They cure up to 95 percent of recently infected children, according to Dr. Louis V. Kirchhoff, a leading Chagas expert at the University of Iowa, but they are successful in fewer than 10 percent of adults with long-dormant infections. Complicating matters, it is nearly impossible to tell when treatment of such patients has worked. because the antibodies detected by the test linger in the blood.
The course of Chagas infection is mysterious. Only about 1 percent of those infected show any immediate symptoms, which can include fever, malaise and swelling. Most patients appear to recover, although a few infants and people with suppressed immune systems suffer fatal brain swelling.
The greater threat comes later: 10 to 25 percent of all those infected develop a dormant form of the disease that lingers in the nerve cells of the heart and gut for 10 to 30 years without causing symptoms, and then kills suddenly from heart failure or a ruptured intestine.
Blood banks have wanted an accurate, affordable Chagas test since 1988, when the first two cases were recorded of the disease being passed by blood donors in the United States.
``We're in favor of anything that improves the safety of the blood supply,'' said Jennifer Garfinkel, a spokeswoman for the American Association of Blood Banks.
But because there have been few known cases here, experts said, there was little pressure on the Food and Drug Administration to ask for a test or on the diagnostics industry to develop one.
Only 12 cases of the disease are known to have been transmitted in the United States or Canada, seven by blood donation and five by organ transplant.
Meanwhile, tests for other diseases, including West Nile Fever and SARS, were more urgent, and the agency did not officially invite manufacturers to submit Chagas tests until 2002.
But data gathered in the late 1990s made it clear that the problem was rapidly growing worse.
With the test now available, the next step will be for the C.D.C. to decide what advice to give to people who come up positive.
Chagas experts from North and South America agree that children should be treated with the drugs, Dr. Kirchhoff said. (Children do not donate blood, but would be tested if their mothers test positive.)
Older patients should be checked by cardiologists for signs of incipient heart disease. But there is too little data, he said, to know with certainty when to treat symptom-free adults.
Both drugs are available only through the C.D.C. Nifurtimox must be taken for up to four months, and can cause serious stomach upset, tics and even seizures. Benznidazole must be taken for two months, and it can cause severe rashes and weaken the immune system.
Copyright 2006 The New York Times Company
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