Posted on 02/15/2009 10:07:35 AM PST by SwinneySwitch
For a disease that begins with a bite from the deceptively sweet-sounding kissing bug, Chagas disease is a major killer in some parts of the world.
The bug deposits a parasite that can lurk silently in the body for decades before causing the heart to enlarge — and sometimes the colon or esophagus as well.
Chagas, which afflicts millions in Latin America, was long thought to be largely confined there. But a recently approved test to screen blood donors has identified hundreds of cases across the United States — including eight in Bexar County.
The sudden appearance of these cases has taken some health officials by surprise. And although many of these patients may prove to be immigrants who brought the disease into the United States — or their children, since it can be passed from mother to child — experts believe some were infected in this country.
With new information from the blood banks, they hope to get a better idea of how many. Few here ever are tested for Chagas (pronounced SHAH-gus), even those diagnosed with the classic symptoms.
The Chagas parasite,Trypanosoma cruzi, is passed to humans by kissing bugs, or triatomine insects, which are common throughout the U.S. South. Texas has more types of kissing bugs than any other state, and studies have shown many of the local bugs carry the parasite.
Outbreaks have been discovered in working dogs at Lackland AFB and research primates at Southwest Foundation for Biomedical Research.
“The question is, if the bug is here, ifT. cruzi is here, if animals are getting infected — are humans?” asked Roger Sanchez, senior epidemiologist with the Metropolitan Health District, who has launched the local investigation.
Area health officials have begun the job of tracking down donors who tested positive to interview them about their travel histories and risk factors. A federal investigation is similarly under way nationwide.
“Here at CDC, we're trying to identify how people are getting infected in the U.S.,” said Dr. Susan Montgomery with the parasitic diseases branch of the Centers for Disease Control and Prevention. “Are there activities they are engaging in where they come in contact with infected wildlife or the infected bugs (through) camping or hunting?”
E.J. Hanford, professor of environmental science at Collin County Community College in Frisco who has co-authored papers on Chagas, estimates that perhaps 200,000 immigrants in the United States could have chronic Chagas disease — most of them likely unaware — based on known infection rates and patterns throughout the hemisphere.
Montgomery said it's important for doctors in places like South Texas to consider Chagas disease when they see a heart patient who might fit the profile. Until recently, she and others said, Chagas has been mostly off the medical community's radar screen.
Not-so-polite bugs
The particulars of Chagas aren't for the weak of stomach. The teardrop-shaped bugs, 1 to 11/2 inches long and rimmed with a dozen orange spots, feed on blood — often at night.
After eating, they excrete the parasite through feces. If they deposit it immediately after eating, which is typical, the unwary victim can scratch at the bite and rub the parasites into the open wound.
Some experts think the U.S. bugs are more “polite,” as one put it, than their Latin American cousins, waiting to relieve themselves until they are well away from their victims. And that politeness might be why locally acquired infections seemed to be rare here.
But more recent research, Montgomery said, is dispelling the idea that our bugs are so polite. If infections here are rare — and not just unrecognized — it's more likely that it's because of better housing and sanitation.
The infection also can be passed through blood and organs from an infected donor, or by eating food contaminated by the parasites.
Not everyone infected goes on to develop the disease. Some become sick shortly after infection, sometimes with telltale swelling around the eye known as Romaña's sign. Others just carry the infection silently, often for decades, until they die from a sudden heart attack or develop chronic symptoms including a particular heart arrhythmia.
Dr. Pablo Okhuysen, professor of internal medicine at the University of Texas Health Science Center at Houston, who diagnosed a fatal case of Chagas in a female patient a few years ago, said even family doctors should be aware of the disease — particularly as blood banks now are notifying infected donors and telling them to seek medical attention.
Only two drugs are available to treat Chagas, and neither is approved in the United States. They are available only through the CDC on a compassionate basis. Both are fairly toxic, and there is controversy about how effective they are in the later stages of disease.
