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Chagas: one hundred years later

This April marked the 100th anniversary of Carlos Chagas’s discovery of a new disease. Yet most people in need still lack access to diagnosis and treatment. Claudia Jurberg reports.

Her name is Maria Luiza Alves Ferreira Chagas mistakenly thought that and she was born on a cattle farm in the triatomine bug’s bite was the main Minas Gerais, south-eastern Brazil route of infection. Transmission, in fact, in 1949. She had nine siblings at the occurs via the insect’s faeces, as the bugs outset. And then there were three. “I defecate on a person’s skin while feeding lost six brothers to Chagas disease,” she on their blood. But his achievement still says matter-of-factly. “They all died in a stands. Identifying the pathogen as a Courtesy of the Oswaldo Cruz Institute short period of time.” What killed them new species of Trypanosoma, he named was a parasite carried by a blood suck- it Trypanosoma cruzi, abbreviated to ing insect, the reduviid bug. Forty years T. cruzi, after Oswaldo Cruz, the great Carlos Ribeiro Justiniano das Chagas before Maria Luiza was born, Brazilian Brazilian scientist – his mentor and boss. “The discovery caused a consider- physician Carlos Ribeiro Justiniano das “While Brazil’s scientific commu- Chagas, who had been brought up on able stir in the Brazilian scientific com- munity,” says historian Simone Kropf of nity celebrated Chagas’s achievement, a farm just like hers, had identified the they were also forced to take stock parasite and what it did. the Oswaldo Cruz Foundation, noting that the National Academy of Medicine of the precarious sanitary and living Chagas stands alone in the annals took the unprecedented step of creating conditions experienced by many of of tropical medicine as the only re- a new membership position to invite their countrymen in rural areas,” says searcher ever to describe a new infectious Chagas into its ranks in 1910. Kropf, who notes that the disease was disease in all its aspects, from the causal and still is closely associated with pov- pathogen, the vector – the blood-sucking erty. According to the Pan American triatomine bug that transmits it – and Health Organization, WHO’s regional the parasite’s life-cycle with its natural While Brazil’s office in the Americas, most people reservoirs to a description of the disease scientific community affected by Chagas today come from itself. In 1908, he discovered the parasite celebrated Chagas’s low-income groups living in poorly and then, in the following year, while achievement, they constructed houses. In their natural observing blood samples from a two- state, the bugs that transmit the parasite year-old girl, he identified the pathogen were also forced to live in palm trees and rock crevices, but infecting her as the same flagellate take stock of the some have adapted to life in human protozoan. This parasite, he found, was precarious sanitary dwellings, typically hiding during the carried in the gut of a bug known in the and living conditions day in the cracked walls of mud or Americas by several names, notably ‘the mud-brick houses, and coming out at experienced by many night to feed. barber’ and ‘the kissing bug’ because it of their countrymen bites the face of its sleeping victims. It is estimated that about 10 mil- in rural areas. lion people are infected with Chagas Simone Kropf in the Americas, 2 million of them in Brazil alone. More than 10 000 die each year as a result. Because Chagas Usually, people who have been bit- disease affects mainly poor people in ten become infected when the triato- developing countries, little has been mine bug’s faeces enter the insect bite, invested in diagnostics and treatment – or when they rub their eyes or through despite intensive research on the disease. breaks or cuts in the skin. But T. cruzi But in the last few years several research can also be transmitted through blood projects have taken up the challenge. transfusions, contaminated food and The Special Programme for drink, congenitally – when babies are Research and Training in Tropical born to infected mothers – and even Diseases, which is sponsored by WHO through organ transplants. The acute and other United Nations agencies, is phase of the disease lasts around two supporting three projects involving new months and is usually asymptomatic. drug and diagnostics development for That is followed by the chronic phase Chagas. One is a clinical trial in col- that will last a lifetime without treat- laboration with the Canadian Institutes Courtesy of José Rodrigues Coura ment. Some 30% of cases can lead to of Health Research to examine the role heart disease, while 5–10% of cases take of trypanocidal treatment in individuals José Rodrigues Coura, a researcher at the Oswaldo on a digestive or mixed form, combin- in the chronic phase of asymptomatic Cruz Institute in Rio de Janeiro, Brazil. ing heart and digestive problems. Chagas.

