Chagas

Seminar

Chagas disease
Anis Rassi Jr, Anis Rassi, José Antonio Marin-Neto
Lancet 2010; 375: 1388–402 Division of Cardiology, Anis Rassi Hospital, Goiânia, GO, Brazil (A Rassi Jr MD, Prof A Rassi MD); and Division of Cardiology, Department of Internal Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil (Prof J A Marin-Neto MD) Correspondence to: DrAnis Rassi Jr, Anis Rassi Hospital, Avenida José Alves 453, Setor Oeste, Goiânia GO, Brazil, CEP 74110-020 arassijr@terra.com.br

Chagas disease is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi, and was discovered in 1909. The disease affects about 8 million people in Latin America, of whom 30–40% either have or will develop cardiomyopathy, digestivemegasyndromes, or both. In the past three decades, the control and management of Chagas disease has undergone several improvements. Large-scale vector control programmes and screening of blood donors have reduced disease incidence and prevalence. Although more effective trypanocidal drugs are needed, treatment with benznidazole (or nifurtimox) is reasonably safe and effective, and is now recommended for awidened range of patients. Improved models for risk stratification are available, and certain guided treatments could halt or reverse disease progression. By contrast, some challenges remain: Chagas disease is becoming an emerging health problem in non-endemic areas because of growing population movements; early detection and treatment of asymptomatic individuals are underused; and the potentialbenefits of novel therapies (eg, implantable cardioverter defibrillators) need assessment in prospective randomised trials.

Introduction
Recognised by WHO as one of the world’s 13 most neglected tropical diseases,1 Chagas disease has been a scourge to humanity since antiquity, and continues to be a relevant social and economic problem in many Latin American countries.2,3 This lifelong infection, alsoknown as American trypanosomiasis, is caused by the protozoan parasite Trypanosoma cruzi, and was discovered in 1909 by the Brazilian physician Carlos Chagas (1879–1934). Chagas’ original report4 is unique in the history of medicine, in the sense that a single scientist described in great detail both the cycle of transmission (vector, hosts, and a novel infectious organism) and the acute clinicalmanifestations of the first human case. Findings from paleoparasitology studies that recovered T cruzi DNA from human mummies showed that Chagas disease afflicted man as early as 9000 years ago.5 Notably, the first reported case of Chagas disease might have preceded Carlos Chagas’ discovery— Charles Darwin quite possibly contracted T cruzi infection during his expedition to South America in 1835, assuggested by his vivid description of contact with the kissing bug, triatomine, and by some of his symptoms in later life.6

cats, and guineapigs) and wild mammals (eg, rodents, marsupials, and armadillos) mainly by large, bloodsucking reduviid bugs of the subfamily Triatominae, within three overlapping cycles: domestic, peridomestic, and sylvatic.7 Although more than 130 species of triatominebugs have been identified, only a handful are competent vectors for T cruzi.8,9 Triatoma infestans, Rhodnius prolixus, and Triatoma dimidiata are the three most important vector species in the transmission of T cruzi to man.10,11 Historically, T infestans has been by far the most important vector, and has been the primary vector in sub-Amazonian endemic regions (southern South America). R prolixus istypically reported in northern South America and Central America, and T dimidiata occupies a similar area, but also extends further north into Mexico. Triatomines have five nymphal stages and adults of both sexes, all of which can harbour and transmit T cruzi. The probability that a triatomine is infected with T cruzi increases in accordance with the number of bloodmeals taken, so that older...