from the sleeping areas, but that they needed to plaster the walls. She feared that Sarah had Chagas’ disease and asked me to examine the wound from the bite. I explained that I couldn’t tell by looking at the wound, and informed her to watch for a high fever; if that occurred, she should take Sarah to a doctor for testing and treatment. Talking with a child bitten by a vinchuca whose future as a hairdresser was threatened by a parasite made the statistics of Chagas’ disease more meaningful and alarming to me.
Public health educators, in efforts to dispel friendly attitudes towards vinchucas, in a rather bizarre fashion have sponsored contests for schoolchildren to see who could bring the most bugs to school (somewhat akin to a campaign to collect discarded drug needles). Children captured vinchucas, put them in matchboxes, and brought them to the school, where they were later examined for T. cruzi infection. Obviously, this technique encouraged children to handle vinchucas despite the fact that contamination is the major route of infection and thus this campaign put them at risk. Posters and videos are a much safer pedagogical method to educate Bolivians about vinchucas as vectors of Chagas’ disease.
Figure 15. Sarah Arredondo showing where she had been bitten by a vinchuca and possibly infected with Chagas’ disease. Several thousand children die each year in Bolivia from acute Chagas’ disease. (Photograph by Joseph W. Bastien) The insect world fascinates children in part perhaps because tiny creatures are more proportionate to their size. Jose Beltran, health educator, observed that children are much quicker than adults to learn about the different species of vinchucas, many of which are beneficial. Many Bolivian children also love to see parasites through microscopes and learn about Chagas’ disease.
On the other hand, Quechua peasants in Choromoro hate vinchucas because they suffer from their annoying bites at night. These peasants in the Department of Chuquisaca, Bolivia, are accustomed to having vinchucas in their beds, with sometimes as many as thirty to forty housed within their mattresses. One complained, “All night we are taking off their heads and destroying them. We have to sleep outside the huts to escape them. Sometimes we don’t sleep all night because we have to kill vinchucas, and when they bite us, we scratch it.”
Some Bolivians are allergic to vinchuca bites, which then result in festering sores (see Figure 16). Others vigorously scratch the itching bite, opening the skin and rubbing infected fecal matter into the wound. T. cruzi travel to the opening or are aided when the victim scratches the wound, frequently damaging the skin or pushing the parasites into the wound.
Vinchucas are not fast-flying insects like mosquitoes or flies; they only glide by means of poorly developed wings. The wings of triatomines move slowly and arduously and can barely, if at all, lift them upward, unless they are first descending from a perch. Brazilian scientists photographed the flight of these bugs with a low-light-sensitive camera. Triatomines take off from window ledges and ceilings and descend, riding air waves back and forth in large sweeping movements until they alight on their victims. Although they prefer to stay in one house, they can glide up to 1,000 meters, enabling them to travel from house to house in search of blood meals. Radar-like detectors, the two long antennae on their heads, are sensitive to carbon dioxide respiration and guide the triatomines to the exposed and heat-emitting areas of warm-blooded animals.
Compensating for being poor flyers, vinchucas are excellent crawlers, with six long and strong legs. After a blood meal, vinchucas return to their nests, literally like tankers, trailing blood and fecal matter across bedding, tables, floors, walls, and ceilings. Their tracks contaminate food and clothing, as does their fecal matter dropped from the ceiling.
As ugly as these trailing streaks are, they do provide warning signs to wary travelers wishing to spend the night in some unfamiliar room. Wary Bolivians check rooms thoroughly with flashlights and ask if and when the house and rooms have been sprayed for vinchucas. Tiny white eggs and brown blotches on the walls provide evidence that the guest will not spend the night alone. Nor does mosquito netting provide protection against the bugs’ instar stages, which are the size of fleas, from crawling underneath the netting. Vinchucas can live and reproduce for weeks with one blood meal; they remain content until their energy runs low, at which time they begin to look for another blood meal.
Figure 16. Infected bites from Triatoma infestans (vinchucas). (Photograph by staff of Proyecto Cardenal Maurer) 
Figure 17. Vinchuca and stages of T. cruzi. Vinchucas (Triatoma infestans) deposit metacyclic trypomastigotes in their feces that are infective to humans (as well as other mammals) and temporarily enter the blood. They enter tissues where they become amastigotes, then divide into other amastigotes and short, stumpy trypomastigotes that reenter the blood. These trypomastigotes are ingested by uninfected and infected vinchucas, where they transform into epimastigotes and then metacylic trypomastigotes. (From Franklin Neva and Harold Brown, Basic Clinical Parasitology, p. 66) (See Appendix 1.) Contamination through the Feces
Contamination through the bugs’ feces is the major mechanism by which T. cruzi passes from vinchucas to humans. T. cruzi transforms from a trypomastigote to an epimastigote to a metacyclic trypomastigote inside vinchucas (see Figure 17). When infected vinchucas take a blood meal, they usually defecate and deposit a metacyclic trypomastigote, which is found in the insect’s intestines, onto the victim’s skin. Metacyclic trypanosomes (tryps) travel from the feces and enter through the bite site, the eye, or other abraded skin. People often scratch the wound and rub parasites into the skin. Metacyclic tryps circulate for a short while in the blood, then enter neuron cells and become encysted as amastigotes. Amastigotes reproduce tryps that enter the blood, where they can be picked up by a vinchuca during its blood meal. (Because T. cruzi is such an infectious parasite, some laboratories in the United States do not experiment with it).
Not all species defecate at the same rate: Rhodniusprolixus and Panstrongylus megistus defecate at a great rate, while Triatoma infestans defecates at only 30 percent of that rate, and Triatoma sordida at only 10 percent (Calvo et al. 1978:70-81). Those species that defecate closest to the injection wound are the most infectious; consequently, T. infestans is most dangerous to humans and most adaptive for T. cruzi, being a very effective vector in transmitting this parasite to hosts. The longer T. cruzi is outside the vector and host, the more vulnerable it is to being lysed, or disintegrating. Children are easily contaminated with the feces of vinchucas. Babies and infants spend considerable time within and around the house, sometimes with little clothing, and they are defenseless victims for vinchucas to feed upon.
Infection through Blood Transfusions
Blood transfusion is the second most important mechanism of transmission of Chagas’ disease. Blood transfusions have enabled T. cruzi to travel beyond tropical and semitropical zones, where it was environmentally limited by the fact that its triatomine vectors needed the warmth and humidity of these areas. This makes Chagas’ disease a worldwide problem, because Latin American countries have been
