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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.

Courtesy of the Oswaldo Cruz Ins

titute

Carlos Ribeiro Justiniano das Chagas

Her name is Maria Luiza Alves Ferreiraand she was born on a cattle arm inMinas Gerais, south-eastern Brazilin 1949. She had nine siblings at theoutset. And then there were three. “Ilost six brothers to Chagas disease,” shesays matter-o-actly. “Tey all died in ashort period o time.” What killed themwas a parasite carried by a blood suck-ing insect, the reduviid bug. Forty yearsbeore Maria Luiza was born, Brazilianphysician Carlos Ribeiro Justiniano das

Chagas, who had been brought up ona arm just like hers, had identied theparasite and what it did.

Chagas stands alone in the annalso tropical medicine as the only re-searcher ever to describe a new inectiousdisease in all its aspects, rom the causalpathogen, the vector – the blood-suckingtriatomine bug that transmits it – andthe parasite’s lie-cycle with its naturalreservoirs to a description o the diseaseitsel. In 1908, he discovered the parasiteand then, in the ollowing year, while

observing blood samples rom a two-year-old girl, he identied the pathogeninecting her as the same fagellateprotozoan. Tis parasite, he ound, wascarried in the gut o a bug known in theAmericas by several names, notably ‘thebarber’ and ‘the kissing bug’ because itbites the ace o its sleeping victims.

Chagas mistakenly thought thatthe triatomine bug’s bite was the mainroute o inection. ransmission, in act,occurs via the insect’s aeces, as the bugsdeecate on a person’s skin while eedingon their blood. But his achievement stillstands. Identiying the pathogen as anew species o Trypanosoma, he namedit Trypanosoma cruzi, abbreviated toT. cruzi, ater Oswaldo Cruz, the greatBrazilian scientist – his mentor andboss. “Te discovery caused a consider-able stir in the Brazilian scientic com-

munity,” says historian Simone Krop o the Oswaldo Cruz Foundation, notingthat the National Academy o Medicinetook the unprecedented step o creatinga new membership position to inviteChagas into its ranks in 1910.

While Brazil’sscientic community celebrated Chagas’sachievement, they were also orced totake stock o the

precarious sanitary and living conditionsexperienced by many o their countrymenin rural areas.

Simone Kropf 

Usually, people who have been bit-

ten become inected when the triato-mine bug’s aeces enter the insect bite,or when they rub their eyes or throughbreaks or cuts in the skin. But T. cruzi  can also be transmitted through bloodtransusions, contaminated ood anddrink, congenitally – when babies areborn to inected mothers – and eventhrough organ transplants. Te acutephase o the disease lasts around twomonths and is usually asymptomatic.Tat is ollowed by the chronic phasethat will last a lietime without treat-

ment. Some 30% o cases can lead toheart disease, while 5–10% o cases takeon a digestive or mixed orm, combin-

“While Brazil’s scientic commu-

nity celebrated Chagas’s achievement,they were also orced to take stock o the precarious sanitary and livingconditions experienced by many o their countrymen in rural areas,” saysKrop, who notes that the disease wasand still is closely associated with pov-erty. According to the Pan AmericanHealth Organization, WHO’s regionaloce in the Americas, most peopleaected by Chagas today come romlow-income groups living in poorly constructed houses. In their natural

state, the bugs that transmit the parasitelive in palm trees and rock crevices, butsome have adapted to lie in humandwellings, typically hiding during theday in the cracked walls o mud ormud-brick houses, and coming out atnight to eed.

It is estimated that about 10 mil-lion people are inected with Chagasin the Americas, 2 million o them inBrazil alone. More than 10 000 dieeach year as a result. Because Chagasdisease aects mainly poor people in

developing countries, little has beeninvested in diagnostics and treatment –despite intensive research on the disease.But in the last ew years several researchprojects have taken up the challenge.

Te Special Programme orResearch and raining in ropicalDiseases, which is sponsored by WHOand other United Nations agencies, issupporting three projects involving new drug and diagnostics development orChagas. One is a clinical trial in col-laboration with the Canadian Institutes

o Health Research to examine the roleo trypanocidal treatment in individualsin the chronic phase o asymptomatic

Courtesy of José Rodrigues Coura

José Rodrigues Coura, a researcher at the Oswaldo

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José Pantoja

Researcher André Luiz Rodrigues Roque (ront right) and his colleagues working at a mobile laboratory that

investigates outbreaks o Chagas in the feld.