Treatment works best early in the infection, particularly in children.
Sarah Williams-Blangero, chairwoman of genetics at Southwest Foundation for Biomedical Research, has been studying Chagas in a rural village in Brazil for several years. She's found genetic differences between people that might determine who is more likely to become chronically infected.
“It is a devastating disease for these families. And of course it impacts whole families. And everybody has a story about some son or cousin or nephew who dropped dead in the fields at a relatively young age because they have this disease.”
Testing the blood
The Food and Drug Administration approved the Chagas test for blood banks at the end of 2006. The South Texas Blood and Tissue Center began using the test on platelet donors in August 2007. None of those donors tested positive.
At the beginning of 2008, the blood bank began screening all first-time donors who'd never been tested before. Over about a year, it screened 84,366 units of whole blood and found 26 infected donors among the 43 South Texas counties it serves. Eight were in Bexar County, ranging in age from 18 to 53.
Dr. Norman Kalmin, president and CEO of the blood bank, said the organization's medical advisory board has recommended a conservative approach with the new Chagas test, which at $7 per unit is twice as expensive as the next most costly test. A second manufacturer is expected to offer a test soon, which could lower the cost.
The test is voluntary and some blood banks don't perform it at all, while others test every unit of blood every time.
Still, most do some testing and so far, 782 confirmed positives have been found nationwide since the beginning of 2007, according to the American Association of Blood Banks. The largest clusters of infection have been in Texas, California and Florida, with a few large pockets in the Northeast.
The local health department, with the help of others in the region, is sending letters to those 26 donors as a first step in interviewing them to learn whether they might have acquired the infection outside the country or here.
“I think the most important message is, the blood supply in the U.S. is now even safer,” the CDC's Montgomery said. “It's probably the safest blood supply in the world. But with the introduction of screening forT. cruzi, we've made it even safer.”
Dr. Paul Southern, professor of pathology at UT Southwestern Medical Center in Dallas, who has studied Chagas in Belize, thinks that all blood should be screened and all human cases reported. As of now, veterinarians are required to report a diagnosis of Chagas in dogs. Only Arizona requires that human cases be reported to authorities.
“Physicians in general — other than a few — never even think about this disease,” Southern said. “It's not a part of their consciousness. They could see a kid with a swollen eye who said a bug bit him and not think about Chagas disease. That's one of the main impediments to recognition.”
Consider donating.
Cheers!
Ping!
If you want on, or off this S. Texas/Mexico ping list, please FReepMail me.
Thank you President Bush and all illegal aliens everywhere.
“E.J. Hanford, professor of environmental science at Collin County Community College in Frisco who has co-authored papers on Chagas, estimates that perhaps 200,000 immigrants in the United States could have chronic Chagas disease — most of them likely unaware — based on known infection rates and patterns throughout the hemisphere.”
Lovely, just lovely...
Is the “kissing bug” the same as the “assassin bug”?
I’ve said for years that “war” will not be the next downfall of the earth........it will be disease, epidemics, virii, etc. We’re already deeper in that direction than we even realize.
Creepy.
It is a real nasty disease...named after the Brazilian doctor who identified it. I worked in South America for 8-years and we had Chagas warning signs at our remote camp sites. Scary one.
The drugs! What are the drugs! Some can get them in Latin America if they only knew WHICH drugs. Thanks in advance.
Is one of them chloranphenicol?
Prevention would be the best way of curing it, but too bad we cant spray DDT because of the bunny huggers love of animals over people.
Immigrants just bringing in disease Americans don’t want to bring (or, actually, just don’t want).
I think they are referring to Benznidazole and nifurtimox.
Gee whiz! I used to play outside in the grass and would get those chiggas all over! Itched like the devil, but kerosene would usually quiet them down.
Oh. Chagas? Don’t know nothin’ about no chagas. Chiggas is what we had.
Another nasty bug disease.
Ping!
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