Bull World Health Organ 2009;87:491–492 | doi:10.2471/BLT.09.030709 491 News

Other research is going on, in- cluding projects in Argentina, Brazil, Canada, Colombia, France and the United States [of America], some of this supported by the Drugs for Ne- glected Diseases initiative. There is also a T. cruzi genome project run by the Seattle Biomedical Research Institute in the USA and the Karolinska Insti- tute in Sweden. “It is a disgrace that we have known about Chagas for 100 years and yet most people in need still do not have access to diagnosis and treat- ment,” says Dr Pedro Albajar Vinas, a technical officer from the department of Neglected Tropical Diseases at the World Health Organization (WHO) in Geneva. “But with renewed com- mitment from countries in the Ameri- José Pantoja cas, Europe and the Western Pacific, we hope this will change.” Researcher André Luiz Rodrigues Roque (front right) and his colleagues working at a mobile laboratory that Countries most affected by the investigates outbreaks of Chagas in the field. disease are working together to control Chagas in other ways too, notably up mobile laboratories in the Brazilian tralia, Canada, France, Germany, Italy, with intergovernmental initiatives. states of Santa Catarina, Tocantins, Pará Japan, Spain and the USA. The Southern Cone Initiative is one; and Ceará, spends a good deal of time For José Rodrigues Coura, a re- launched in 1991, it brings together investigating outbreaks in the field. He searcher at the Oswaldo Cruz Institute the ministers of health of Argentina, has observed that deforestation and a in Rio de Janeiro, nothing less than the Plurinational State of Bolivia, reduction of fauna diversity can lead to “constant vigilance” is needed to deal Brazil, Chile, Paraguay and Uruguay. animals with high T. cruzi parasite loads with Chagas disease – a relentless Since then, Argentina, Brazil, Chile in their blood. “The Amazon region is attack on all fronts including: vector and Uruguay have made considerable a mosaic,” Roque says. “This means we control, in so far as this is possible; progress in reducing transmission of cannot take only one action to fight housing improvement; the provision of the disease. João Carlos Pinto Dias, the disease, because there are different comprehensive and accessible medical a researcher from the René Rachou habitats and different epidemiological care; blood-screening programmes, Institute in the Brazilian city of Minas profiles.” and the treatment of already infected Gerais, says that vectoral and transfu- individuals. “It is a disease that oc- sion transmission of Chagas disease curred for thousands of years and it in large areas of the country has been will occur for another thousand,” says dramatically reduced. “The incidence The incidence Coura. While eradication cannot be of new cases reported annually was of new cases considered, there is hope for halting 100 000 per year in the 1970s. Today, reported annually transmission. the country sees around 100 to 150 was 100 000 per After all, the past 40 years or so cases per year and most of those are the have seen significant progress, and there result of oral transmission in the Ama- year in the 1970s. are now some promising developments zon region,” he says, adding; “But we Today, the country in terms of new diagnostics and treat- cannot forget the millions of chronic sees around 100 to ment. WHO’s Albajar Vinas is looking cases, they are still a challenge.” 150 cases per year forward to 2010, when countries are WHO’s Member States committed and most of those set to re-affirm their commitment to themselves to halting transmission of controlling Chagas in a resolution at the Chagas by 2010 in a resolution at the are the result of oral World Health Assembly. The resolu- World Health Assembly in 1998 – a transmission in the tion, originally scheduled for this year’s goal they will not achieve. The challeng- Amazon region. assembly, was postponed until next es are great. T. cruzi is a moving target João Carlos Pinto Dias year. “We have a better understanding and does not limit itself to triatomine of how to treat and manage Chagas bugs but has multiple animal reservoirs. disease. We know that using the present Moreover, as habitats change so do the In recent years rapid jet travel and tools we can control the disease in most parasite’s opportunities for coloniza- migration of populations has led to the places in the world,” he says. “We need tion. André Luiz Rodrigues Roque, a re- importation of Chagas into countries this commitment to maximize the use searcher who with his colleagues has set outside Latin America, including Aus- of the tools we already have.” ■

492 Bull World Health Organ 2009;87:491–492 | doi:10.2471/BLT.09.030709