Other research is going on, in-cluding projects in Argentina, Brazil,Canada, Colombia, France and theUnited States [o America], some o this supported by the Drugs or Ne-glected Diseases initiative. Tere is also

aT. cruzi 

genome project run by theSeattle Biomedical Research Institutein the USA and the Karolinska Insti-tute in Sweden.

“It is a disgrace that we haveknown about Chagas or 100 years andyet most people in need still do nothave access to diagnosis and treat-ment,” says Dr Pedro Albajar Vinas, atechnical ofcer rom the departmento Neglected ropical Diseases at theWorld Health Organization (WHO)in Geneva. “But with renewed com-

mitment rom countries in the Ameri-cas, Europe and the Western Pacic,we hope this will change.”

Countries most aected by thedisease are working together to controlChagas in other ways too, notably with intergovernmental initiatives.Te Southern Cone Initiative is one;launched in 1991, it brings togetherthe ministers o health o Argentina,the Plurinational State o Bolivia,Brazil, Chile, Paraguay and Uruguay.Since then, Argentina, Brazil, Chile

and Uruguay have made considerableprogress in reducing transmission o the disease. João Carlos Pinto Dias,a researcher rom the René RachouInstitute in the Brazilian city o MinasGerais, says that vectoral and transu-sion transmission o Chagas diseasein large areas o the country has beendramatically reduced. “Te incidenceo new cases reported annually was100 000 per year in the 1970s. oday,the country sees around 100 to 150cases per year and most o those are the

result o oral transmission in the Ama-zon region,” he says, adding; “But wecannot orget the millions o chroniccases, they are still a challenge.”

WHO’s Member States committedthemselves to halting transmission o Chagas by 2010 in a resolution at theWorld Health Assembly in 1998 – agoal they will not achieve. Te challeng-es are great. T. cruzi is a moving targetand does not limit itsel to triatominebugs but has multiple animal reservoirs.Moreover, as habitats change so do theparasite’s opportunities or coloniza-tion. André Luiz Rodrigues Roque, a re-

h h ith hi ll h t

up mobile laboratories in the Brazilianstates o Santa Catarina, ocantins, Paráand Ceará, spends a good deal o timeinvestigating outbreaks in the eld. Hehas observed that deorestation and areduction o auna diversity can lead toanimals with high T. cruzi parasite loadsin their blood. “Te Amazon region isa mosaic,” Roque says. “Tis means wecannot take only one action to ghtthe disease, because there are dierenthabitats and dierent epidemiologicalproles.”

Te incidenceo new cases

reported annually was 100 000 per

year in the 1970s.oday, the country sees around 100 to150 cases per yearand most o those

are the result o oraltransmission in theAmazon region.

João Carlos Pinto Dias 

In recent years rapid jet travel andmigration o populations has led to theimportation o Chagas into countries

id L i A i i l di A

tralia, Canada, France, Germany, Italy,Japan, Spain and the USA.

For José Rodrigues Coura, a re-searcher at the Oswaldo Cruz Institutein Rio de Janeiro, nothing less than“constant vigilance” is needed to dealwith Chagas disease – a relentlessattack on all ronts including: vectorcontrol, in so ar as this is possible;housing improvement; the provision o comprehensive and accessible medicalcare; blood-screening programmes,and the treatment o already inectedindividuals. “It is a disease that oc-curred or thousands o years and itwill occur or another thousand,” saysCoura. While eradication cannot beconsidered, there is hope or haltingtransmission.

Ater all, the past 40 years or sohave seen signicant progress, and thereare now some promising developmentsin terms o new diagnostics and treat-ment. WHO’s Albajar Vinas is lookingorward to 2010, when countries areset to re-afrm their commitment tocontrolling Chagas in a resolution at theWorld Health Assembly. Te resolu-tion, originally scheduled or this year’sassembly, was postponed until nextyear. “We have a better understandingo how to treat and manage Chagasdisease. We know that using the present

tools we can control the disease in mostplaces in the world,” he says. “We needthis commitment to maximize the use h l l d h ” ■

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