Commentary: Carlos Chagas—predecessor of Epidemiology in Brazil
Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
* Corresponding author. E-mail: jrcarval@fiocruz.br
Three contextual points should be borne in mind when considering the texts Carlos Chagas wrote in 19091–4as an example of a significant contribution to epidemiology. First, even though its roots extend back to classical ancient history with the work of Hippocrates, epidemiology was only acknowledged as an academic discipline in the 20th century. Second, Chagas was not the only contributor. The method implemented in the early days of Manguinhos followed the ‘Pasteur model’ that spread throughout the world at the time. In America, Garcia5 pointed out that almost all scientific institutes founded at the turn of the century adopted this paradigm: they sought solutions for defined problems in society; and they equated these socially determined problems with scientific freedom at institutions in which the ‘Pasteur model’ was followed. They also linked basic research, still in its early stage of development, with applied research and production. This could mean an anti-plague serum or a vaccine, or even a process for screening windows and using mosquito nets to prevent insects from transmitting disease agents. Similar research models can be found at scientific institutes where the study of agriculture and cattle farming is undertaken. Finally, in a third epistemic context: creating relevant knowledge by using a special thought process did not necessarily require being identified as a specific discipline. This applied to the writings of Carlos Chagas, and particularly, to the school of Manguinhos in the early 20th century. If we consider our current methodological tools, the discoveries of the time had all the necessary features to be classified as epidemiological. This is confirmed by even a superficial reading of Carlos Chagas’ articles.
The major recognition of the epidemiological meaning of Carlos Chagas's work came with his inclusion in the compendium ‘The Challenge of Epidemiology’ published by PAHO in 1988.6 When asked to nominate the ten most important texts of all times in epidemiology almost a hundred American and European epidemiologists declared his work to be ‘pioneering’.
Over the years, researchers of Chagas's "new morbid entity" has always taken an epidemiological approach. In the Introduction of his mathematical model for malaria, MacDonald7 proposes a historical sequence of Epidemiology. From an initial, ‘merely circumstantial’ model, he proceeds with the theory of the germ and the discovery of vectors, to a biological model in which the cycles of parasites dominate the scenario. In order to overcome the weaknesses of both models, he proposes a mathematical model which he adopts in his analysis. Mac Donald does not make any reference to the social model that emerged in the second half of the 20th century. From this perspective, Chagas and his colleagues at the time of Manguinhos were still immersed in the biological model proposed by Mac Donald.
In her comments on Morris’ book ‘Uses of Epidemiology’,8 Ann Oakley9 gives the date of publication of this seminal work as being immediately after the end of the Second World War. The work of Chagas comes close in many ways to each one of the ‘seven uses’ described by Morris. In particular, it adopts an epidemiological way of thinking while estimating risks, indicating ‘the cause’ and completing the clinical picture of this new disease. Chagas was ahead of his time. He writes of the ‘choking ailment’, describing the megaesophagus that, along with heart disease and megacolon, dominates the pathology of the disease as we know it today.
