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Triatoma dimidiata, the Kissing Bug
Triatoma dimidiata, the "Kissing Bug"

The Kiss of Death

by Michael L. Smith

A tan bug, a deadly disease, jungle plants, and outer space. The makings of a science fiction thriller? No. Science reality in a search to stop a killer.

In Central and South America Chagas Disease is a bigger threat than AIDS. It infects an estimated 18 million people in Latin America and kills 20,000 every year. And with cases now showing up in other parts of the world, passed through blood transfusions, it isn't a disease of just the Latin peasant anymore.

the kissing bug

The inch-long insect responsible for transmitting Chagas is called the Kissing Bug in Central America. South Americans use the name Vinchuca. To scientists it is Triatoma dimidiata. It is a common, secretive rain forest bug that lives in the trees, biting birds and jungle animals. As humans continue to cut down the forest, it is losing its natural home.

The Kissing Bug adapts well to substitute accommodations, finding suitable hiding places in the cracks and crevices of typical peasant dwellings around the rain forests. This nocturnal nemesis is an innocuous-looking insect that sucks blood, much like a mosquito does. Its habit of defecating and urinating immediately after eating, provides the Chagas parasite, which lives in the bug's feces, ready access to the prospective host's blood stream.

an ancient malady

Although first discovered in 1910 by a Brazilian doctor, anthropologists have since identified evidence of its existence in Peruvian mummies. As studies have continued, some alarming numbers concerning its range have come to light. The disease manifests itself from southern Texas all the way down through Central and South America. Data details cases in all but the heart of the Amazon. According to Boletín Chileno de Parasitología, 1989, percentages of infected people living in areas where the Chagas parasite is found range from 3% in Uruguay and 11% in Costa Rica, to 33% in Colombia and over 50% in areas of Bolivia.

The variants of Chagas, which can remain dormant or semidormant and undetected in the host for 20 years, attack the human body in three principal ways. In Costa Rica and most of Central America the parasite usually lodges in the heart muscle. When it becomes active, it begins eating the muscle. The tissue eventually becomes so thin it simply bursts from normal vascular pressure. It is believed that in regions where the bug lives, many of what are diagnosed as heart attacks, especially in younger people and among the poor, are the result of Chagas. More virulent strains in South America attack the colon and esophagus. These latter manifestations, paradoxically, have a better chance of diagnosis and can often be corrected by surgery to remove the affected parts.

Doctor Bert Kohlmann, a professor at EARTH University in Costa Rica and lead scientist in a collaborative project to develop a medicinal treatment, said that the disease is now spreading far beyond Latin America through blood donated by migrating Latin Americans who unknowingly carry the parasite. At the present time only a few South American countries screen donated blood for Chagas. North America and Europe do not check for this parasite.

back to the jungle

EARTH University opened in 1989, with the mission of providing a university-level education "in the agricultural sciences and natural resources, contributing to the sustainable development of the humid tropics." Realizing that their jungle laboratory might disappear before they could fully understand it, they felt that an ambitious curriculum of applied research would greatly benefit the university and its students.

Costa Rica's astronaut, Doctor Franklin Chang, an inspiration to Costa Ricans for many years, offered to help EARTH. Through his contacts at various institutions, a joint project team was formed to study medicinal uses of tropical plants. Two universities in Chile which were part of the team, Universidad de Santiago de Chile and Universidad Católica del Norte in Antofagasta, had been working for years to develop a cure for the deadly Chagas disease. This was a project that fit in with the tenets of EARTH, so scientists at the university started collecting plants from the tropical forests surrounding the campus and began their quest.

The parasite and its destructive ways are known. Finding a safe way to block its action is the problem. The scientists and students at EARTH discovered plant extracts that would block key enzymes in the parasite. They needed to learn exactly which agent in the extracts worked the magic and how.

Working with the Center of Macromolecular Crystallography at the University of Alabama at Birmingham, the researchers were able to grow crystals of the parasite enzymes and attempt to map their molecular structures. But crystals grown on earth are very small and slightly misshapen due to gravity. This hinders the process of learning precisely how molecules fit together, necessary knowledge in understanding how the plant protein blocks the parasite's enzyme. Franklin Chang proposed a solution.

heading for space

Crystals grown in the microgravity of space are much larger and better formed than those grown on terra firma. According to Doctor Kohlmann, these space crystals provide scientists with 40 percent more useful information. Thanks again to Franklin Chang, the extracts collected and processed in Costa Rica, highly purified in Chile and prepared in Alabama, were to be carried into space on the space shuttle where crystals would be grown.

In February, 1996, the first joint US-Latin America space experiment flew aboard mission STS-76 on the space shuttle Columbia, as part of the Commercial Protein Crystal Growth (CPCG) experiment. Scientists needed to know if the material from the parasite would grow crystals in space. The results were positive and a second batch of samples flew aboard STS-77 in May of 1996.

Comparison of crystal growth.
Size comparison of crystals grown on earth (left) and in space (right).
Photos courtesy of the Center of Macromolecular Crystallography at the University of Alabama at Birmingham.

Results of the May flight indicated that, although the crystals grew well, more time in space was needed to have sufficiently large samples for the process of x-ray mapping. The scientists, with the help of Doctor Chang, are seeking permission to grow the crystals aboard the MIR space station. If this effort succeeds, it will increase to four the number of countries directly involved in the Chagas project.

Researchers hope that after crystals from the plant extracts and the parasite enzyme are mapped, the mechanics of the molecules will be understood well enough to develop a carrier that can successfully deliver the medicine to a patient's body. The next step, which the researchers hope to begin in 1997, will be the clinical studies.

an international effort

There is little doubt in the minds of the men and women working on this project that without the cooperation of five institutions in three countries, and the enthusiastic aid of Doctor Franklin Chang, this research would be taking many more years. Chagas is considered a poor man's disease, afflicting farmers and peasants living in and around the rain forests of the Americas. Because of the relatively small numbers involved, big pharmaceutical corporations can't rationalize getting involved. International volunteers from institutions with a more idealistic view are close to finding a cure for a deadly disease by using an intelligent mix of down-to-earth natural medicine and high-flying science.

progress update

Since this article was first published in September of 1996 research has increased in scope. After the World Bank declared Chagas Disease the number one parasite problem in Latin America, efforts redoubled to find a cure for this deadly malady. Project ChagaSpace, a cooperative effort of universities and private organizations in seven countries, is now working full time to identify an enzyme blocker that can be used to kill the parasite. Along with the organizations mentioned above, the distinguished participants in ChagaSpace include Universidad Nacional and InBio, both in Costa Rica; Universidad Nacional Autónoma de Mexico; Universidad de Sao Paulo in Brazil; Universidad de la República in Uraguay; and Instituto Fatala Chaben in Buenos Aires.

The June, 1998 flight of the space shuttle Discovery on mission STS-91 included another enzyme crystal growing experiment for this group to study. And again in October, 1998, STS-95, the John Glenn Discovery Mission also included another series of crystal growing experiments related with the Chagas research.

Learn more about Earth University at their Web site: EARTH University in Costa Rica.