Beware Beetle Kiss Of Death

Parasite A Threat To Blood Supply

January 28, 1995|By Laurie Goering, Tribune Staff Writer.

RIO DE JANEIRO — First it was killer bees, fire ants and Asian tiger mosquitoes. Now comes the kissing beetle.

The triatomine beetle that carries Chagas disease, the scourge of Latin America, prefers to kiss its victims on the face.

At night it crawls out of its hiding place in an adobe wall or thatched roof and searches for a meal of human blood. It prefers to bite near the eyes, first injecting an anesthetic to ensure the victim doesn't awaken.

FOR THE RECORD - Additional material published Feb. 2, 1995:
Corrections and clarifications.
A Page 1 article Saturday incorrectly referred to the carrier of Chagas disease as the triatomine beetle. It is not a beetle, but a Hemiptera, or true bug. The Tribune regrets the error.

The beetle drinks until it is gorged. And then, before crawling away, it defecates in the tiny wound, leaving behind in the victim's blood deadly and untreatable protozoa that can kill-though sometimes not until 20 years later.

"The bite is completely painless. You don't feel anything," said Rio biologist Patricia de Azambuja, tapping a glass jar that held one of the nearly inchlong, black-brown beetles in her laboratory. "Sometimes you have no immediate symptoms at all."

Little known in the U.S., Chagas is the most costly and deadly tropical disease in Latin America, according to the World Health Organization. Worldwide it ranks third, behind only malaria and schistosomiasis, a disabling disease caused by microscopic flukes.

Chagas kills 45,000 people a year throughout Latin America, including some who have no memory of being bitten and no symptoms at all until the day they mysteriously collapse with heart failure.

The Trypanosoma cruzi protozoa that cause Chagas work by subverting the body's immune system. They instruct protective white blood cells to commit suicide and turn other defenses against the body's own cells, producing longstanding inflammation that eventually leads to hardening and lesions in the heart and intestines.

In about a third of all cases, the damage is so great the victim eventually dies, or requires a pacemaker, heart transplant or other costly surgery. Pacemakers and surgery for Chagas victims alone cost $250 million in Brazil in 1987, the latest year for which figures are available.

"It's very, very expensive," said De Azambuja, who has seen two of her laboratory workers stricken with the disease after lab accidents.

Charles Darwin, the British naturalist who developed the theory of natural selection while on a voyage around South America in the 1830s, wrote in his journals of an exotic South American beetle that drank blood.

Long a disease among the rural poor, Chagas has in recent years moved into Latin America's cities as well, brought by campesinos searching for jobs and an escape from oppressing poverty.

The sickness also has reached into the region's blood supply, infecting an estimated 10,000 Brazilians a year and threatening thousands of other Latin Americans who live far from the reach of the so-called "kissing beetle."

So far, killer bees, fire ants and Asian tiger mosquitoes haven't lived up to the dire warnings that they would wreak havoc in the U.S.

But the U.S. blood supply potentially is at risk from the kissing beetle as more migrants and travelers pass between the U.S. and Latin America, researchers say. And mutations in the triatomine beetle itself could mean the bug-which already lives in the U.S.-could begin infecting humans north of the border.

"People have to remember this disease isn't just in South America. It's in Central America (and Mexico) as well. And the beetles are already here," said Jose Ribeiro, a Brazilian-born entomologist at the University of Arizona in Tucson.

In the United States, the triatomine beetle lives mainly in wooded areas of the South, where it bites forest animals, including opposums and pack rats. Some of the beetles carry the deadly Chagas protozoa and transmit them to animals.

But few of the U.S. beetles bite human beings. And even those that do fail to pass along the protozoa because these beetles wait at least 15 minutes after feeding to defecate, usually after they're long gone from the wound, De Azambuja said.

That so far has kept Chagas from becoming a problem in the U.S. But with more and more families choosing to live in wooded suburban environments, Ribeiro believes any small change in the beetle's behavior has the potential to turn Chagas into a crisis for the U.S.

"If you have all the players it's just a matter of time," he suggested, noting that he's found triatomine beetles that bite humans even in his son's bedroom in Tucson.

But the greater risk is to the U.S. blood supply, researchers say. At least 100,000 to 370,000 Latin American migrants who carry the Chagas protozoa now live in the U.S., according to WHO estimates. And three fatal cases of Chagas infection recently were reported in the U.S. and Canada, all from transfusions.

So far, the U.S. doesn't test its blood supply for Chagas disease, according to the World Health Organization.

Still, the problem is tiny in the U.S. compared to Latin America, where 18 million people, from Mexico to the southern tip of Argentina, are infested with the parasite. Half of those stricken live in Brazil.