Chagas introduces a way of thinking that was later adopted in new circumstances as, for example, by Fritz Koeberle.10 This Austrian pathologist had never performed an autopsy of the megacolon nor of the megaesophagus during his long career in Europe. When he arrived in Brazil, he saw dozens of cases in the Ribeirão Preto region and immediately associated them with the Chagas disease prevalent in this area. In this same major centre of research into Chagas disease, Mauro Pereira Barreto induced Silva to produce important material that described the history of the Chagas endemic in the State of São Paulo from the middle of the 19th century, using an epidemiological (social) method that incorporated concepts of geography.11 Barreto points out the absence of any mention of the indigenous insect called ‘barbeiro’ by European naturalists in trips to the heart of the country in the 19th century. He then formulates the hypothesis that the invasion of the primitive huts (choupana) by the insect is passive and does not comply with the assumption that it is a direct result of putting down a natural forest.12
Neither the controversy that happened back then, nor the academic dispute which arose about the clinical nature of the discovery, needs to be detailed here.13 However, such disputes reflected the resistance of some physicians in the medical field who resented the power and interference of representatives of experimental medicine (more precisely of the Manguinhos researchers), especially in terms of teaching, and on public health in general.14
In order to achieve the difficult task of understanding the full lifecycle of the parasite, Chagas employed a way of thinking that can nowadays be described as epidemiological. In his pursuit of the elements of this cycle, Chagas focused on the fact that the parasite ‘barbeiro’ lived in human dwellings. This led to the preliminary conclusion that men and domestic pets were probably the definitive hosts. Today we know that it is uncommon to find trypanosomes in the blood of chronic Chagas disease patients. However, although he was right in the clinical description of the disease, ultimately Chagas made mistakes in his search for the link in the chain, of which the most often criticized was the association of the prevalent goiter in the region to the trypanosome infection.15
Also noteworthy is the fact that, in 1916, Chagas described the ‘eye and eyelid affections’ in their acute form. However, he interpreted such signs in association with myxoedema due to hypothyroidism, assigning it a different meaning from the one given later by Romaña and Mazza.16
However, these mistakes are not particularly important compared with the merit of the discovery, which is of great social and scientific importance, in addition to representing an advance in Brazilian and South American research. The modernity of molecular epidemiology, evidence based medicine and translational medicine makes us think about how knowledge was built in the case of Chagas disease. Even without modern technology, the process for discovering Chagas disease back then was similar to today in the close interaction between basic work in the lab, at the bedside and in the field. It was and is ‘translational’ in its essence and even the controversy surrounding the existence of the disease and its false association with the epidemiology of goiter contributed to the greatness of the work of this Brazilian scientist and his discovery which reaches its centenery in 2009.
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1 Chagas C. Nova tripanosomíase humana. Mem Inst Oswaldo Cruz (1909) 160.
2 Chagas C. Neue Trypanosomen. Archiv F. u. Tropenhygiene (1909) 13.
3 Chagas C. Nouvelle espèce de trypanosomiase humaine. Bulletin de la Societé de Pathologie Exotique (1909) 2:6.
4 Chagas C. Nova espécie mórbida do homem, produzida por um tripanossomo Trypanosoma cruzi. Brazil Médico. (1909) 23:16.
5 Garcia JC. Historia de las instituciones de investigación en salud en América Latina: 1880–1930. Educ Méd Salud (1981) 15:88.
6 Buck C, Llopis A, Nájera E, Terris M, eds. The Challenge of Epidemiology: Issues and Selected Readings. In: Publicación Científica N° 505 (1988) Washington DC: PAHO.
7 Mac Donald G. In: The Epidemiology and Control of Malaria (1957) London: Oxford University Press.
8 Morris JN. In: Uses of Epidemiology (1957) Edinburgh: E. & S. Livingston Ltd.
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10 Koeberle F. Patogenia do megaesôfago brasileiro e europeu. (1962) Tese para o concurso da cátedra de Patologia da Faculdade de Medicina de Ribeirão Preto – USP.
11 Silva LJ. A evolução da Doença de Chagas no Estado de São Paulo (1999) São Paulo: HUCITEC.
12 Carvalheiro JR. Os herdeiros do velho albatroz. Apresentação (in L.J.Silva A evolução da Doença de Chagas no Estado de São Paulo). (1999) São Paulo: HUCITEC.
13 Delaporte F. Chagas, a lógica e a descoberta. Manguinhos (1994) I:39–53.
14 Kropf S, Azevedo N, Ferreira LO. Biomedical research and public health in Brazil: the case of Chagas’ disease (1909–1950). Soc Hist Med (2003) 16:111–29.[Abstract]
15 Kropf S. Doença de Chagas, doença do Brasil: ciência, saúde e nação (1909–1962). (2006) 2 vols. Niterói: Universidade Federal Fluminense, Departamento de História.
16 Romana C. Acerca de un síntoma inicial de valor para el diagnóstico de la forma aguda de la enfermedad de Chagas. (1935) 22:16–25. La conjuntivitis schizotripanosómica unilateral (hipótesis sobre la puerta de entrada conjuntival de la enfermedad). Mision de Estudios de Patologia Regional Argentina (MEPRA).
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